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diff --git a/doc/sane.tex b/doc/sane.tex deleted file mode 100644 index 71ff6fc..0000000 --- a/doc/sane.tex +++ /dev/null @@ -1,1892 +0,0 @@ -\documentclass[11pt]{report} - -\usepackage{times,graphicx,url} -% Not Currently using changebar package so comment out to reduce -% external dependencies. -%\usepackage{changebar} - -\setlength{\parindent}{0pt} -\setlength{\parskip}{1.5ex plus 0.5ex minus 0.5ex} -\setlength{\textwidth}{6.5in} -\setlength{\textheight}{8.5in} -\setlength{\marginparwidth}{0pt} -\setlength{\oddsidemargin}{0pt} -\setlength{\evensidemargin}{0pt} -\setlength{\marginparsep}{0pt} -\addtolength{\topmargin}{-0.75in} - -\title{\huge SANE Standard Version 1.06} -\author{} -\date{2008-05-03} - -\makeindex - -\begin{document} - -\newcommand{\filename}[1]{{\tt #1}} -\newcommand{\code}[1]{{\tt #1}} -\newcommand{\var}[1]{{\it #1}} -\newcommand{\defn}[1]{#1\index{#1}} - -% Uncomment if adding changebars to text -%\begin{latexonly} -% \setcounter{changebargrey}{0} % black change bars -%\end{latexonly} - -\maketitle -\tableofcontents -\listoffigures -\listoftables - - -\chapter{Preface} - -The SANE standard is being developed by a group of free-software -developers. The process is open to the public and comments as well as -suggestions for improvements are welcome. Information on how to join -the SANE development process can be found in Chapter -\ref{chap:contact}. - -The SANE standard is intended to streamline software development by -providing a standard application programming interface to access -raster scanner hardware. This should reduce the number of different -driver implementations, thereby reducing the need for reimplementing -similar code. - - -\section{About This Document} - -This document is intended for developers who are creating either an -application that requires access to raster scanner hardware and for -developers who are implementing a SANE driver. It does not cover -specific implementations of SANE components. Its sole purpose is to -describe and define the SANE application interface that will enable -any application on any platform to interoperate with any SANE backend -for that platform. - -The remainder of this document is organized as follows. -Chapter~\ref{chap:intro} provides introductional material. -Chapter~\ref{chap:environ} presents the environment SANE is designed -for. Chapter~\ref{chap:api} details the SANE Application Programmer -Interface. Chapter~\ref{chap:net} specifies the network protocol that -can be used to implement the SANE API in a network transparent -fashion. Finally, Chapter~\ref{chap:contact} gives information on how -to join the SANE development process. - -\subsection{Typographic Conventions} - -Changes since the last revision of this document are highlighted -like this: - -% \begin{changebar} -% Paragraphs that changed since the last revision of the documention -% are marked like this paragraph. -% \end{changebar} - -\chapter{Introduction}\label{chap:intro} - -SANE is an application programming interface (API) that provides -standardized access to any raster image scanner hardware. The -standardized interface allows to write just one driver for each -scanner device instead of one driver for each scanner and application. -The reduction in the number of required drivers provides significant -savings in development time. More importantly, SANE raises the level -at which applications can work. As such, it will enable applications -that were previously unheard of in the UNIX world. While SANE is -primarily targeted at a UNIX environment, the standard has been -carefully designed to make it possible to implement the API on -virtually any hardware or operating system. - -SANE is an acronym for ``Scanner Access Now Easy.'' Also, the hope is -that SANE is sane in the sense that it will allow easy implementation -of the API while accommodating all features required by today's -scanner hardware and applications. Specifically, SANE should be broad -enough to accommodate devices such as scanners, digital still and -video cameras, as well as virtual devices like image file filters. - -\section{Terminology} - -An application that uses the SANE interface is called a SANE {\em - frontend}. A driver that implements the SANE interface is called a -SANE {\em backend}. A {\em meta backend\/} provides some means to -manage one or more other backends. - - -\chapter{The SANE Environment}\label{chap:environ} - -SANE is defined as a C-callable library interface. Accessing a raster -scanner device typically consists of two phases: first, various -controls of the scanner need to be setup or queried. In the second -phase, one or more images are acquired. - -Since the device controls are widely different from device to device, -SANE provides a generic interface that makes it easy for a frontend to -give a user access to all controls without having to understand each -and every device control. The design principle used here is to -abstract each device control into a SANE {\em option\/}. An option is -a self-describing name/value pair. For example, the brightness -control of a camera might be represented by an option called -\code{brightness} whose value is an integer in the range from 0 to -255. - -With self-describing options, a backend need not be concerned with -{\em presentation\/} issues: the backend simply provides a list of -options that describe all the controls available in the device. -Similarly, there are benefits to the frontend: it need not be -concerned with the {\em meaning\/} of each option. It simply provides -means to present and alter the options defined by the backend. - - -\section{Attaching to a SANE backend} - -The process through which a SANE frontend connects to a backend is -platform dependent. Several possibilities exist: -\begin{itemize} - -\item {\bf Static linking:} A SANE backend may be linked directly into - a frontend. While the simplest method of attaching to a backend, it - is somewhat limited in functionality since the available devices is - limited to the ones for which support has been linked in when the - frontend was built. But even so static linking can be quite useful, - particularly when combined with a backend that can access scanners - via a network. Also, it is possible to support multiple backends - simultaneously by implementing a meta backend that manages several - backends that have been compiled in such a manner that they export - unique function names. For example, a backend called \code{be} - would normally export a function called \code{sane\_read()}. If - each backend would provide such a function, static linking would - fail due to multiple conflicting definitions of the same symbol. - This can be resolved by having backend \code{be} include a - header file that has lines of the form: - \begin{quote} -\begin{verbatim} -#define sane_read be_sane_read -\end{verbatim} - \end{quote} - With definitions of this kind, backend \code{be} will export - function name \code{be\_sane\_read()}. Thus, all backends will - export unique names. As long as a meta backend knows about these - names, it is possible to combine several backends at link time and - select and use them dynamically at runtime. - -\item {\bf Dynamic linking:} A simpler yet more powerful way to - support multiple backends is to exploit dynamic linking on platforms - that support it. In this case, a frontend is linked against a - shared library that implements any SANE backend. Since each - dynamically linked backend exports the same set of global symbols - (all starting with the prefix \code{sane\_}), the dynamic library - that gets loaded at runtime does not necessarily have to be the same - one as one the frontend got linked against. In other words, it is - possible to switch the backend by installing the appropriate backend - dynamic library. - - More importantly, dynamic linking makes it easy to implement a meta - backend that loads other backends {\em on demand}. This is a - powerful mechanism since it allows adding new backends merely by - installing a shared library and updating a configuration file. - -\item {\bf Network connection:} Arguably the ultimate way to attach to - a scanner is by using the network to connect to a backend on a - remote machine. This makes it possible to scan images from any host - in the universe, as long as there is a network connection to that - host and provided the user is permitted to access that scanner. - -\end{itemize} - -\begin{figure}[htbp] - \begin{center} - \leavevmode - \includegraphics[width=\textwidth]{figs/hierarchy} - \caption{Example SANE Hiearchy} - \label{fig:hierarchy} - \end{center} -\end{figure} - -The above discussion lists just a few ways for frontends to attach to -a backend. It is of course possible to combine these solutions to -provide an entire hierarchy of SANE backends. Such a hierarchy is -depicted in Figure~\ref{fig:hierarchy}. The figure shows that machine -A uses a dynamic-linking based meta backend called \code{dll} to -access the backends called \code{pnm}, \code{mustek}, and \code{net}. -The first two are real backends, whereas the last one is a meta -backend that provides network transparent access to remote scanners. -In the figure, machine B provides non-local access to its scanners -through the SANE frontend called \code{saned}. The \code{saned} in -turn has access to the \code{hp} and \code{autolum} backends through -another instance of the \code{dll} backend. The \code{autolum} meta -backend is used to automatically adjust the luminance (brightness) of -the image data acquired by the camera backend called \code{qcam}. - -Note that a meta backend really is both a frontend and a backend at -the same time. It is a frontend from the viewpoint of the backends -that it manages and a backend from the viewpoint of the frontends that -access it. The name ``meta backend'' was chosen primarily because the -SANE standard describes the interface from the viewpoint of a (real) -frontend. - - -\section{Image Data Format}\label{sec:imageformat}\index{image data format} - -Arguably the most important aspect of an image acquisition system is -how images are represented. The SANE approach is to define a simple -yet powerful representation that is sufficient for vast majority of -applications and devices. While the representation is simple, the -interface has been defined carefully to allow extending it in the -future without breaking backwards compatibility. Thus, it will be -possible to accommodate future applications or devices that were not -anticipated at the time this standard was created. - -A SANE image is a rectangular area. The rectangular area is -subdivided into a number of rows and columns. At the intersection of -each row and column is a quadratic pixel. A pixel consists of one or -more sample values. Each sample value represents one channel (e.g., -the red channel). Each sample value has a certain bit depth. The bit -depth is fixed for the entire image and can be as small as one bit. -Valid bit depths are 1, 8, or 16 bits per sample. If a device's -natural bit depth is something else, it is up to the driver to scale -the sample values appropriately (e.g., a 4 bit sample could be scaled -by a factor of four to represent a sample value of depth 8). - -\subsection{Image Transmission} - -The SANE API transmits an image as a sequence of frames. Each frame -covers the same rectangular area as the entire image, but may contain -only a subset of the channels in the final image. For example, a -red/green/blue image could either be transmitted as a single frame -that contains the sample values for all three channels or it could be -transmitted as a sequence of three frames: the first frame containing -the red channel, the second the green channel, and the third the blue -channel. - -Conceptually, each frame is transmitted a byte at a time. Each byte -may contain 8 sample values (for an image bit depth of 1), one full -sample value (for an image bit depth of 8), or a partial sample value -(for an image bit depth of 16 or bigger). In the latter case, the -bytes of each sample value are transmitted in the machine's native -byte order. For depth 1, the leftmost pixel is stored in the most -significant bit, and the rightmost pixel in the least significant bit. -\begin{quote} - \begin{center} - {\bf Backend Implementation Note} - \end{center} - A network-based meta backend will have to ensure that the byte order - in image data is adjusted appropriately if necessary. For example, - when the meta backend attaches to the server proxy, the proxy may - inform the backend of the server's byte order. The backend can then - apply the adjustment if necessary. In essence, this implements a - ``receiver-makes-right'' approach. -\end{quote} - -\begin{figure}[htbp] - \begin{center} - \leavevmode - \includegraphics[width=0.5\textwidth]{figs/xfer} - \caption{Transfer order of image data bytes} - \label{fig:xfer} - \end{center} -\end{figure} - -The order in which the sample values in a frame are transmitted is -illustrated in Figure~\ref{fig:xfer}. As can be seen, the values are -transmitted row by row and each row is transmitted from left-most to -right-most column. The left-to-right, top-to-bottom transmission -order applies when the image is viewed in its normal orientation (as -it would be displayed on a screen, for example). - -If a frame contains multiple channels, then the channels are -transmitted in an interleaved fashion. Figure~\ref{fig:pixels} -illustrates this for the case where a frame contains a complete -red/green/blue image with a bit-depth of 8. For a bit depth of 1, -each byte contains 8 sample values of a {\em single\/} channel. In -other words, a bit depth 1 frame is transmitted in a byte interleaved -fashion. - -\begin{figure}[htbp] - \begin{center} - \leavevmode - \includegraphics[width=0.8\textwidth]{figs/image-data} - \caption{Bit and byte order or image data} - \label{fig:pixels} - \end{center} -\end{figure} - -When transmitting an image frame by frame, the frontend needs to know -what part of the image a frame represents (and how many frames it -should expect). For that purpose, the SANE API tags every frame with -a type. This version of the SANE standard supports the following -frame types: -\begin{quote} -\begin{description} - -\item[\code{\defn{SANE\_FRAME\_GRAY}}:] The frame contains a single - channel of data that represents sample values from a spectral band - that covers the human visual range. The image consists of this - frame only. - -\item[\code{\defn{SANE\_FRAME\_RGB}}:] The frame contains three - channels of data that represent sample values from the red, green, - and blue spectral bands. The sample values are interleaved in the - order red, green, and blue. The image consists of this frame only. - -\item[\code{\defn{SANE\_FRAME\_RED}}:] The frame contains one channel - of data that represents sample values from the red spectral band. - The complete image consists of three frames: - \code{SANE\_\-FRA\-ME\_RED}, \code{SANE\_FRAME\_GREEN}, and - \code{SANE\_FRAME\_BLUE}. The order in which the frames are - transmitted chosen by the backend. - -\item[\code{\defn{SANE\_FRAME\_GREEN}}:] The frame contains one - channel of data that represents sample values from the green - spectral band. The complete image consists of three frames: - \code{SANE\_\-FRA\-ME\_RED}, \code{SANE\_FRAME\_GREEN}, and - \code{SANE\_FRAME\_BLUE}. The order in which the frames are - transmitted chosen by the backend. - -\item[\code{\defn{SANE\_FRAME\_BLUE}}:] The frame contains one channel - of data that represents sample values from the blue spectral band. - The complete image consists of three frames: - \code{SANE\_\-FRA\-ME\_RED}, \code{SANE\_FRAME\_GREEN}, and - \code{SANE\_FRAME\_BLUE}. The order in which the frames are - transmitted chosen by the backend. - -\end{description} -\end{quote} - -In frames of type \code{SANE\_FRAME\_GRAY}, when the bit depth is 1 there are -only two sample values possible, 1 represents minimum intensity -(black) and 0 represents maximum intensity (white). For all other bit -depth and frame type combinations, a sample value of 0 represents -minimum intensity and larger values represent increasing intensity. - -The combination of bit depth 1 and \code{SANE\_FRAME\_RGB} (or -\code{SANE\_FRAME\_RED}, \code{SANE\_FRAME\_GREEN}, \code{SANE\_FRAME\_BLUE}) -is rarely used and may not be supported by every frontend. - -\chapter{The SANE Application Programmer Interface (API)}\label{chap:api} - -This Section defines version 1 of the SANE application -programmer interface (API). Any SANE frontend must depend on the -interface defined in this section only. Converseley, any SANE backend -must implement its functionality in accordance with this -specification. The interface as documented here is declared as a C -callable interface in a file called \filename{sane/sane.h}. This file should -normally be included via a C pre-processor directive of the form: -\begin{verbatim} - #include <sane/sane.h> -\end{verbatim} - - -\section{Version Control} - -The SANE standard is expected to evolve over time. Whenever a change -to the SANE standard is made that may render an existing frontend or -backend incompatible with the new standard, the major version number -must be increased. Thus, any frontend/backend pair is compatible -provided the major version number of the SANE standard they implement -is the same. A frontend may implement backwards compatiblity by -allowing major numbers that are smaller than the expected major number -(provided the frontend really can cope with the older version). In -contrast, a backend always provides support for one and only one -version of the standard. If a specific application does require that -two different versions of the same backend are accessible at the same -time, it is possible to do so by installing the two versions under -different names. - -SANE version control also includes a minor version number and a build -revision. While control of these numbers remains with the implementor -of a backend, the recommended use is as follows. The minor version is -incremented with each official release of a backend. The build -revision is increased with each build of a backend. - -The SANE API provides the following five macros to manage version -numbers. -\begin{quote} - \begin{description} - \item[\code{\defn{SANE\_CURRENT\_MAJOR}}:] The value of this macro is the - number of the SANE standard that the interface implements. - - \item[\code{\defn{SANE\_VERSION\_CODE}(\var{maj},\var{min},\var{bld})}:] - \label{sec:saneversioncode} - This macro can be used to build a monotonically increasing version - code. A SANE version code consists of the SANE standard major - version number (\var{maj}), the minor version number \var{min}, - and the build revision of a backend (\var{bld}). The major and - minor version numbers must be in the range 0\ldots255 and the - build revision must be in the range 0\ldots65535. - - Version codes are monotonic in the sense that it is possible to - apply relational operators (e.g., equality or less-than test) - directly on the version code rather than individually on the three - components of the version code. - - Note that the major version number alone determines whether a - frontend/backend pair is compatible. The minor version and the - build revision are used for informational and bug-fixing purposes - only. - - \item[\code{\defn{SANE\_VERSION\_MAJOR}(\var{vc})}:] This macro returns the - major version number component of the version code passed in - argument \var{vc}. - \item[\code{SANE\_VERSION\_MINOR(\var{vc})}:] This macro returns the - minor version number component of the version code passed in - argument \var{vc}. - \item[\code{SANE\_VERSION\_BUILD(\var{vc})}:] This macro returns the - build revision component of the version code passed in argument - \var{vc}. - \end{description} -\end{quote} - - -\section{Data Types} - -\subsection{Base Types} - -The SANE standard is based on just two SANE-specific base types: the -SANE byte and word. -\begin{quote} - \code{typedef \var{some-scalar-type\/} \defn{SANE\_Byte};} \\ - \code{typedef \var{some-scalar-type\/} \defn{SANE\_Word};} -\end{quote} -\verb|SANE_Byte| must correspond to some scalar C type that is capable -of holding values in the range 0 to 255. \verb|SANE_Word| must be -capable of holding any of the following: -\begin{itemize} - \item the truth values \verb|SANE_FALSE| and \verb|SANE_TRUE| - \item signed integers in the range $-2^{31}\ldots2^{31}-1$ - \item fixed point values in the range $-32768\ldots32767.9999$ with - a resolution of $1/65536$ - \item 32 bits (for bit sets) -\end{itemize} -Note that the SANE standard does not define what C type -\verb|SANE_Byte| and \verb|SANE_Word| map to. For example, on some -platforms, the latter may map to \verb|long int| whereas on others it -may map to \verb|int|. A portable SANE frontend or backend must -therefore not depend on a particular mapping. - -\subsection{Boolean Type} - -\code{\defn{SANE\_Bool}} is used for variables that can take one of -the two truth values \code{\defn{SANE\_FALSE}} and -\code{\defn{SANE\_TRUE}}. The former value is defined to be 0, -whereas the latter is 1.\footnote{This is different from ANSI C where - any non-zero integer value represents logical TRUE.} The C -declarations for this type are given below. -\begin{quote} -\begin{verbatim} -#define SANE_FALSE 0 -#define SANE_TRUE 1 -typedef SANE_Word SANE_Bool; -\end{verbatim} -\end{quote} -Note that \verb|SANE_Bool| is simply an alias of \verb|SANE_Word|. It -is therefore always legal to use the latter type in place of the -former. However, for clarity, it is recommended to use -\verb|SANE_Bool| whenever a given variable or formal argument has a -fixed interpretation as a boolean object. - -\subsection{Integer Type} - -\code{\defn{SANE\_Int}} is used for variables that can take integer -values in the range $-2^{32}$ to $2^{31}-1$. Its C declaration is -given below. -\begin{quote} -\begin{verbatim} -typedef SANE_Word SANE_Int; -\end{verbatim} -\end{quote} -Note that \verb|SANE_Int| is simply an alias of \verb|SANE_Word|. It -is therefore always legal to use the latter type in place of the -former. However, for clarity, it is recommended to use -\verb|SANE_Int| whenever a given variable or formal argument has a -fixed interpretation as an integer object. - - -\subsection{Fixed-point Type} - -\code{\defn{SANE\_Fixed}} is used for variables that can take fixed -point values in the range $-32768$ to $32767.9999$ with a resolution -of $1/65535$. The C declarations relating to this type are given -below. -\begin{quote} -\begin{verbatim} -#define SANE_FIXED_SCALE_SHIFT 16 -typedef SANE_Word SANE_Fixed; -\end{verbatim} -\end{quote} -The macro \code{\defn{SANE\_FIXED\_SCALE\_SHIFT}} gives the location -of the fixed binary point. This standard defines that value to be 16, -which yields a resolution of $1/65536$. - -Note that \verb|SANE_Fixed| is simply an alias of \verb|SANE_Word|. -It is therefore always legal to use the latter type in place of the -former. However, for clarity, it is recommended to use -\verb|SANE_Fixed| whenever a given variable or formal argument has a -fixed interpretation as a fixed-point object. - -For convenience, SANE also defines two macros that convert fixed-point -values to and from C double floating point values. -\begin{quote} - \begin{description} - - \item[\code{\defn{SANE\_FIX}(\var{d})}:] Returns the largest SANE - fixed-point value that is smaller than the double value \var{d}. - No range checking is performed. If the value of \var{d} is out of - range, the result is undefined. - - \item[\code{\defn{SANE\_UNFIX}(\var{w})}:] Returns the nearest - double machine number that corresponds to fixed-point value - \var{w}. - - \end{description} -\end{quote} -SANE does {\em not\/} require that the following two expressions hold -true (even if the values of \var{w} and \var{d} are in range): -\begin{quote} -\begin{verbatim} -SANE_UNFIX(SANE_FIX(d)) == d -SANE_FIX(SANE_UNFIX(w)) == w -\end{verbatim} -\end{quote} -In other words, conversion between fixed and double values may be -lossy. It is therefore recommended to avoid repeated conversions -between the two representations. - - -\subsection{Text} - -\subsubsection{Character Type} - -Type \code{\defn{SANE\_Char}} represents a single text character or -symbol. At present, this type maps directly to the underlying C -\verb|char| type (typically one byte). The encoding for such -characters is currently fixed as ISO LATIN-1. Future versions of this -standard may map this type to a wider type and allow multi-byte -encodings to support internationalization. As a result of this, care -should be taken to avoid the assumption that -\verb|sizeof(SANE_Char)==sizeof(char)|. -\begin{quote} -\begin{verbatim} -typedef char SANE_Char; -\end{verbatim} -\end{quote} - -\subsubsection{String Type} - -Type \code{\defn{SANE\_String}} represents a text string as a sequence -of C \verb|char| values. The end of the sequence is indicated by a -\verb|'\0'| (\defn{NUL}) character. -\begin{quote} -\begin{verbatim} -typedef SANE_Char *SANE_String; -typedef const SANE_Char *SANE_String_Const; -\end{verbatim} -\end{quote} -The type \code{\defn{SANE\_String\_Const}} is provided by SANE to -enable declaring strings whose contents is unchangable. Note that in -ANSI C, the declaration -\begin{quote} -\begin{verbatim} -const SANE_String str; -\end{verbatim} -\end{quote} -declares a string pointer that is constant (not a string pointer that -points to a constant value). - - -\subsection{Scanner Handle Type} - -Access to a scanner is provided through an opaque type called -\code{\defn{SANE\_Handle}}. The C declaration of this type is given -below. -\begin{quote} -\begin{verbatim} -typedef void *SANE_Handle; -\end{verbatim} -\end{quote} -While this type is declared to be a void pointer, an application must -not attempt to interpret the value of a \verb|SANE_Handle|. In -particular, SANE does not require that a value of this type is a legal -pointer value. - - -\subsection{Status Type} - -Most SANE operations return a value of type \code{\defn{SANE\_Status}} -to indicate whether the completion status of the operation. If an -operation completes successfully, \verb|SANE_STATUS_GOOD| is returned. -In case of an error, a value is returned that indicates the nature of -the problem. The complete list of available status codes is listed in -Table \ref{tab:status}. It is recommended to use function -\code{sane\_strstatus()} to convert status codes into a legible -string. - -\begin{table}[htbp] - \begin{center} - \begin{tabular}{|l|r|l|} - \hline - \multicolumn{1}{|c|}{\bf Symbol} & \multicolumn{1}{c|}{\bf Code} & - \multicolumn{1}{c|}{\bf Description} \\ - \hline\hline -\code{\defn{SANE\_STATUS\_GOOD}} - & 0 & Operation completed succesfully. \\ -\code{\defn{SANE\_STATUS\_UNSUPPORTED}} - & 1 & Operation is not supported. \\ -\code{\defn{SANE\_STATUS\_CANCELLED}} - & 2 & Operation was cancelled. \\ -\code{\defn{SANE\_STATUS\_DEVICE\_BUSY}} - & 3 & Device is busy---retry later. \\ -\code{\defn{SANE\_STATUS\_INVAL}} - & 4 & Data or argument is invalid. \\ -\code{\defn{SANE\_STATUS\_EOF}} - & 5 & No more data available (end-of-file). \\ -\code{\defn{SANE\_STATUS\_JAMMED}} - & 6 & Document feeder jammed. \\ -\code{\defn{SANE\_STATUS\_NO\_DOCS}} - & 7 & Document feeder out of documents. \\ -\code{\defn{SANE\_STATUS\_COVER\_OPEN}} - & 8 & Scanner cover is open. \\ -\code{\defn{SANE\_STATUS\_IO\_ERROR}} - & 9 & Error during device I/O. \\ -\code{\defn{SANE\_STATUS\_NO\_MEM}} - & 10 & Out of memory. \\ -\code{\defn{SANE\_STATUS\_ACCESS\_DENIED}} - & 11 & Access to resource has been denied. \\ - \hline - \end{tabular} - \caption{Status Codes}\label{tab:status} - \end{center} -\end{table} - - -\subsection{Device Descriptor Type} - -Each SANE device is represented by a structure of type -\code{\defn{SANE\_Device}}. The C declaration of this type is given -below. -\begin{quote} -\begin{verbatim} -typedef struct - { - SANE_String_Const name; - SANE_String_Const vendor; - SANE_String_Const model; - SANE_String_Const type; - } -SANE_Device; -\end{verbatim} -\end{quote} -\index{device-name} -The structure provides the unique name of the scanner in member -\code{name}. It is this unique name that should be passed in a call -to \code{sane\_open()}. The format of this name is completely up to -the backend. The only constraints are that the name is unique among -all devices supported by the backend and that the name is a legal SANE -text string. To simplify presentation of unique names, their length -should not be excessive. It is {\em recommended\/} that backends keep -unique names below 32 characters in length. However, applications -{\em must\/} be able to cope with arbitrary length unique names. - -The remaining members in the device structure provide additional -information on the device corresponding to the unique name. -Specifically, members \code{vendor}, \code{model}, and \code{type} are -single-line strings that give information on the vendor -(manufacturer), model, and the type of the device. For consistency's -sake, the following strings should be used when appropriate (the lists -will be expanded as need arises): - -\begin{table}[htbp] - \begin{center} - \leavevmode - \hspace{\fill} - \begin{tabular}[t]{|ll|} - \hline - \multicolumn{2}{|c|}{\bf \defn{Vendor Strings}} \\ - \hline\hline - \code{AGFA} & \code{Microtek} \\ - \code{Abaton} & \code{Minolta} \\ - \code{Acer} & \code{Mitsubishi} \\ - \code{Apple} & \code{Mustek} \\ - \code{Artec} & \code{NEC} \\ - \code{Avision} & \code{Nikon} \\ - \code{CANON} & \code{Plustek} \\ - \code{Connectix} & \code{Polaroid} \\ - \code{Epson} & \code{Relisys} \\ - \code{Fujitsu} & \code{Ricoh} \\ - \code{Hewlett-Packard} & \code{Sharp} \\ - \code{IBM} & \code{Siemens} \\ - \code{Kodak} & \code{Tamarack} \\ - \code{Lexmark} & \code{UMAX} \\ - \code{Logitech} & \code{Noname} \\ - \hline - \end{tabular} - \hspace{\fill} - \begin{tabular}[t]{|l|} - \hline - \multicolumn{1}{|c|}{\bf \defn{Type Strings}} \\ - \hline\hline - \code{film scanner} \\ - \code{flatbed scanner} \\ - \code{frame grabber} \\ - \code{handheld scanner} \\ - \code{multi-function peripheral} \\ - \code{sheetfed scanner} \\ - \code{still camera} \\ - \code{video camera} \\ - \code{virtual device} \\ - \hline - \end{tabular} - \hspace{\fill} - \caption{Predefined Device Information Strings} - \label{tab:devinfo} - \end{center} -\end{table} -Note that vendor string \code{Noname} can be used for virtual devices -that have no physical vendor associated. Also, there are no -predefined model name strings since those are vendor specific and -therefore completely under control of the respective backends. - - -\subsection{Option Descriptor Type}\label{sec:odesc} - -Option descriptors are at the same time the most intricate and -powerful type in the SANE standard. Options are used to control -virtually all aspects of device operation. Much of the power of the -SANE API stems from the fact that most device controls are completely -described by their respective option descriptor. Thus, a frontend can -control a scanner abstractly, without requiring knowledge as to what -the purpose of any given option is. Conversely, a scanner can -describe its controls without requiring knowledge of how the frontend -operates. The C declaration of the -\code{\defn{SANE\_Option\_Descriptor}} type is given below. -\begin{quote} -\begin{verbatim} -typedef struct - { - SANE_String_Const name; - SANE_String_Const title; - SANE_String_Const desc; - SANE_Value_Type type; - SANE_Unit unit; - SANE_Int size; - SANE_Int cap; - SANE_Constraint_Type constraint_type; - union - { - const SANE_String_Const *string_list; - const SANE_Word *word_list; - const SANE_Range *range; - } - constraint; - } -SANE_Option_Descriptor; -\end{verbatim} -\end{quote} - -\subsubsection{Option Name} - -Member \code{name} is a string that uniquely identifies the option. -The name must be unique for a given device (i.e., the option names -across different backends or devices need not be unique). The option -name must consist of lower-case ASCII letters (\code{a}--\code{z}), -digits (\code{0}--\code{9}), or the dash character (\code{-}) only. -The first character must be a lower-case ASCII character (i.e., not a -digit or a dash). - -\subsubsection{Option Title} - -Member \code{title} is a single-line string that can be used by the -frontend as a title string. This should typically be a short (one or -two-word) string that is chosen based on the function of the option. - -\subsubsection{Option Description} - -Member \code{desc} is a (potentially very) long string that can be -used as a help text to describe the option. It is the responsibility -of the frontend to break the string into managable-length lines. -Newline characters in this string should be interpreted as paragraph -breaks. - -\subsubsection{Option Value Type} - -Member \code{type} specifies the type of the option value. The -possible values for type \code{\defn{SANE\_Value\_Type}} are described -in Table \ref{tab:valuetype}. - -\begin{table}[htbp] - \begin{center} - \leavevmode - \begin{tabular}{|l|l|p{0.6\textwidth}|} -\hline -\multicolumn{1}{|c|}{\bf Symbol} & -\multicolumn{1}{c|}{\bf Code} & -\multicolumn{1}{c|}{\bf Description} \\ -\hline\hline - -\code{\defn{SANE\_TYPE\_BOOL}} & 0 & Option value is of type - \verb|SANE_Bool|. \\ - -\code{\defn{SANE\_TYPE\_INT}} & 1 & Option value is of type - \verb|SANE_Int|. \\ - -\code{\defn{SANE\_TYPE\_FIXED}}&2 & Option value is of type - \verb|SANE_Fixed|. \\ - -\code{\defn{SANE\_TYPE\_STRING}}&3 & Option value is of type - \verb|SANE_String|. \\ - -\code{\defn{SANE\_TYPE\_BUTTON}} & 4 & An option of this type has no value. -Instead, setting an option of this type has an option-specific -side-effect. For example, a button-typed option could be used by a -backend to provide a means to select default values or to the tell an -automatic document feeder to advance to the next sheet of paper. \\ - -\code{\defn{SANE\_TYPE\_GROUP}} & 5 & An option of this type has no value. -This type is used to group logically related options. A group option -is in effect up to the point where another group option is encountered -(or up to the end of the option list, if there are no other group -options). For group options, only members \code{title} and -\code{type} are valid in the option descriptor. \\ - - \hline - \end{tabular} - \caption{Option Value Types (\code{SANE\_Value\_Type})} - \label{tab:valuetype} - \end{center} -\end{table} - -\subsubsection{Option Value Unit} - -Member \code{unit} specifies what the physical unit of the option -value is. The possible values for type \code{\defn{SANE\_U\-nit}} are -described in Table \ref{tab:units}. Note that the specified unit is -what the SANE backend expects. It is entirely up to a frontend as to -how these units a presented to the user. For example, SANE expresses -all lengths in millimeters. A frontend is generally expected to -provide appropriate conversion routines so that a user can express -quantities in a customary unit (e.g., inches or centimeters). - -\begin{table}[htbp] - \begin{center} - \leavevmode - \begin{tabular}{|l|l|l|} -\hline -\multicolumn{1}{|c|}{\bf Symbol} & -\multicolumn{1}{|c|}{\bf Code} & -\multicolumn{1}{|c|}{\bf Description} \\ - -\hline\hline - -\code{\defn{SANE\_UNIT\_NONE}} & 0 & Value is unit-less (e.g., page count).\\ -\code{\defn{SANE\_UNIT\_PIXEL}} & 1 & Value is in number of pixels. \\ -\code{\defn{SANE\_UNIT\_BIT}} & 2 & Value is in number of bits. \\ -\code{\defn{SANE\_UNIT\_MM}} & 3 & Value is in millimeters. \\ -\code{\defn{SANE\_UNIT\_DPI}} & 4 & Value is a resolution in dots/inch. \\ -\code{\defn{SANE\_UNIT\_PERCENT}}& 5 & Value is a percentage. \\ -\code{\defn{SANE\_UNIT\_MICROSECOND}}& 6 & Value is time in $\mu$-seconds. \\ - -\hline - \end{tabular} - \caption{Physical Units (\code{SANE\_Unit})} - \label{tab:units} - \end{center} -\end{table} - -\subsubsection{Option Value Size}\label{sec:valuesize} - -Member \code{size} specifies the size of the option value (in bytes). -This member has a slightly different interpretation depending on the -type of the option value: -\begin{quote} - \begin{description} - \item[\code{SANE\_TYPE\_STRING}:] The size is the maximum size of - the string. For the purpose of string size calcuations, the - terminating \code{NUL} character is considered to be part of the - string. Note that the terminating \code{NUL} character must - always be present in string option values. - \item[\code{SANE\_TYPE\_INT}, \code{SANE\_TYPE\_FIXED}:] The size - must be a positive integer multiple of the size of a - \verb|SANE_Word|. The option value is a vector of length - \[ \code{size}/\code{sizeof(SANE\_Word)}. \] - \item[\code{SANE\_TYPE\_BOOL}:] The size must be set to - \code{sizeof(SANE\_Word)}. - \item[\code{SANE\_TYPE\_BUTTON}, \code{SANE\_TYPE\_GROUP}:] The - option size is ignored. - \end{description} -\end{quote} - -\subsubsection{Option Capabilities} - -Member \code{cap} describes what capabilities the option posseses. -This is a bitset that is formed as the inclusive logical OR of the -capabilities described in Table \ref{tab:capabilities}. The SANE API -provides the following to macros to test certain features of a given -capability bitset: -\begin{quote} - \begin{description} - - \item[\code{\defn{SANE\_OPTION\_IS\_ACTIVE}(\var{cap})}:] This macro - returns \code{SANE\_TRUE} if and only if the option with the - capability set \var{cap} is currently active. - - \item[\code{\defn{SANE\_OPTION\_IS\_SETTABLE}(\var{cap})}:] This - macro returns \code{SANE\_TRUE} if and only if the option with the - capability set \var{cap} is software settable. - \end{description} -\end{quote} - -\begin{table}[htbp] - \begin{center} - \leavevmode - \begin{tabular}{|l|r|p{0.59\textwidth}|} -\hline -\multicolumn{1}{|c|}{\bf Symbol} & -\multicolumn{1}{c|}{\bf Code} & -\multicolumn{1}{c|}{\bf Description} \\ -\hline\hline - -\code{\defn{SANE\_CAP\_SOFT\_SELECT}} & 1 & The option - value can be set by a call to \code{sane\_con\-trol\_opt\-ion()}.\\ - -\code{\defn{SANE\_CAP\_HARD\_SELECT}} & 2 & The option value can be set by - user-intervention (e.g., by flipping a switch). The user-interface - should prompt the user to execute the appropriate action to set such - an option. This capability is mutually exclusive with - SANE\_CAP\_SOFT\_SELECT (either one of them can be set, but not both - simultaneously). \\ - -\code{\defn{SANE\_CAP\_SOFT\_DETECT}} & 4 & The option - value can be detected by software. If - \code{SANE\_\-CAP\_\-SO\-FT\_SEL\-ECT} is set, this capability {\em must\/} - be set. If \code{SANE\_CAP\_HARD\_SELECT} is set, this capability - may or may not be set. If this capability is set but neither - \code{SANE\_CAP\_SO\-FT\_SEL\-ECT} nor \code{SANE\_CAP\_HA\-RD\_SEL\-ECT} - are, then there is no way to control the option. That is, the - option provides read-out of the current value only. \\ - -\code{\defn{SANE\_CAP\_EMULATED}} & 8 & If set, this capability indicates - that an option is not directly supported by the device and is - instead emulated in the backend. A sophisticated frontend may - elect to use its own (presumably better) emulation in lieu of an emulated - option. \\ - -\code{\defn{SANE\_CAP\_AUTOMATIC}} & 16 & If set, this capability indicates - that the backend (or the device) is capable to picking a reasonable - option value automatically. For such options, it is possible to - select automatic operation by calling \code{sane\_control\_option()} - with an action value of \code{SANE\_ACTION\_SET\_AUTO}. \\ - -\code{\defn{SANE\_CAP\_INACTIVE}} & 32 & If set, this capability indicates - that the option is not currently active (e.g., because it's - meaningful only if another option is set to some other value). \\ - -\code{\defn{SANE\_CAP\_ADVANCED}} & 64 & - If set, this capability indicates that the option should be - considered an ``advanced user option.'' A frontend typically - displays such options in a less conspicuous way than regular options - (e.g., a command line interface may list such options last or a - graphical interface may make them available in a seperate ``advanced - settings'' dialog). - \\ - -\hline - \end{tabular} - \caption{Option Capabilities} - \label{tab:capabilities} - \end{center} -\end{table} - -\subsubsection{Option Value Constraints} - -It is often useful to constrain the values that an option can take. -For example, constraints can be used by a frontend to determine how to -represent a given option. Member \code{constraint\_type} indicates -what constraint is in effect for the option. The constrained values -that are allowed for the option are described by one of the union -members of member \code{constraint}. The possible values of type -\code{\defn{SANE\_Constraint\_Type}} and the interpretation of the -\code{constraint} union is described in Table~\ref{tab:constraints}. - -\begin{table}[htbp] - \begin{center} - \leavevmode - \begin{tabular}{|l|r|p{0.5\textwidth}|} -\hline -\multicolumn{1}{|c|}{\bf Symbol} & -\multicolumn{1}{|c|}{\bf Code} & -\multicolumn{1}{|c|}{\bf Description} \\ - -\hline\hline - -\code{\defn{SANE\_CONSTRAINT\_NONE}} & 0 & The value is unconstrained. - The option can take any of the values possible for the option's - type. \\ - - \code{\defn{SANE\_CONSTRAINT\_RANGE}} & 1 & This constraint is - applicable to integer and fixed-point valued options only. It - constrains the option value to a possibly quantized range of - numbers. Option descriptor member \code{constraint.range} points to - a range of the type \code{\defn{SANE\_Range}}. This type is illustrated - below: - \begin{quote} -\begin{verbatim} -typedef struct - { - SANE_Word min; - SANE_Word max; - SANE_Word quant; - } -SANE_Range; -\end{verbatim} - \end{quote} - All three members in this structure are interpreted according to the - option value type (\verb|SANE_TYPE_INT| or \verb|SANE_TYPE_FIXED|). - Members \code{min} and \code{max} specify the minimum and maximum - values, respectively. If member \code{quant} is non-zero, it - specifies the quantization value. If $l$ is the minimum value, $u$ - the maximum value and $q$ the (non-zero) quantization of a range, - then the legal values are $v=k\cdot q+l$ for all non-negative - integer values of $k$ such that $v<=u$. \\ - -\code{\defn{SANE\_CONSTRAINT\_WORD\_LIST}} & 2 & This constraint is applicable - to integer and fixed-point valued options only. It constrains the - option value to a list of numeric values. Option descriptor member - \code{constraint.word\_list} points to a list of words that - enumerates the legal values. The first element in that list is an - integer (\verb|SANE_Int|) that specifies the length of the list (not - counting the length itself). The remaining elements in the list are - interpreted according to the type of the option value - (\verb|SANE_TYPE_INT| or \verb|SANE_TYPE_FIXED|). \\ - -\code{\defn{SANE\_CONSTRAINT\_STRING\_LIST}} & 3 & This constraint is - applicable to string-valued options only. It constrains the option - value to a list of strings. The option descriptor member - \code{con\-strai\-nt.str\-ing\_list} points to a \code{NULL} terminated - list of strings that enumerate the legal values for the option - value. -\\\hline - \end{tabular} - \caption{Option Value Constraints} - \label{tab:constraints} - \end{center} -\end{table} - - -\section{Operations} - -\subsection{\code{sane\_init}} - -This function must be called before any other SANE function can be called. -The behavior of a SANE backend is undefined if this function is not called -first or if the status code returned by \code{sane\_init} is different from -\code{\defn{SANE\_STATUS\_GOOD}}. The version code of the backend is returned -in the value pointed to by \code{version\_code}. If that pointer is -\code{NULL}, no version code is returned. Argument \code{authorize} is either -a pointer to a function that is invoked when the backend requires -authentication for a specific resource or \code{NULL} if the frontend does not -support authentication. -\begin{quote}\index{sane\_init} -\begin{verbatim} -SANE_Status sane_init (SANE_Int * version_code, - SANE_Authorization_Callback authorize); -\end{verbatim} -\end{quote} - -The authorization function may be called by a backend in response to -any of the following calls: -\begin{quote} - \code{sane\_open}, \code{sane\_control\_option}, \code{sane\_start} -\end{quote} -If a backend was initialized without authorization function, then -authorization requests that cannot be handled by the backend itself -will fail automatically and the user may be prevented from accessing -protected resources. Backends are encouraged to implement means of -authentication that do not require user assistance. E.g., on a -multi-user system that authenticates users through a login process a -backend could automatically lookup the apporpriate password based on -resource- and user-name. - -The authentication function type has the following declaration: -\begin{quote}\index{SANE\_Authorization\_Callback} - \index{domain}\index{username}\index{password} -\begin{verbatim} -#define SANE_MAX_USERNAME_LEN 128 -#define SANE_MAX_PASSWORD_LEN 128 - -typedef void (*SANE_Authorization_Callback) - (SANE_String_Const resource, - SANE_Char username[SANE_MAX_USERNAME_LEN], - SANE_Char password[SANE_MAX_PASSWORD_LEN]); -\end{verbatim} -\end{quote} -Three arguments are passed to the authorization function: -\code{resource} is a string specifying the name of the resource that -requires authorization. A frontend should use this string to build a -user-prompt requesting a username and a password. The \code{username} -and \code{password} arguments are (pointers to) an array of -\code{SANE\_MAX\_USERNAME\_LEN} and \code{SANE\_MAX\_PASSWORD\_LEN} -characters, respectively. The authorization call should place the -entered username and password in these arrays. The returned strings -{\em must\/} be ASCII-NUL terminated. - -\subsection{\code{sane\_exit}} - -This function must be called to terminate use of a backend. The -function will first close all device handles that still might be open -(it is recommended to close device handles explicitly through a call -to \code{sane\_clo\-se()}, but backends are required to release all -resources upon a call to this function). After this function returns, -no function other than \code{sane\_init()} may be called (regardless -of the status value returned by \code{sane\_exit()}. Neglecting to -call this function may result in some resources not being released -properly. -\begin{quote}\index{sane\_exit} -\begin{verbatim} -void sane_exit (void); -\end{verbatim} -\end{quote} - - -\subsection{\code{sane\_get\_devices}} - -This function can be used to query the list of devices that are -available. If the function executes successfully, it stores a pointer -to a \code{NULL} terminated array of pointers to \verb|SANE_Device| -structures in \code{*device\_list}. The returned list is guaranteed -to remain unchanged and valid until (a) another call to this function -is performed or (b) a call to \code{sane\_exit()} is performed. This -function can be called repeatedly to detect when new devices become -available. If argument \code{local\_only} is true, only local devices -are returned (devices directly attached to the machine that SANE is -running on). If it is false, the device list includes all remote -devices that are accessible to the SANE library. -\begin{quote}\index{sane\_get\_devices} -\begin{verbatim} -SANE_Status sane_get_devices (const SANE_Device *** device_list, - SANE_Bool local_only); -\end{verbatim} -\end{quote} - -This function may fail with \code{SANE\_STATUS\_NO\_MEM} if an -insufficient amount of memory is available. - -\begin{quote} - \begin{center} - {\bf Backend Implementation Note} - \end{center} - SANE does not require that this function is called before a - \code{sane\_open()} call is performed. A device name may be - specified explicitly by a user which would make it unnecessary and - undesirable to call this function first. -\end{quote} - - -\subsection{\code{sane\_open}} - -This function is used to establish a connection to a particular -device. The name of the device to be opened is passed in argument -\code{name}. If the call completes successfully, a handle for the -device is returned in \code{*h}. As a special case, specifying a -zero-length string as the device requests opening the first available -device (if there is such a device). -\begin{quote}\index{sane\_open} -\begin{verbatim} -SANE_Status sane_open (SANE_String_Const name, SANE_Handle * h); -\end{verbatim} -\end{quote} - -This function may fail with one of the following status codes. -\begin{quote} -\begin{description} -\item[\code{SANE\_STATUS\_DEVICE\_BUSY}:] The device is currently - busy (in use by somebody else). -\item[\code{SANE\_STATUS\_INVAL}:] The device name is not valid. -\item[\code{SANE\_STATUS\_IO\_ERROR}:] An error occured while - communicating with the device. -\item[\code{SANE\_STATUS\_NO\_MEM}:] An insufficent amount of memory - is available. -\item[\code{SANE\_STATUS\_ACCESS\_DENIED}:] Access to the device has - been denied due to insufficient or invalid authentication. -\end{description} -\end{quote} - - -\subsection{\code{sane\_close}} - -This function terminates the association between the device handle -passed in argument \code{h} and the device it represents. If the -device is presently active, a call to \code{sane\_cancel()} is -performed first. After this function returns, handle \code{h} must -not be used anymore. - -\begin{quote}\index{sane\_close} -\begin{verbatim} -void sane_close (SANE_Handle h); -\end{verbatim} -\end{quote} - -\subsection{\code{sane\_get\_option\_descriptor}} - -This function is used to access option descriptors. The function -returns the option descriptor for option number \code{n} of the device -represented by handle \code{h}. Option number 0 is guaranteed to be a -valid option. Its value is an integer that specifies the number of -options that are available for device handle \code{h} (the count -includes option 0). If $n$ is not a valid option index, the function -returns \code{NULL}. The returned option descriptor is guaranteed to -remain valid (and at the returned address) until the device is closed. - -\begin{quote}\index{sane\_get\_option\_descriptor} -\begin{verbatim} -const SANE_Option_Descriptor * - sane_get_option_descriptor (SANE_Handle h, SANE_Int n); -\end{verbatim} -\end{quote} - -\subsection{\code{sane\_control\_option}}\label{sec:control} - -This function is used to set or inquire the current value of option -number \code{n} of the device represented by handle \code{h}. The -manner in which the option is controlled is specified by parameter -\code{a}. The possible values of this parameter are described in more -detail below. The value of the option is passed through argument -\code{v}. It is a pointer to the memory that holds the option value. -The memory area pointed to by \code{v} must be big enough to hold the -entire option value (determined by member \code{size} in the -corresponding option descriptor). The only exception to this rule is -that when setting the value of a string option, the string pointed to -by argument \code{v} may be shorter since the backend will stop -reading the option value upon encountering the first \code{NUL} -terminator in the string. If argument \code{i} is not \code{NULL}, -the value of \code{*i} will be set to provide details on how well the -request has been met. The meaning of this argument is described in -more detail below. -\begin{quote}\index{sane\_control\_option} -\begin{verbatim} -SANE_Status sane_control_option (SANE_Handle h, SANE_Int n, - SANE_Action a, void *v, - SANE_Int * i); -\end{verbatim} -\end{quote} - -The way the option is affected by a call to this function is -controlled by parameter \code{a} which is a value of type -\code{\defn{SANE\_Action}}. The possible values and their meaning is -described in Table~\ref{tab:actions}. - -\begin{table}[h] - \begin{center} - \leavevmode - \begin{tabular}{|l|r|p{0.5\textwidth}|} -\hline -\multicolumn{1}{|c|}{\bf Symbol} & -\multicolumn{1}{|c|}{\bf Code} & -\multicolumn{1}{|c|}{\bf Description} \\ - -\hline\hline - -\code{\defn{SANE\_ACTION\_GET\_VALUE}} & 0 & Get current option value. \\ - -\code{\defn{SANE\_ACTION\_SET\_VALUE}} & 1 & Set option value. The - option value passed through argument \code{v} may be modified by the - backend if the value cannot be set exactly. \\ - -\code{\defn{SANE\_ACTION\_SET\_AUTO}} & 2 & Turn on automatic mode. Backend - or device will automatically select an appropriate value. This mode - remains effective until overridden by an explicit set value request. - The value of parameter \code{v} is completely ignored in this case and - may be \code{NULL}. \\ - -\hline - \end{tabular} - \caption{Action Values (\code{SANE\_Action})} - \label{tab:actions} - \end{center} -\end{table} - -After setting a value via an action value of -\verb|SANE_ACTION_SET_VALUE|, additional information on how well the -request has been met is returned in \code{*i} (if \code{i} is -non-\code{NULL}). The returned value is a bitset that may contain any -combination of the values described in Table~\ref{tab:info}. -\begin{table}[htbp] - \begin{center} - \leavevmode - \begin{tabular}{|l|r|p{0.5\textwidth}|} -\hline -\multicolumn{1}{|c|}{\bf Symbol} & -\multicolumn{1}{|c|}{\bf Code} & -\multicolumn{1}{|c|}{\bf Description} \\ - -\hline\hline - -\code{\defn{SANE\_INFO\_INEXACT}} & 1 & This value is returned when - setting an option value resulted in a value being selected that does - not exactly match the requested value. For example, if a scanner - can adjust the resolution in increments of 30dpi only, setting the - resolution to 307dpi may result in an actual setting of 300dpi. - When this happens, the bitset returned in \code{*i} has this member - set. In addition, the option value is modified to reflect the - actual (rounded) value that was used by the backend. Note that - inexact values are admissible for strings as well. A backend may - choose to ``round'' a string to the closest matching legal string - for a constrained string value. \\ - - \code{\defn{SANE\_INFO\_RELOAD\_OPTIONS}} & 2 & The setting of an - option may affect the value or availability of one or more {\em - other\/} options. When this happens, the SANE backend sets this - member in \code{*i} to indicate that the application should reload - all options. This member may be set if and only if at least one - option changed. \\ - -\code{\defn{SANE\_INFO\_RELOAD\_PARAMS}} & 4 & The setting of an option may - affect the parameter values (see \code{sane\_get\_parameters()}). - If setting an option affects the parameter values, this member will - be set in \code{*i}. Note that this member may be set even if the - parameters did not actually change. However, it is guaranteed that - the parameters never change without this member being set. \\ - -\hline - \end{tabular} - \caption{Additional Information Returned When Setting an Option} - \label{tab:info} - \end{center} -\end{table} - -This function may fail with one of the following status codes. -\begin{quote} -\begin{description} -\item[\code{SANE\_STATUS\_UNSUPPORTED}:] The operation is not - supported for the specified handle and option number. -\item[\code{SANE\_STATUS\_INVAL}:] The option value is not valid. -\item[\code{SANE\_STATUS\_IO\_ERROR}:] An error occured while - communicating with the device. -\item[\code{SANE\_STATUS\_NO\_MEM}:] An insufficent amount of memory - is available. -\item[\code{SANE\_STATUS\_ACCESS\_DENIED}:] Access to the option has - been denied due to insufficient or invalid authentication. -\end{description} -\end{quote} - - - -\subsection{\code{sane\_get\_parameters}} - -This function is used to obtain the current scan parameters. The -returned parameters are guaranteed to be accurate between the time a -scan has been started (\code{sane\_start()} has been called) and the -completion of that request. Outside of that window, the returned -values are best-effort estimates of what the parameters will be when -\code{sane\_start()} gets invoked. Calling this function before a -scan has actually started allows, for example, to get an estimate of -how big the scanned image will be. The parameters passed to this -function are the handle \code{h} of the device for which the -parameters should be obtained and a pointer \code{p} to a parameter -structure. The parameter structure is described in more detail below. - -\begin{quote}\index{sane\_get\_parameters} -\begin{verbatim} -SANE_Status sane_get_parameters (SANE_Handle h, - SANE_Parameters * p); -\end{verbatim} -\end{quote} - -The scan parameters are returned in a structure of type -\code{\defn{SANE\_Parameters}}. The C declaration of this structure -is given below. -\begin{quote} -\begin{verbatim} -typedef struct - { - SANE_Frame format; - SANE_Bool last_frame; - SANE_Int bytes_per_line; - SANE_Int pixels_per_line; - SANE_Int lines; - SANE_Int depth; - } -SANE_Parameters; -\end{verbatim} -\end{quote} - -Member \code{format} specifies the format of the next frame to be -returned. The possible values for type \code{\defn{SANE\_Frame}} are -described in Table~\ref{tab:frameformat}. The meaning of these -values is described in more detail in Section~\ref{sec:imageformat}. -\begin{table}[htbp] - \begin{center} - \leavevmode - \begin{tabular}{|l|r|l|} -\hline -\multicolumn{1}{|c|}{\bf Symbol} & -\multicolumn{1}{|c|}{\bf Code} & -\multicolumn{1}{|c|}{\bf Description} \\ - -\hline\hline - -\code{\defn{SANE\_FRAME\_GRAY}} & 0 & Band covering human visual range. \\ -\code{\defn{SANE\_FRAME\_RGB}} & 1 & Pixel-interleaved red/green/blue bands. \\ -\code{\defn{SANE\_FRAME\_RED}} & 2 & Red band of a red/green/blue image. \\ -\code{\defn{SANE\_FRAME\_GREEN}} & 3 & Green band of a red/green/blue image. \\ -\code{\defn{SANE\_FRAME\_BLUE}} & 4 & Blue band of a red/green/blue image. \\ - -\hline - \end{tabular} - \caption{Frame Format (\code{SANE\_Frame})} - \label{tab:frameformat} - \end{center} -\end{table} - -Member \code{last\_frame} is set to \code{SANE\_TRUE} if and only if -the frame that is currently being acquired (or the frame that will be -acquired next if there is no current frame) is the last frame of a -multi frame image (e.g., the current frame is the blue component of a -red, green, blue image). - -Member \code{lines} specifies how many scan lines the frame is -comprised of. If this value is -1, the number of lines is not known a -priori and the frontend should call \code{sane\_read()} until it -returns a status of \code{SANE\_STATUS\_EOF}. - -Member \code{bytes\_per\_line} specifies the number of bytes that -comprise one scan line. - -Member \code{depth} specifies the number of bits per sample. - -Member \code{pixels\_per\_line} specifies the number of pixels that -comprise one scan line. - -Assume $B$ is the number of channels in the frame, then the bit depth -$d$ (as given by member \code{depth}) and the number of pixels per -line $n$ (as given by this member \code{pixels\_per\_line}) are -related to $c$, the number of bytes per line (as given by member -\code{bytes\_per\_line}) as follows: -\[ - c >= \left\{ - \begin{array}{ll} - B\cdot \lfloor (n + 7) / 8\rfloor & \mbox{if $d=1$}\\ - B\cdot n \cdot d / 8 & \mbox{if $d>1$} - \end{array} - \right. -\] -Note that the number of bytes per line can be larger than the minimum -value imposed by the right side of this equation. A frontend must be -able to properly cope with such ``padded'' image formats. - - -\subsection{\code{sane\_start}} - -This function initiates aquisition of an image from the device -represented by handle \code{h}. -\begin{quote}\index{sane\_start} -\begin{verbatim} -SANE_Status sane_start (SANE_Handle h); -\end{verbatim} -\end{quote} -This function may fail with one of the following status codes. -\begin{quote} -\begin{description} -\item[\code{SANE\_STATUS\_CANCELLED}:] The operation was cancelled through - a call to \code{sane\_cancel}. -\item[\code{SANE\_STATUS\_DEVICE\_BUSY}:] The device is busy. The - operation should be retried later. -\item[\code{SANE\_STATUS\_JAMMED}:] The document feeder is jammed. -\item[\code{SANE\_STATUS\_NO\_DOCS}:] The document feeder is out of - documents. -\item[\code{SANE\_STATUS\_COVER\_OPEN}:] The scanner cover is open. -\item[\code{SANE\_STATUS\_IO\_ERROR}:] An error occurred while communicating - with the device. -\item[\code{SANE\_STATUS\_NO\_MEM}:] An insufficent amount of memory - is available. -\item[\code{SANE\_STATUS\_INVAL}:] The scan cannot be started with the current - set of options. The frontend should reload the option descriptors, as if - \code{\defn{SANE\_INFO\_RELOAD\_OPTIONS}} had been returned from a call to - \code{sane\_control\_option()}, since the device's capabilities may have - changed. -\end{description} -\end{quote} - - -\subsection{\code{sane\_read}} - -This function is used to read image data from the device represented -by handle \code{h}. Argument \code{buf} is a pointer to a memory area -that is at least \code{maxlen} bytes long. The number of bytes -returned is stored in \code{*len}. A backend must set this to zero -when a status other than \code{SANE\_STA\-TUS\_GOOD} is returned. -When the call succeeds, the number of bytes returned can be anywhere in -the range from 0 to \code{maxlen} bytes. -\begin{quote}\index{sane\_read} -\begin{verbatim} -SANE_Status sane_read (SANE_Handle h, SANE_Byte * buf, - SANE_Int maxlen, SANE_Int * len); -\end{verbatim} -\end{quote} -If this function is called when no data is available, one of two -things may happen, depending on the I/O mode that is in effect for -handle \code{h}. -\begin{enumerate} -\item If the device is in blocking I/O mode (the default mode), the - call blocks until at least one data byte is available (or until some - error occurs). - -\item If the device is in non-blocking I/O mode, the call returns - immediately with status \code{SANE\_STA\-TUS\_GOOD} and with - \code{*len} set to zero. -\end{enumerate} -The I/O mode of handle \code{h} can be set via a call to -\code{sane\_set\_io\_mode()}. - -This function may fail with one of the following status codes. -\begin{quote} -\begin{description} -\item[\code{SANE\_STATUS\_CANCELLED}:] The operation was cancelled through - a call to \code{sane\_cancel}. -\item[\code{SANE\_STATUS\_EOF}:] No more data is available for the - current frame. -\item[\code{SANE\_STATUS\_JAMMED}:] The document feeder is jammed. -\item[\code{SANE\_STATUS\_NO\_DOCS}:] The document feeder is out of - documents. -\item[\code{SANE\_STATUS\_COVER\_OPEN}:] The scanner cover is open. -\item[\code{SANE\_STATUS\_IO\_ERROR}:] An error occurred while communicating - with the device. -\item[\code{SANE\_STATUS\_NO\_MEM}:] An insufficent amount of memory - is available. -\item[\code{SANE\_STATUS\_ACCESS\_DENIED}:] Access to the device has - been denied due to insufficient or invalid authentication. -\end{description} -\end{quote} - - -\subsection{\code{sane\_cancel}} - -This function is used to immediately or as quickly as possible cancel -the currently pending operation of the device represented by handle -\code{h}. -\begin{quote}\index{sane\_cancel} -\begin{verbatim} -void sane_cancel (SANE_Handle h); -\end{verbatim} -\end{quote} -This function can be called at any time (as long as handle \code{h} is -a valid handle) but usually affects long-running operations only (such -as image is acquisition). It is safe to call this function -asynchronously (e.g., from within a signal handler). It is important -to note that completion of this operaton does {\em not\/} imply that -the currently pending operation has been cancelled. It only -guarantees that cancellation has been {\em initiated}. Cancellation -completes only when the cancelled call returns (typically with a -status value of \code{SANE\_STATUS\_CANCELLED}). Since the SANE API -does not require any other operations to be re-entrant, this implies -that a frontend must {\em not\/} call any other operation until the -cancelled operation has returned. - - -\subsection{\code{sane\_set\_io\_mode}} - -This function is used to set the I/O mode of handle \code{h}. The I/O mode -can be either blocking or non-blocking. If argument \code{m} is -\code{SANE\_TRUE}, the mode is set to non-blocking mode, otherwise it's set to -blocking mode. This function can be called only after a call to -\code{sane\_start()} has been performed. -\begin{quote}\index{sane\_set\_io\_mode} -\begin{verbatim} -SANE_Status sane_set_io_mode (SANE_Handle h, SANE_Bool m); -\end{verbatim} -\end{quote} -By default, newly opened handles operate in blocking mode. A backend -may elect not to support non-blocking I/O mode. In such a case the -status value \code{SANE\_STATUS\_UNSUPPORTED} is returned. Blocking -I/O must be supported by all backends, so calling this function with -argument \code{m} set to \code{SANE\_FALSE} is guaranteed to complete -successfully. - -This function may fail with one of the following status codes: -\begin{quote} -\begin{description} -\item[\code{SANE\_STATUS\_INVAL}:] No image acquisition is pending. -\item[\code{SANE\_STATUS\_UNSUPPORTED}:] The backend does not support - the requested I/O mode. -\end{description} -\end{quote} - - -\subsection{\code{sane\_get\_select\_fd}} - -This function is used to obtain a (platform-specific) file-descriptor -for handle \code{h} that is readable if and only if image data is -available (i.e., when a call to \code{sane\_read()} will return at -least one byte of data). If the call completes successfully, the -select file-descriptor is returned in \code{*fd}. -\begin{quote}\index{sane\_get\_select\_fd} -\begin{verbatim} -SANE_Status sane_get_select_fd (SANE_Handle h, SANE_Int *fd); -\end{verbatim} -\end{quote} -This function can be called only after a call to \code{sane\_start()} -has been performed and the returned file-descriptor is guaranteed to -remain valid for the duration of the current image acquisition (i.e., -until \code{sane\_cancel()} or \code{sane\_start()} get called again -or until \code{sane\_read()} returns with status -\code{SANE\_STA\-TUS\_EOF}). Indeed, a backend must guarantee to -close the returned select file descriptor at the point when the next -\code{sane\_read()} call would return \code{SANE\_STA\-TUS\_EOF}. -This is necessary to ensure the application can detect when this -condition occurs without actually having to call \code{sane\_read()}. - -A backend may elect not to support this operation. In such a case, -the function returns with status code -\code{SANE\_STATUS\_UNSUPPORTED}. - -Note that the only operation supported by the returned file-descriptor -is a host operating-system dependent test whether the file-descriptor -is readable (e.g., this test can be implemented using \code{select()} -or \code{poll()} under UNIX). If any other operation is performed on -the file descriptor, the behavior of the backend becomes -unpredictable. Once the file-descriptor signals ``readable'' status, -it will remain in that state until a call to \code{sane\_read()} is -performed. Since many input devices are very slow, support for this -operation is strongly encouraged as it permits an application to do -other work while image acquisition is in progress. - -This function may fail with one of the following status codes: -\begin{quote} -\begin{description} -\item[\code{SANE\_STATUS\_INVAL}:] No image acquisition is pending. -\item[\code{SANE\_STATUS\_UNSUPPORTED}:] The backend does not support - this operation. -\end{description} -\end{quote} - - -\subsection{\code{sane\_strstatus}} - -This function can be used to translate a SANE status code into a -printable string. The returned string is a single line of text that -forms a complete sentence, but without the trailing period -(full-stop). The function is guaranteed to never return \code{NULL}. -The returned pointer is valid at least until the next call to this -function is performed. -\begin{quote}\index{sane\_strstatus} -\begin{verbatim} -const SANE_String_Const sane_strstatus (SANE_Status status); -\end{verbatim} -\end{quote} - -\section{Code Flow}\index{code flow} - -The code flow for the SANE API is illustrated in -Figure~\ref{fig:flow}. Functions \code{sane\_init()} and -\code{sane\_exit()} initialize and exit the backend, respectively. -All other calls must be performed after initialization and before -exiting the backend. - -\begin{figure}[htb] - \begin{center} - \leavevmode - \includegraphics[height=0.5\textheight]{figs/flow} - \caption{Code flow} - \label{fig:flow} - \end{center} -\end{figure} - -Function \code{sane\_get\_devices()} can be called any time after -\code{sane\_init()} has been called. It returns the list of the -devices that are known at the time of the call. This list may change -over time since some devices may be turned on or off or a remote host -may boot or shutdown between different calls. It should be noted that -this operation may be relatively slow since it requires contacting all -configured devices (some of which may be on remote hosts). A frontend -may therefore want to provide the ability for a user to directly -select a desired device without requiring a call to this function. - -Once a device has been chosen, it is opened using a call to -\code{sane\_open()}. Multiple devices can be open at any given time. -A SANE backend must not impose artificial constraints on how many -devices can be open at any given time. - -An opened device can be setup through the corresponding device handle -using functions \code{sane\_get\_opt\-ion\_desc\-riptor()} and -\code{sane\_control\_option()}. While setting up a device, obtaining -option descriptors and setting and reading of option values can be -mixed freely. It is typical for a frontend to read out all available -options at the beginning and then build a dialog (either graphical or -a command-line oriented option list) that allows to control the -available options. It should be noted that the number of options is -fixed for a given handle. However, as options are set, other options -may become active or inactive. Thus, after setting an option, it -maybe necessary to re-read some or all option descriptors. While -setting up the device, it is also admissible to call -\code{sane\_get\_parameters()} to get an estimate of what the image -parameters will look like once image acquisition begins. - -The device handle can be put in blocking or non-blocking mode by a -call to \code{sane\_set\_io\_mode()}. Devices are required to support -blocking mode (which is the default mode), but support for -non-blocking I/O is strongly encouraged for operating systems such as -UNIX. - -After the device is setup properly, image acquisition can be started -by a call to \code{sane\_start()}. The backend calculates the exact -image parameters at this point. So future calls to -\code{sane\_get\_parameters()} will return the exact values, rather -than estimates. Whether the physical image acquisition starts at this -point or during the first call to \code{sane\_read()} is unspecified -by the SANE API. If non-blocking I/O and/or a select-style interface -is desired, the frontend may attempt to call -\code{sane\_set\_io\_mode()} and/or \code{sane\_get\_select\_fd()} at -this point. Either of these functions may fail if the backend does -not support the requested operation. - -Image data is collected by repeatedly calling \code{sane\_read()}. -Eventually, this function will return an end-of-file status -(\code{SANE\_STATUS\_EOF}). This indicates the end of the current -frame. If the frontend expects additional frames (e.g., the -individual channels in of a red/green/blue image or multiple images), -it can call \code{sane\_start()} again. Once all desired frames have -been acquired, function \code{sane\_cancel()} must be called. This -operation can also be called at any other time to cancel a pending -operation. Note that \code{sane\_cancel()} must be called even if the -last read operation returned \code{SANE\_STATUS\_EOF}. - -When done using the device, the handle should be closed by a call to -\code{sane\_close()}. Finally, before exiting the application, -function \code{sane\_exit()} must be called. It is important not to -forget to call this function since otherwise some resources (e.g., -temporary files or locks) may remain unclaimed. - - -\section{Well-Known Options}\index{well-known options} - -While most backend options are completely self-describing, there are a -cases where a user interface might want to special-case the handling -of certain options. For example, the scan area is typically defined -by four options that specify the top-left and bottom-right corners of -the area. With a graphical user interface, it would be tedious to -force the user to type in these four numbers. Instead, most such -interfaces will want to present to the user a preview (low-resolution -scan) of the scanner surface and let the user pick the scan area by -dragging a rectangle into the desired position. For this reason, the -SANE API specifies a small number of option names that have -well-defined meanings. - -\subsection{Option Number Count}\index{option count} - -Option number 0 has an empty string as its name. The value of this -option is of type \code{SANE\_TYPE\_INT} and it specifies the total -number of options available for a given device (the count includes -option number 0). This means that there are two ways of counting the -number of options available: a frontend can either cycle through all -option numbers starting at one until -\code{sane\_get\_option\_descriptor()} returns \code{NULL}, or a -frontend can directly read out the value of option number 0. - -\subsection{Scan Resolution Option}\index{scan resolution}\index{resolution option} - -Option \code{resolution} is used to select the resolution at which an -image should be acquired. The type of this option is either -\code{SANE\_TYPE\_INT} or \code{SANE\_TYPE\_FIXED}. The unit is -\code{SANE\_UNIT\_DPI} (dots/inch). - -This option is not mandatory, but if a backend does support it, it -must implement it in a manner consistent with the above definition. - -\subsection{Preview Mode Option}\index{preview mode} - -The boolean option \code{preview} is used by a frontend to inform the -backend when image acquisition should be optimized for speed, rather -than quality (``preview mode''). When set to \code{SANE\_TRUE}, -preview mode is in effect, when set to \code{SANE\_FALSE} image -acquisition should proceed in normal quality mode. The setting of -this option \emph{must not\/} affect any other option. That is, as -far as the other options are concerned, the preview mode is completely -side effect free. A backend can assume that the frontend will take -care of appropriately setting the scan resolution for preview mode -(through option \code{resolution}). A backend is free to override the -\code{resolution} value with its own choice for preview mode, but it -is advised to leave this choice to the frontend wherever possible. - -This option is not mandatory, but if a backend does support it, it -must implement it in a manner consistent with the above definition. - -\subsection{Scan Area Options}\index{scan area options} - -The four most important well-known options are the ones that define -the scan area. The scan area is defined by two points (x/y coordinate -pairs) that specify the top-left and the bottom-right corners. This -is illustrated in Figure~\ref{fig:area}. Note that the origin of the -coordinate system is at the top-left corner of the scan surface as -seen by the sensor (which typically is a mirror image of the scan -surface seen by the user). For this reason, the top-left corner is -the corner for which the abscissa and ordinate values are -simultaneously the {\em smallest} and the bottom-right corner is the -corner for which the abscissa and ordinate values are simulatenously -the {\em largest}. If this coordinate system is not natural for a -given device, it is the job of the backend to perform the necessary -conversions. -\begin{figure}[tbp] - \begin{center} - \leavevmode - \includegraphics[height=0.3\textheight]{figs/area} - \caption{Scan area options} - \label{fig:area} - \end{center} -\end{figure} - -The names of the four options that define the scan area are given in -the table below: -\begin{center} -\begin{tabular}{ll} -{\bf Name} & {\bf Description} \\ -\code{\defn{tl-x}} & Top-left $x$ coordinate value \\ -\code{\defn{tl-y}} & Top-left $y$ coordinate value \\ -\code{\defn{br-x}} & Bottom-right $x$ coordinate value \\ -\code{\defn{br-y}} & Bottom-right $y$ coordinate value \\ -\end{tabular} -\end{center} -There are several rules that should be followed by front and backends -regarding these options: -\begin{itemize} - -\item Backends must attach a unit of either pixels - (\code{SANE\_UNIT\_PIXEL}) or millimeters (\code{SANE\_UNIT\_MM}) to - these options. The unit of all four options must be identical. - -\item Whenever meaningful, a backend should attach a range or a - word-list constraint to these options. - -\item A frontend can determine the size of the scan surface by first - checking that the options have range constraints associated. If a - range or word-list constraints exist, the frontend can take the - minimum and maximum values of one of the x and y option - range-constraints to determine the scan surface size. - -\item A frontend must work properly with any or all of these options - missing. - -\end{itemize} - -\input{net.tex} - -\chapter{Contact Information}\label{chap:contact} - -The SANE standard is discussed and evolved via a mailing list. -Anybody with email access to the Internet can automatically join and -leave the discussion group by sending mail to the following address. -\begin{quote}\index{mailing list} -\url{sane-devel-request@alioth-lists.debian.net} -\end{quote} -To subscribe, send a mail with the body ``\verb|subscribe sane-devel|'' to the -above address. - -A complete list of commands supported can be obtained by sending a -mail with a subject of ``\code{help}'' to the above address. The -mailing list is archived and available through the SANE home page at -URL: -\begin{quote} -\url{http://www.sane-project.org/} -\end{quote} - -\newpage -\input{sane.ind} - -\end{document} |