summaryrefslogtreecommitdiff
path: root/tiff/html/libtiff.html
diff options
context:
space:
mode:
Diffstat (limited to 'tiff/html/libtiff.html')
-rw-r--r--tiff/html/libtiff.html747
1 files changed, 0 insertions, 747 deletions
diff --git a/tiff/html/libtiff.html b/tiff/html/libtiff.html
deleted file mode 100644
index 6a2c42e..0000000
--- a/tiff/html/libtiff.html
+++ /dev/null
@@ -1,747 +0,0 @@
-<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
-<html lang="en">
-<head>
- <title>Using The TIFF Library</title>
- <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
- <meta http-equiv="content-language" content="en">
- <style type="text/css">
- <!--
- th {text-align: left; vertical-align: top; font-style: italic; font-weight: normal}
- -->
- </style>
-</head>
-<body lang="en" text="#000000" bgcolor="#ffffff" link="#0000ff" alink="#0000ff" vlink="#0000ff">
- <table border="0" cellspacing="0" cellpadding="0">
- <tr>
- <td style="padding-left: 1em; padding-right: 1em"><img src="images/cat.gif" width="113" height="146" alt=""></td>
- <td>
- <h1>Using The TIFF Library</h1>
- <p>
- <tt>libtiff</tt> is a set of C functions (a library) that support
- the manipulation of TIFF image files.
- The library requires an ANSI C compilation environment for building
- and presumes an ANSI C environment for use.
- </p>
- </td>
- </tr>
- </table>
- <br>
- <p>
- <tt>libtiff</tt>
- provides interfaces to image data at several layers of abstraction (and cost).
- At the highest level image data can be read into an 8-bit/sample,
- ABGR pixel raster format without regard for the underlying data organization,
- colorspace, or compression scheme. Below this high-level interface
- the library provides scanline-, strip-, and tile-oriented interfaces that
- return data decompressed but otherwise untransformed. These interfaces
- require that the application first identify the organization of stored
- data and select either a strip-based or tile-based API for manipulating
- data. At the lowest level the library
- provides access to the raw uncompressed strips or tiles,
- returning the data exactly as it appears in the file.
- </p>
- <p>
- The material presented in this chapter is a basic introduction
- to the capabilities of the library; it is not an attempt to describe
- everything a developer needs to know about the library or about TIFF.
- Detailed information on the interfaces to the library are given in
- the <a href="http://www.remotesensing.org/libtiff/man/index.html">UNIX
- manual pages</a> that accompany this software.
- </p>
- <p>
- Michael Still has also written a useful introduction to libtiff for the
- IBM DeveloperWorks site available at
- <a href="http://www.ibm.com/developerworks/linux/library/l-libtiff">http://www.ibm.com/developerworks/linux/library/l-libtiff</a>.
- </p>
- <p>
- The following sections are found in this chapter:
- </p>
- <ul>
- <li><a href="#version">How to tell which version you have</a></li>
- <li><a href="#typedefs">Library Datatypes</a></li>
- <li><a href="#mman">Memory Management</a></li>
- <li><a href="#errors">Error Handling</a></li>
- <li><a href="#fio">Basic File Handling</a></li>
- <li><a href="#dirs">TIFF Directories</a></li>
- <li><a href="#tags">TIFF Tags</a></li>
- <li><a href="#compression">TIFF Compression Schemes</a></li>
- <li><a href="#byteorder">Byte Order</a></li>
- <li><a href="#dataplacement">Data Placement</a></li>
- <li><a href="#tiffrgbaimage">TIFFRGBAImage Support</a></li>
- <li><a href="#scanlines">Scanline-based Image I/O</a></li>
- <li><a href="#strips">Strip-oriented Image I/O</a></li>
- <li><a href="#tiles">Tile-oriented Image I/O</a></li>
- <li><a href="#other">Other Stuff</a></li>
- </ul>
- <hr>
- <h2 id="version">How to tell which version you have</h2>
- <p>
- The software version can be found by looking at the file named
- <tt>VERSION</tt>
- that is located at the top of the source tree; the precise alpha number
- is given in the file <tt>dist/tiff.alpha</tt>.
- If you have need to refer to this
- specific software, you should identify it as:
- </p>
- <p style="margin-left: 40px">
- <tt>TIFF &lt;<i>version</i>&gt; &lt;<i>alpha</i>&gt;</tt>
- </p>
- <p>
- where <tt>&lt;<i>version</i>&gt;</tt> is whatever you get from
- <tt>"cat VERSION"</tt> and <tt>&lt;<i>alpha</i>&gt;</tt> is
- what you get from <tt>"cat dist/tiff.alpha"</tt>.
- </p>
- <p>
- Within an application that uses <tt>libtiff</tt> the <tt>TIFFGetVersion</tt>
- routine will return a pointer to a string that contains software version
- information.
- The library include file <tt>&lt;tiffio.h&gt;</tt> contains a C pre-processor
- define <tt>TIFFLIB_VERSION</tt> that can be used to check library
- version compatiblity at compile time.
- </p>
- <hr>
- <h2 id="typedefs">Library Datatypes</h2>
- <p>
- <tt>libtiff</tt> defines a portable programming interface through the
- use of a set of C type definitions.
- These definitions, defined in in the files <b>tiff.h</b> and
- <b>tiffio.h</b>,
- isolate the <tt>libtiff</tt> API from the characteristics
- of the underlying machine.
- To insure portable code and correct operation, applications that use
- <tt>libtiff</tt> should use the typedefs and follow the function
- prototypes for the library API.
- </p>
- <hr>
- <h2 id="mman">Memory Management</h2>
- <p>
- <tt>libtiff</tt> uses a machine-specific set of routines for managing
- dynamically allocated memory.
- <tt>_TIFFmalloc</tt>, <tt>_TIFFrealloc</tt>, and <tt>_TIFFfree</tt>
- mimic the normal ANSI C routines.
- Any dynamically allocated memory that is to be passed into the library
- should be allocated using these interfaces in order to insure pointer
- compatibility on machines with a segmented architecture.
- (On 32-bit UNIX systems these routines just call the normal <tt>malloc</tt>,
- <tt>realloc</tt>, and <tt>free</tt> routines in the C library.)
- </p>
- <p>
- To deal with segmented pointer issues <tt>libtiff</tt> also provides
- <tt>_TIFFmemcpy</tt>, <tt>_TIFFmemset</tt>, and <tt>_TIFFmemmove</tt>
- routines that mimic the equivalent ANSI C routines, but that are
- intended for use with memory allocated through <tt>_TIFFmalloc</tt>
- and <tt>_TIFFrealloc</tt>.
- </p>
- <hr>
- <h2 id="errors">Error Handling</h2>
- <p>
- <tt>libtiff</tt> handles most errors by returning an invalid/erroneous
- value when returning from a function call.
- Various diagnostic messages may also be generated by the library.
- All error messages are directed to a single global error handler
- routine that can be specified with a call to <tt>TIFFSetErrorHandler</tt>.
- Likewise warning messages are directed to a single handler routine
- that can be specified with a call to <tt>TIFFSetWarningHandler</tt>
- </p>
- <hr>
- <h2 id="fio">Basic File Handling</h2>
- <p>
- The library is modeled after the normal UNIX stdio library.
- For example, to read from an existing TIFF image the
- file must first be opened:
- </p>
- <p style="margin-left: 40px">
- <tt>#include "tiffio.h"<br>
- main()<br>
- {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFF* tif = TIFFOpen("foo.tif", "r");<br>
- &nbsp;&nbsp;&nbsp;&nbsp;... do stuff ...<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFFClose(tif);<br>
- }</tt>
- </p>
- <p>
- The handle returned by <tt>TIFFOpen</tt> is <i>opaque</i>, that is
- the application is not permitted to know about its contents.
- All subsequent library calls for this file must pass the handle
- as an argument.
- </p>
- <p>
- To create or overwrite a TIFF image the file is also opened, but with
- a <tt>"w"</tt> argument:
- <p>
- <p style="margin-left: 40px">
- <tt>#include "tiffio.h"<br>
- main()<br>
- {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFF* tif = TIFFOpen("foo.tif", "w");<br>
- &nbsp;&nbsp;&nbsp;&nbsp;... do stuff ...<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFFClose(tif);<br>
- }</tt>
- </p>
- <p>
- If the file already exists it is first truncated to zero length.
- </p>
- <table>
- <tr>
- <td valign=top><img src="images/warning.gif" width="40" height="40" alt=""></td>
- <td><i>Note that unlike the stdio library TIFF image files may not be
- opened for both reading and writing;
- there is no support for altering the contents of a TIFF file.</i></td>
- </tr>
- </table>
- <p>
- <tt>libtiff</tt> buffers much information associated with writing a
- valid TIFF image. Consequently, when writing a TIFF image it is necessary
- to always call <tt>TIFFClose</tt> or <tt>TIFFFlush</tt> to flush any
- buffered information to a file. Note that if you call <tt>TIFFClose</tt>
- you do not need to call <tt>TIFFFlush</tt>.
- </p>
- <hr>
- <h2 id="dirs">TIFF Directories</h2>
- <p>
- TIFF supports the storage of multiple images in a single file.
- Each image has an associated data structure termed a <i>directory</i>
- that houses all the information about the format and content of the
- image data.
- Images in a file are usually related but they do not need to be; it
- is perfectly alright to store a color image together with a black and
- white image.
- Note however that while images may be related their directories are
- not.
- That is, each directory stands on its own; their is no need to read
- an unrelated directory in order to properly interpret the contents
- of an image.
- </p>
- <p>
- <tt>libtiff</tt> provides several routines for reading and writing
- directories. In normal use there is no need to explicitly
- read or write a directory: the library automatically reads the first
- directory in a file when opened for reading, and directory information
- to be written is automatically accumulated and written when writing
- (assuming <tt>TIFFClose</tt> or <tt>TIFFFlush</tt> are called).
- </p>
- <p>
- For a file open for reading the <tt>TIFFSetDirectory</tt> routine can
- be used to select an arbitrary directory; directories are referenced by
- number with the numbering starting at 0. Otherwise the
- <tt>TIFFReadDirectory</tt> and <tt>TIFFWriteDirectory</tt> routines can
- be used for sequential access to directories.
- For example, to count the number of directories in a file the following
- code might be used:
- </p>
- <p style="margin-left: 40px">
- <tt>#include "tiffio.h"<br>
- main(int argc, char* argv[])<br>
- {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFF* tif = TIFFOpen(argv[1], "r");<br>
- &nbsp;&nbsp;&nbsp;&nbsp;if (tif) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int dircount = 0;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;do {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dircount++;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;} while (TIFFReadDirectory(tif));<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;printf("%d directories in %s\n", dircount, argv[1]);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFClose(tif);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;}<br>
- &nbsp;&nbsp;&nbsp;&nbsp;exit(0);<br>
- }</tt>
- </p>
- <p>
- Finally, note that there are several routines for querying the
- directory status of an open file:
- <tt>TIFFCurrentDirectory</tt> returns the index of the current
- directory and
- <tt>TIFFLastDirectory</tt> returns an indication of whether the
- current directory is the last directory in a file.
- There is also a routine, <tt>TIFFPrintDirectory</tt>, that can
- be called to print a formatted description of the contents of
- the current directory; consult the manual page for complete details.
- </p>
- <hr>
- <h2 id="tags">TIFF Tags</h2>
- <p>
- Image-related information such as the image width and height, number
- of samples, orientation, colorimetric information, etc.
- are stored in each image
- directory in <i>fields</i> or <i>tags</i>.
- Tags are identified by a number that is usually a value registered
- with the Aldus (now Adobe) Corporation.
- Beware however that some vendors write
- TIFF images with tags that are unregistered; in this case interpreting
- their contents is usually a waste of time.
- </p>
- <p>
- <tt>libtiff</tt> reads the contents of a directory all at once
- and converts the on-disk information to an appropriate in-memory
- form. While the TIFF specification permits an arbitrary set of
- tags to be defined and used in a file, the library only understands
- a limited set of tags.
- Any unknown tags that are encountered in a file are ignored.
- There is a mechanism to extend the set of tags the library handles
- without modifying the library itself;
- this is described <a href="addingtags.html">elsewhere</a>.
- </p>
- <p>
- <tt>libtiff</tt> provides two interfaces for getting and setting tag
- values: <tt>TIFFGetField</tt> and <tt>TIFFSetField</tt>.
- These routines use a variable argument list-style interface to pass
- parameters of different type through a single function interface.
- The <i>get interface</i> takes one or more pointers to memory locations
- where the tag values are to be returned and also returns one or
- zero according to whether the requested tag is defined in the directory.
- The <i>set interface</i> takes the tag values either by-reference or
- by-value.
- The TIFF specification defines
- <i>default values</i> for some tags.
- To get the value of a tag, or its default value if it is undefined,
- the <tt>TIFFGetFieldDefaulted</tt> interface may be used.
- </p>
- <p>
- The manual pages for the tag get and set routines specifiy the exact data types
- and calling conventions required for each tag supported by the library.
- </p>
- <hr>
- <h2 id="compression">TIFF Compression Schemes</h2>
- <p>
- <tt>libtiff</tt> includes support for a wide variety of
- data compression schemes.
- In normal operation a compression scheme is automatically used when
- the TIFF <tt>Compression</tt> tag is set, either by opening a file
- for reading, or by setting the tag when writing.
- </p>
- <p>
- Compression schemes are implemented by software modules termed <i>codecs</i>
- that implement decoder and encoder routines that hook into the
- core library i/o support.
- Codecs other than those bundled with the library can be registered
- for use with the <tt>TIFFRegisterCODEC</tt> routine.
- This interface can also be used to override the core-library
- implementation for a compression scheme.
- </p>
- <hr>
- <h2 id="byteorder">Byte Order</h2>
- <p>
- The TIFF specification says, and has always said, that
- <em>a correct TIFF
- reader must handle images in big-endian and little-endian byte order</em>.
- <tt>libtiff</tt> conforms in this respect.
- Consequently there is no means to force a specific
- byte order for the data written to a TIFF image file (data is
- written in the native order of the host CPU unless appending to
- an existing file, in which case it is written in the byte order
- specified in the file).
- </p>
- <hr>
- <h2 id="dataplacement">Data Placement</h2>
- <p>
- The TIFF specification requires that all information except an
- 8-byte header can be placed anywhere in a file.
- In particular, it is perfectly legitimate for directory information
- to be written after the image data itself.
- Consequently TIFF is inherently not suitable for passing through a
- stream-oriented mechanism such as UNIX pipes.
- Software that require that data be organized in a file in a particular
- order (e.g. directory information before image data) does not
- correctly support TIFF.
- <tt>libtiff</tt> provides no mechanism for controlling the placement
- of data in a file; image data is typically written before directory
- information.
- </p>
- <hr>
- <h2 id="tiffrgbaimage">TIFFRGBAImage Support</h2>
- <p>
- <tt>libtiff</tt> provides a high-level interface for reading image
- data from a TIFF file. This interface handles the details of
- data organization and format for a wide variety of TIFF files;
- at least the large majority of those files that one would normally
- encounter. Image data is, by default, returned as ABGR
- pixels packed into 32-bit words (8 bits per sample). Rectangular
- rasters can be read or data can be intercepted at an intermediate
- level and packed into memory in a format more suitable to the
- application.
- The library handles all the details of the format of data stored on
- disk and, in most cases, if any colorspace conversions are required:
- bilevel to RGB, greyscale to RGB, CMYK to RGB, YCbCr to RGB, 16-bit
- samples to 8-bit samples, associated/unassociated alpha, etc.
- </p>
- <p>
- There are two ways to read image data using this interface. If
- all the data is to be stored in memory and manipulated at once,
- then the routine <tt>TIFFReadRGBAImage</tt> can be used:
- </p>
- <p>
- <p style="margin-left: 40px">
- <tt>#include "tiffio.h"<br>
- main(int argc, char* argv[])<br>
- {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFF* tif = TIFFOpen(argv[1], "r");<br>
- &nbsp;&nbsp;&nbsp;&nbsp;if (tif) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32 w, h;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;size_t npixels;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32* raster;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, &amp;w);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &amp;h);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;npixels = w * h;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;raster = (uint32*) _TIFFmalloc(npixels * sizeof (uint32));<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (raster != NULL) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (TIFFReadRGBAImage(tif, w, h, raster, 0)) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;...process raster data...<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;_TIFFfree(raster);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFClose(tif);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;}<br>
- &nbsp;&nbsp;&nbsp;&nbsp;exit(0);<br>
- }</tt>
- </p>
- <p>
- Note above that <tt>_TIFFmalloc</tt> is used to allocate memory for
- the raster passed to <tt>TIFFReadRGBAImage</tt>; this is important
- to insure the ``appropriate type of memory'' is passed on machines
- with segmented architectures.
- </p>
- <p>
- Alternatively, <tt>TIFFReadRGBAImage</tt> can be replaced with a
- more low-level interface that permits an application to have more
- control over this reading procedure. The equivalent to the above
- is:
- </p>
- <p style="margin-left: 40px">
- <tt>#include "tiffio.h"<br>
- main(int argc, char* argv[])<br>
- {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFF* tif = TIFFOpen(argv[1], "r");<br>
- &nbsp;&nbsp;&nbsp;&nbsp;if (tif) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFRGBAImage img;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;char emsg[1024];<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (TIFFRGBAImageBegin(&amp;img, tif, 0, emsg)) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;size_t npixels;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32* raster;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;npixels = img.width * img.height;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;raster = (uint32*) _TIFFmalloc(npixels * sizeof (uint32));<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (raster != NULL) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (TIFFRGBAImageGet(&amp;img, raster, img.width, img.height)) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;...process raster data...<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;_TIFFfree(raster);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFRGBAImageEnd(&amp;img);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;} else<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFError(argv[1], emsg);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFClose(tif);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;}<br>
- &nbsp;&nbsp;&nbsp;&nbsp;exit(0);<br>
- }</tt>
- </p>
- <p>
- However this usage does not take advantage of the more fine-grained
- control that's possible. That is, by using this interface it is
- possible to:
- </p>
- <ul>
- <li>repeatedly fetch (and manipulate) an image without opening
- and closing the file</li>
- <li>interpose a method for packing raster pixel data according to
- application-specific needs (or write the data at all)</li>
- <li>interpose methods that handle TIFF formats that are not already
- handled by the core library</li>
- </ul>
- <p>
- The first item means that, for example, image viewers that want to
- handle multiple files can cache decoding information in order to
- speedup the work required to display a TIFF image.
- </p>
- <p>
- The second item is the main reason for this interface. By interposing
- a "put method" (the routine that is called to pack pixel data in
- the raster) it is possible share the core logic that understands how
- to deal with TIFF while packing the resultant pixels in a format that
- is optimized for the application. This alternate format might be very
- different than the 8-bit per sample ABGR format the library writes by
- default. For example, if the application is going to display the image
- on an 8-bit colormap display the put routine might take the data and
- convert it on-the-fly to the best colormap indices for display.
- </p>
- <p>
- The last item permits an application to extend the library
- without modifying the core code.
- By overriding the code provided an application might add support
- for some esoteric flavor of TIFF that it needs, or it might
- substitute a packing routine that is able to do optimizations
- using application/environment-specific information.
- </p>
- <p>
- The TIFF image viewer found in <b>tools/sgigt.c</b> is an example
- of an application that makes use of the <tt>TIFFRGBAImage</tt>
- support.
- </p>
- <hr>
- <h2 id="scanlines">Scanline-based Image I/O</h2>
- <p>
- The simplest interface provided by <tt>libtiff</tt> is a
- scanline-oriented interface that can be used to read TIFF
- images that have their image data organized in strips
- (trying to use this interface to read data written in tiles
- will produce errors.)
- A scanline is a one pixel high row of image data whose width
- is the width of the image.
- Data is returned packed if the image data is stored with samples
- packed together, or as arrays of separate samples if the data
- is stored with samples separated.
- The major limitation of the scanline-oriented interface, other
- than the need to first identify an existing file as having a
- suitable organization, is that random access to individual
- scanlines can only be provided when data is not stored in a
- compressed format, or when the number of rows in a strip
- of image data is set to one (<tt>RowsPerStrip</tt> is one).
- </p>
- <p>
- Two routines are provided for scanline-based i/o:
- <tt>TIFFReadScanline</tt>
- and
- <tt>TIFFWriteScanline</tt>.
- For example, to read the contents of a file that
- is assumed to be organized in strips, the following might be used:
- </p>
- <p style="margin-left: 40px">
- <tt>#include "tiffio.h"<br>
- main()<br>
- {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFF* tif = TIFFOpen("myfile.tif", "r");<br>
- &nbsp;&nbsp;&nbsp;&nbsp;if (tif) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32 imagelength;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tdata_t buf;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32 row;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &amp;imagelength);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;buf = _TIFFmalloc(TIFFScanlineSize(tif));<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (row = 0; row &lt; imagelength; row++)<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffreadscanline(tif, buf, row);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;_tifffree(buf);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffclose(tif);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;}<br>
- }</tt>
- </p>
- <p>
- <tt>TIFFScanlineSize</tt> returns the number of bytes in
- a decoded scanline, as returned by <tt>TIFFReadScanline</tt>.
- Note however that if the file had been create with samples
- written in separate planes, then the above code would only
- read data that contained the first sample of each pixel;
- to handle either case one might use the following instead:
- </p>
- <p style="margin-left: 40px">
- <tt>#include "tiffio.h"<br>
- main()<br>
- {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFF* tif = TIFFOpen("myfile.tif", "r");<br>
- &nbsp;&nbsp;&nbsp;&nbsp;if (tif) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32 imagelength;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tdata_t buf;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32 row;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &amp;imagelength);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFGetField(tif, TIFFTAG_PLANARCONFIG, &amp;config);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;buf = _TIFFmalloc(TIFFScanlineSize(tif));<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (config == PLANARCONFIG_CONTIG) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (row = 0; row &lt; imagelength; row++)<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffreadscanline(tif, buf, row);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;} else if (config == planarconfig_separate) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint16 s, nsamples;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffgetfield(tif, tifftag_samplesperpixel, &amp;nsamples);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (s = 0; s &lt; nsamples; s++)<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (row = 0; row &lt; imagelength; row++)<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffreadscanline(tif, buf, row, s);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;_tifffree(buf);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffclose(tif);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;}<br>
- }</tt>
- </p>
- <p>
- Beware however that if the following code were used instead to
- read data in the case <tt>PLANARCONFIG_SEPARATE</tt>,...
- </p>
- <p style="margin-left: 40px">
- <tt>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (row = 0; row &lt; imagelength; row++)<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (s = 0; s &lt; nsamples; s++)<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffreadscanline(tif, buf, row, s);</tt>
- </p>
- <p>
- ...then problems would arise if <tt>RowsPerStrip</tt> was not one
- because the order in which scanlines are requested would require
- random access to data within strips (something that is not supported
- by the library when strips are compressed).
- </p>
- <hr>
- <h2 id="strips">Strip-oriented Image I/O</h2>
- <p>
- The strip-oriented interfaces provided by the library provide
- access to entire strips of data. Unlike the scanline-oriented
- calls, data can be read or written compressed or uncompressed.
- Accessing data at a strip (or tile) level is often desirable
- because there are no complications with regard to random access
- to data within strips.
- </p>
- <p>
- A simple example of reading an image by strips is:
- </p>
- <p style="margin-left: 40px">
- <tt>#include "tiffio.h"<br>
- main()<br>
- {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFF* tif = TIFFOpen("myfile.tif", "r");<br>
- &nbsp;&nbsp;&nbsp;&nbsp;if (tif) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tdata_t buf;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tstrip_t strip;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;buf = _TIFFmalloc(TIFFStripSize(tif));<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (strip = 0; strip &lt; tiffnumberofstrips(tif); strip++)<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffreadencodedstrip(tif, strip, buf, (tsize_t) -1);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;_tifffree(buf);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffclose(tif);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;}<br>
- }</tt>
- </p>
- <p>
- Notice how a strip size of <tt>-1</tt> is used; <tt>TIFFReadEncodedStrip</tt>
- will calculate the appropriate size in this case.
- </p>
- <p>
- The above code reads strips in the order in which the
- data is physically stored in the file. If multiple samples
- are present and data is stored with <tt>PLANARCONFIG_SEPARATE</tt>
- then all the strips of data holding the first sample will be
- read, followed by strips for the second sample, etc.
- </p>
- <p>
- Finally, note that the last strip of data in an image may have fewer
- rows in it than specified by the <tt>RowsPerStrip</tt> tag. A
- reader should not assume that each decoded strip contains a full
- set of rows in it.
- </p>
- <p>
- The following is an example of how to read raw strips of data from
- a file:
- </p>
- <p style="margin-left: 40px">
- <tt>#include "tiffio.h"<br>
- main()<br>
- {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFF* tif = TIFFOpen("myfile.tif", "r");<br>
- &nbsp;&nbsp;&nbsp;&nbsp;if (tif) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tdata_t buf;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tstrip_t strip;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32* bc;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32 stripsize;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFGetField(tif, TIFFTAG_STRIPBYTECOUNTS, &amp;bc);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;stripsize = bc[0];<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;buf = _TIFFmalloc(stripsize);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (strip = 0; strip &lt; tiffnumberofstrips(tif); strip++) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (bc[strip] &gt; stripsize) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;buf = _TIFFrealloc(buf, bc[strip]);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;stripsize = bc[strip];<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFReadRawStrip(tif, strip, buf, bc[strip]);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;_TIFFfree(buf);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFClose(tif);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;}<br>
- }</tt>
- </p>
- <p>
- As above the strips are read in the order in which they are
- physically stored in the file; this may be different from the
- logical ordering expected by an application.
- </p>
- <hr>
- <h2 id="tiles">Tile-oriented Image I/O</h2>
- <p>
- Tiles of data may be read and written in a manner similar to strips.
- With this interface, an image is
- broken up into a set of rectangular areas that may have dimensions
- less than the image width and height. All the tiles
- in an image have the same size, and the tile width and length must each
- be a multiple of 16 pixels. Tiles are ordered left-to-right and
- top-to-bottom in an image. As for scanlines, samples can be packed
- contiguously or separately. When separated, all the tiles for a sample
- are colocated in the file. That is, all the tiles for sample 0 appear
- before the tiles for sample 1, etc.
- </p>
- <p>
- Tiles and strips may also be extended in a z dimension to form
- volumes. Data volumes are organized as "slices". That is, all the
- data for a slice is colocated. Volumes whose data is organized in
- tiles can also have a tile depth so that data can be organized in
- cubes.
- </p>
- <p>
- There are actually two interfaces for tiles.
- One interface is similar to scanlines, to read a tiled image,
- code of the following sort might be used:
- </p>
- <p style="margin-left: 40px">
- <tt>main()<br>
- {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFF* tif = TIFFOpen("myfile.tif", "r");<br>
- &nbsp;&nbsp;&nbsp;&nbsp;if (tif) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32 imageWidth, imageLength;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32 tileWidth, tileLength;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;uint32 x, y;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tdata_t buf;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, &amp;imageWidth);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &amp;imageLength);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFGetField(tif, TIFFTAG_TILEWIDTH, &amp;tileWidth);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TIFFGetField(tif, TIFFTAG_TILELENGTH, &amp;tileLength);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;buf = _TIFFmalloc(TIFFTileSize(tif));<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (y = 0; y &lt; imagelength; y += tilelength)<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (x = 0; x &lt; imagewidth; x += tilewidth)<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffreadtile(tif, buf, x, y, 0);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;_tifffree(buf);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffclose(tif);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;}<br>
- }</tt>
- </p>
- <p>
- (once again, we assume samples are packed contiguously.)
- </p>
- <p>
- Alternatively a direct interface to the low-level data is provided
- a la strips. Tiles can be read with
- <tt>TIFFReadEncodedTile</tt> or <tt>TIFFReadRawTile</tt>,
- and written with <tt>TIFFWriteEncodedTile</tt> or
- <tt>TIFFWriteRawTile</tt>. For example, to read all the tiles in an image:
- </p>
- <p style="margin-left: 40px">
- <tt>#include "tiffio.h"<br>
- main()<br>
- {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;TIFF* tif = TIFFOpen("myfile.tif", "r");<br>
- &nbsp;&nbsp;&nbsp;&nbsp;if (tif) {<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tdata_t buf;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ttile_t tile;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;buf = _TIFFmalloc(TIFFTileSize(tif));<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (tile = 0; tile &lt; tiffnumberoftiles(tif); tile++)<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffreadencodedtile(tif, tile, buf, (tsize_t) -1);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;_tifffree(buf);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tiffclose(tif);<br>
- &nbsp;&nbsp;&nbsp;&nbsp;}<br>
- }</tt>
- </p>
- <hr>
- <h2 id="other">Other Stuff</h2>
- <p>
- Some other stuff will almost certainly go here...
- </p>
- <hr>
- <p>
- Last updated: $Date: 2005/12/28 06:53:18 $
- </p>
-</body>
-</html>