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diff --git a/tiff/html/libtiff.html b/tiff/html/libtiff.html deleted file mode 100755 index 16355ad..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 <<i>version</i>> <<i>alpha</i>></tt> - </p> - <p> - where <tt><<i>version</i>></tt> is whatever you get from - <tt>"cat VERSION"</tt> and <tt><<i>alpha</i>></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><tiffio.h></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> - TIFF* tif = TIFFOpen("foo.tif", "r");<br> - ... do stuff ...<br> - 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> - TIFF* tif = TIFFOpen("foo.tif", "w");<br> - ... do stuff ...<br> - 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> - TIFF* tif = TIFFOpen(argv[1], "r");<br> - if (tif) {<br> - int dircount = 0;<br> - do {<br> - dircount++;<br> - } while (TIFFReadDirectory(tif));<br> - printf("%d directories in %s\n", dircount, argv[1]);<br> - TIFFClose(tif);<br> - }<br> - 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> - TIFF* tif = TIFFOpen(argv[1], "r");<br> - if (tif) {<br> - uint32 w, h;<br> - size_t npixels;<br> - uint32* raster;<br> - <br> - TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, &w);<br> - TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &h);<br> - npixels = w * h;<br> - raster = (uint32*) _TIFFmalloc(npixels * sizeof (uint32));<br> - if (raster != NULL) {<br> - if (TIFFReadRGBAImage(tif, w, h, raster, 0)) {<br> - ...process raster data...<br> - }<br> - _TIFFfree(raster);<br> - }<br> - TIFFClose(tif);<br> - }<br> - 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> - TIFF* tif = TIFFOpen(argv[1], "r");<br> - if (tif) {<br> - TIFFRGBAImage img;<br> - char emsg[1024];<br> - <br> - if (TIFFRGBAImageBegin(&img, tif, 0, emsg)) {<br> - size_t npixels;<br> - uint32* raster;<br> - <br> - npixels = img.width * img.height;<br> - raster = (uint32*) _TIFFmalloc(npixels * sizeof (uint32));<br> - if (raster != NULL) {<br> - if (TIFFRGBAImageGet(&img, raster, img.width, img.height)) {<br> - ...process raster data...<br> - }<br> - _TIFFfree(raster);<br> - }<br> - TIFFRGBAImageEnd(&img);<br> - } else<br> - TIFFError(argv[1], emsg);<br> - TIFFClose(tif);<br> - }<br> - 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> - TIFF* tif = TIFFOpen("myfile.tif", "r");<br> - if (tif) {<br> - uint32 imagelength;<br> - tdata_t buf;<br> - uint32 row;<br> - <br> - TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &imagelength);<br> - buf = _TIFFmalloc(TIFFScanlineSize(tif));<br> - for (row = 0; row < imagelength; row++)<br> - tiffreadscanline(tif, buf, row);<br> - _tifffree(buf);<br> - tiffclose(tif);<br> - }<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> - TIFF* tif = TIFFOpen("myfile.tif", "r");<br> - if (tif) {<br> - uint32 imagelength;<br> - tdata_t buf;<br> - uint32 row;<br> - <br> - TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &imagelength);<br> - TIFFGetField(tif, TIFFTAG_PLANARCONFIG, &config);<br> - buf = _TIFFmalloc(TIFFScanlineSize(tif));<br> - if (config == PLANARCONFIG_CONTIG) {<br> - for (row = 0; row < imagelength; row++)<br> - tiffreadscanline(tif, buf, row);<br> - } else if (config == planarconfig_separate) {<br> - uint16 s, nsamples;<br> - <br> - tiffgetfield(tif, tifftag_samplesperpixel, &nsamples);<br> - for (s = 0; s < nsamples; s++)<br> - for (row = 0; row < imagelength; row++)<br> - tiffreadscanline(tif, buf, row, s);<br> - }<br> - _tifffree(buf);<br> - tiffclose(tif);<br> - }<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> for (row = 0; row < imagelength; row++)<br> - for (s = 0; s < nsamples; s++)<br> - 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> - TIFF* tif = TIFFOpen("myfile.tif", "r");<br> - if (tif) {<br> - tdata_t buf;<br> - tstrip_t strip;<br> - <br> - buf = _TIFFmalloc(TIFFStripSize(tif));<br> - for (strip = 0; strip < tiffnumberofstrips(tif); strip++)<br> - tiffreadencodedstrip(tif, strip, buf, (tsize_t) -1);<br> - _tifffree(buf);<br> - tiffclose(tif);<br> - }<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> - TIFF* tif = TIFFOpen("myfile.tif", "r");<br> - if (tif) {<br> - tdata_t buf;<br> - tstrip_t strip;<br> - uint32* bc;<br> - uint32 stripsize;<br> - <br> - TIFFGetField(tif, TIFFTAG_STRIPBYTECOUNTS, &bc);<br> - stripsize = bc[0];<br> - buf = _TIFFmalloc(stripsize);<br> - for (strip = 0; strip < tiffnumberofstrips(tif); strip++) {<br> - if (bc[strip] > stripsize) {<br> - buf = _TIFFrealloc(buf, bc[strip]);<br> - stripsize = bc[strip];<br> - }<br> - TIFFReadRawStrip(tif, strip, buf, bc[strip]);<br> - }<br> - _TIFFfree(buf);<br> - TIFFClose(tif);<br> - }<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> - TIFF* tif = TIFFOpen("myfile.tif", "r");<br> - if (tif) {<br> - uint32 imageWidth, imageLength;<br> - uint32 tileWidth, tileLength;<br> - uint32 x, y;<br> - tdata_t buf;<br> - <br> - TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, &imageWidth);<br> - TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &imageLength);<br> - TIFFGetField(tif, TIFFTAG_TILEWIDTH, &tileWidth);<br> - TIFFGetField(tif, TIFFTAG_TILELENGTH, &tileLength);<br> - buf = _TIFFmalloc(TIFFTileSize(tif));<br> - for (y = 0; y < imagelength; y += tilelength)<br> - for (x = 0; x < imagewidth; x += tilewidth)<br> - tiffreadtile(tif, buf, x, y, 0);<br> - _tifffree(buf);<br> - tiffclose(tif);<br> - }<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> - TIFF* tif = TIFFOpen("myfile.tif", "r");<br> - if (tif) {<br> - tdata_t buf;<br> - ttile_t tile;<br> - <br> - buf = _TIFFmalloc(TIFFTileSize(tif));<br> - for (tile = 0; tile < tiffnumberoftiles(tif); tile++)<br> - tiffreadencodedtile(tif, tile, buf, (tsize_t) -1);<br> - _tifffree(buf);<br> - tiffclose(tif);<br> - }<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> |