From c0b89ac5bfb90835ef01573267020e42d4fe070c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=B6rg=20Frings-F=C3=BCrst?= Date: Sun, 23 Aug 2015 12:17:05 +0200 Subject: Imported Upstream version 1.8.0 --- tiff/html/libtiff.html | 747 ------------------------------------------------- 1 file changed, 747 deletions(-) delete mode 100644 tiff/html/libtiff.html (limited to 'tiff/html/libtiff.html') 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 @@ - - - - Using The TIFF Library - - - - - - - - - - -
-

Using The TIFF Library

-

- libtiff 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. -

-
-
-

- libtiff - 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. -

-

- 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 UNIX - manual pages that accompany this software. -

-

- Michael Still has also written a useful introduction to libtiff for the - IBM DeveloperWorks site available at - http://www.ibm.com/developerworks/linux/library/l-libtiff. -

-

- The following sections are found in this chapter: -

- -
-

How to tell which version you have

-

- The software version can be found by looking at the file named - VERSION - that is located at the top of the source tree; the precise alpha number - is given in the file dist/tiff.alpha. - If you have need to refer to this - specific software, you should identify it as: -

-

- TIFF <version> <alpha> -

-

- where <version> is whatever you get from - "cat VERSION" and <alpha> is - what you get from "cat dist/tiff.alpha". -

-

- Within an application that uses libtiff the TIFFGetVersion - routine will return a pointer to a string that contains software version - information. - The library include file <tiffio.h> contains a C pre-processor - define TIFFLIB_VERSION that can be used to check library - version compatiblity at compile time. -

-
-

Library Datatypes

-

- libtiff defines a portable programming interface through the - use of a set of C type definitions. - These definitions, defined in in the files tiff.h and - tiffio.h, - isolate the libtiff API from the characteristics - of the underlying machine. - To insure portable code and correct operation, applications that use - libtiff should use the typedefs and follow the function - prototypes for the library API. -

-
-

Memory Management

-

- libtiff uses a machine-specific set of routines for managing - dynamically allocated memory. - _TIFFmalloc, _TIFFrealloc, and _TIFFfree - 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 malloc, - realloc, and free routines in the C library.) -

-

- To deal with segmented pointer issues libtiff also provides - _TIFFmemcpy, _TIFFmemset, and _TIFFmemmove - routines that mimic the equivalent ANSI C routines, but that are - intended for use with memory allocated through _TIFFmalloc - and _TIFFrealloc. -

-
-

Error Handling

-

- libtiff 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 TIFFSetErrorHandler. - Likewise warning messages are directed to a single handler routine - that can be specified with a call to TIFFSetWarningHandler -

-
-

Basic File Handling

-

- 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: -

-

- #include "tiffio.h"
- main()
- {
-     TIFF* tif = TIFFOpen("foo.tif", "r");
-     ... do stuff ...
-     TIFFClose(tif);
- } -

-

- The handle returned by TIFFOpen is opaque, 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. -

-

- To create or overwrite a TIFF image the file is also opened, but with - a "w" argument: -

-

- #include "tiffio.h"
- main()
- {
-     TIFF* tif = TIFFOpen("foo.tif", "w");
-     ... do stuff ...
-     TIFFClose(tif);
- } -

-

- If the file already exists it is first truncated to zero length. -

- - - - - -
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.
-

- libtiff buffers much information associated with writing a - valid TIFF image. Consequently, when writing a TIFF image it is necessary - to always call TIFFClose or TIFFFlush to flush any - buffered information to a file. Note that if you call TIFFClose - you do not need to call TIFFFlush. -

-
-

TIFF Directories

-

- TIFF supports the storage of multiple images in a single file. - Each image has an associated data structure termed a directory - 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. -

-

- libtiff 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 TIFFClose or TIFFFlush are called). -

-

- For a file open for reading the TIFFSetDirectory routine can - be used to select an arbitrary directory; directories are referenced by - number with the numbering starting at 0. Otherwise the - TIFFReadDirectory and TIFFWriteDirectory 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: -

-

- #include "tiffio.h"
- main(int argc, char* argv[])
- {
-     TIFF* tif = TIFFOpen(argv[1], "r");
-     if (tif) {
-         int dircount = 0;
-         do {
-             dircount++;
-         } while (TIFFReadDirectory(tif));
-         printf("%d directories in %s\n", dircount, argv[1]);
-         TIFFClose(tif);
-     }
-     exit(0);
- } -

-

- Finally, note that there are several routines for querying the - directory status of an open file: - TIFFCurrentDirectory returns the index of the current - directory and - TIFFLastDirectory returns an indication of whether the - current directory is the last directory in a file. - There is also a routine, TIFFPrintDirectory, that can - be called to print a formatted description of the contents of - the current directory; consult the manual page for complete details. -

-
-

TIFF Tags

-

- Image-related information such as the image width and height, number - of samples, orientation, colorimetric information, etc. - are stored in each image - directory in fields or tags. - 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. -

-

- libtiff 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 elsewhere. -

-

- libtiff provides two interfaces for getting and setting tag - values: TIFFGetField and TIFFSetField. - These routines use a variable argument list-style interface to pass - parameters of different type through a single function interface. - The get interface 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 set interface takes the tag values either by-reference or - by-value. - The TIFF specification defines - default values for some tags. - To get the value of a tag, or its default value if it is undefined, - the TIFFGetFieldDefaulted interface may be used. -

-

- 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. -

-
-

TIFF Compression Schemes

-

- libtiff includes support for a wide variety of - data compression schemes. - In normal operation a compression scheme is automatically used when - the TIFF Compression tag is set, either by opening a file - for reading, or by setting the tag when writing. -

-

- Compression schemes are implemented by software modules termed codecs - 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 TIFFRegisterCODEC routine. - This interface can also be used to override the core-library - implementation for a compression scheme. -

-
-

Byte Order

-

- The TIFF specification says, and has always said, that - a correct TIFF - reader must handle images in big-endian and little-endian byte order. - libtiff 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). -

-
-

Data Placement

-

- 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. - libtiff provides no mechanism for controlling the placement - of data in a file; image data is typically written before directory - information. -

-
-

TIFFRGBAImage Support

-

- libtiff 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. -

-

- 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 TIFFReadRGBAImage can be used: -

-

-

- #include "tiffio.h"
- main(int argc, char* argv[])
- {
-     TIFF* tif = TIFFOpen(argv[1], "r");
-     if (tif) {
-         uint32 w, h;
-         size_t npixels;
-         uint32* raster;
-         
-         TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, &w);
-         TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &h);
-         npixels = w * h;
-         raster = (uint32*) _TIFFmalloc(npixels * sizeof (uint32));
-         if (raster != NULL) {
-             if (TIFFReadRGBAImage(tif, w, h, raster, 0)) {
-                 ...process raster data...
-             }
-             _TIFFfree(raster);
-         }
-         TIFFClose(tif);
-     }
-     exit(0);
- } -

-

- Note above that _TIFFmalloc is used to allocate memory for - the raster passed to TIFFReadRGBAImage; this is important - to insure the ``appropriate type of memory'' is passed on machines - with segmented architectures. -

-

- Alternatively, TIFFReadRGBAImage 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: -

-

- #include "tiffio.h"
- main(int argc, char* argv[])
- {
-     TIFF* tif = TIFFOpen(argv[1], "r");
-     if (tif) {
-         TIFFRGBAImage img;
-         char emsg[1024];
-         
-         if (TIFFRGBAImageBegin(&img, tif, 0, emsg)) {
-             size_t npixels;
-             uint32* raster;
-             
-             npixels = img.width * img.height;
-             raster = (uint32*) _TIFFmalloc(npixels * sizeof (uint32));
-             if (raster != NULL) {
-                 if (TIFFRGBAImageGet(&img, raster, img.width, img.height)) {
-                     ...process raster data...
-                 }
-                 _TIFFfree(raster);
-             }
-             TIFFRGBAImageEnd(&img);
-         } else
-             TIFFError(argv[1], emsg);
-         TIFFClose(tif);
-     }
-     exit(0);
- } -

-

- 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: -

- -

- 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. -

-

- 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. -

-

- 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. -

-

- The TIFF image viewer found in tools/sgigt.c is an example - of an application that makes use of the TIFFRGBAImage - support. -

-
-

Scanline-based Image I/O

-

- The simplest interface provided by libtiff 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 (RowsPerStrip is one). -

-

- Two routines are provided for scanline-based i/o: - TIFFReadScanline - and - TIFFWriteScanline. - For example, to read the contents of a file that - is assumed to be organized in strips, the following might be used: -

-

- #include "tiffio.h"
- main()
- {
-     TIFF* tif = TIFFOpen("myfile.tif", "r");
-     if (tif) {
-         uint32 imagelength;
-         tdata_t buf;
-         uint32 row;
-         
-         TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &imagelength);
-         buf = _TIFFmalloc(TIFFScanlineSize(tif));
-         for (row = 0; row < imagelength; row++)
-             tiffreadscanline(tif, buf, row);
-         _tifffree(buf);
-         tiffclose(tif);
-     }
- } -

-

- TIFFScanlineSize returns the number of bytes in - a decoded scanline, as returned by TIFFReadScanline. - 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: -

-

- #include "tiffio.h"
- main()
- {
-     TIFF* tif = TIFFOpen("myfile.tif", "r");
-     if (tif) {
-         uint32 imagelength;
-         tdata_t buf;
-         uint32 row;
-         
-         TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &imagelength);
-         TIFFGetField(tif, TIFFTAG_PLANARCONFIG, &config);
-         buf = _TIFFmalloc(TIFFScanlineSize(tif));
-         if (config == PLANARCONFIG_CONTIG) {
-             for (row = 0; row < imagelength; row++)
-                 tiffreadscanline(tif, buf, row);
-         } else if (config == planarconfig_separate) {
-             uint16 s, nsamples;
-             
-             tiffgetfield(tif, tifftag_samplesperpixel, &nsamples);
-             for (s = 0; s < nsamples; s++)
-                 for (row = 0; row < imagelength; row++)
-                     tiffreadscanline(tif, buf, row, s);
-         }
-         _tifffree(buf);
-         tiffclose(tif);
-     }
- } -

-

- Beware however that if the following code were used instead to - read data in the case PLANARCONFIG_SEPARATE,... -

-

-             for (row = 0; row < imagelength; row++)
-                 for (s = 0; s < nsamples; s++)
-                     tiffreadscanline(tif, buf, row, s); -

-

- ...then problems would arise if RowsPerStrip 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). -

-
-

Strip-oriented Image I/O

-

- 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. -

-

- A simple example of reading an image by strips is: -

-

- #include "tiffio.h"
- main()
- {
-     TIFF* tif = TIFFOpen("myfile.tif", "r");
-     if (tif) {
-         tdata_t buf;
-         tstrip_t strip;
-         
-         buf = _TIFFmalloc(TIFFStripSize(tif));
-         for (strip = 0; strip < tiffnumberofstrips(tif); strip++)
-             tiffreadencodedstrip(tif, strip, buf, (tsize_t) -1);
-         _tifffree(buf);
-         tiffclose(tif);
-     }
- } -

-

- Notice how a strip size of -1 is used; TIFFReadEncodedStrip - will calculate the appropriate size in this case. -

-

- 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 PLANARCONFIG_SEPARATE - then all the strips of data holding the first sample will be - read, followed by strips for the second sample, etc. -

-

- Finally, note that the last strip of data in an image may have fewer - rows in it than specified by the RowsPerStrip tag. A - reader should not assume that each decoded strip contains a full - set of rows in it. -

-

- The following is an example of how to read raw strips of data from - a file: -

-

- #include "tiffio.h"
- main()
- {
-     TIFF* tif = TIFFOpen("myfile.tif", "r");
-     if (tif) {
-         tdata_t buf;
-         tstrip_t strip;
-         uint32* bc;
-         uint32 stripsize;
-         
-         TIFFGetField(tif, TIFFTAG_STRIPBYTECOUNTS, &bc);
-         stripsize = bc[0];
-         buf = _TIFFmalloc(stripsize);
-         for (strip = 0; strip < tiffnumberofstrips(tif); strip++) {
-             if (bc[strip] > stripsize) {
-                 buf = _TIFFrealloc(buf, bc[strip]);
-                 stripsize = bc[strip];
-             }
-             TIFFReadRawStrip(tif, strip, buf, bc[strip]);
-         }
-         _TIFFfree(buf);
-         TIFFClose(tif);
-     }
- } -

-

- 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. -

-
-

Tile-oriented Image I/O

-

- 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. -

-

- 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. -

-

- 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: -

-

- main()
- {
-     TIFF* tif = TIFFOpen("myfile.tif", "r");
-     if (tif) {
-         uint32 imageWidth, imageLength;
-         uint32 tileWidth, tileLength;
-         uint32 x, y;
-         tdata_t buf;
-         
-         TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, &imageWidth);
-         TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &imageLength);
-         TIFFGetField(tif, TIFFTAG_TILEWIDTH, &tileWidth);
-         TIFFGetField(tif, TIFFTAG_TILELENGTH, &tileLength);
-         buf = _TIFFmalloc(TIFFTileSize(tif));
-         for (y = 0; y < imagelength; y += tilelength)
-             for (x = 0; x < imagewidth; x += tilewidth)
-                 tiffreadtile(tif, buf, x, y, 0);
-         _tifffree(buf);
-         tiffclose(tif);
-     }
- } -

-

- (once again, we assume samples are packed contiguously.) -

-

- Alternatively a direct interface to the low-level data is provided - a la strips. Tiles can be read with - TIFFReadEncodedTile or TIFFReadRawTile, - and written with TIFFWriteEncodedTile or - TIFFWriteRawTile. For example, to read all the tiles in an image: -

-

- #include "tiffio.h"
- main()
- {
-     TIFF* tif = TIFFOpen("myfile.tif", "r");
-     if (tif) {
-         tdata_t buf;
-         ttile_t tile;
-         
-         buf = _TIFFmalloc(TIFFTileSize(tif));
-         for (tile = 0; tile < tiffnumberoftiles(tif); tile++)
-             tiffreadencodedtile(tif, tile, buf, (tsize_t) -1);
-         _tifffree(buf);
-         tiffclose(tif);
-     }
- } -

-
-

Other Stuff

-

- Some other stuff will almost certainly go here... -

-
-

- Last updated: $Date: 2005/12/28 06:53:18 $ -

- - -- cgit v1.2.3