NAME¶libtiff - introduction to libtiff, a library for reading and writing TIFF files
cc file.c -ltiff
DESCRIPTION¶libtiff is a library for reading and writing data files encoded with the Tag Image File format, Revision 6.0 (or revision 5.0 or revision 4.0). This file format is suitable for archiving multi-color and monochromatic image data.
The library supports several compression algorithms, as indicated by the Compression field, including: no compression (1), CCITT 1D Huffman compression (2), CCITT Group 3 Facsimile compression (3), CCITT Group 4 Facsimile compression (4), Lempel-Ziv & Welch compression (5), baseline JPEG compression (7), word-aligned 1D Huffman compression (32771), and PackBits compression (32773). In addition, several nonstandard compression algorithms are supported: the 4-bit compression algorithm used by the ThunderScan program (32809) (decompression only), NeXT's 2-bit compression algorithm (32766) (decompression only), an experimental LZ-style algorithm known as Deflate (32946), and an experimental CIE LogLuv compression scheme designed for images with high dynamic range (32845 for LogL and 32845 for LogLuv). Directory information may be in either little- or big-endian byte order-byte swapping is automatically done by the library. Data bit ordering may be either Most Significant Bit (MSB) to Least Significant Bit (LSB) or LSB to MSB. Finally, the library does not support files in which the BitsPerSample, Compression, MinSampleValue, or MaxSampleValue fields are defined differently on a per-sample basis (in Rev. 6.0 the Compression tag is not defined on a per-sample basis, so this is immaterial).
DATA TYPES¶The library makes extensive use of C typedefs to promote portability. Two sets of typedefs are used, one for communication with clients of the library and one for internal data structures and parsing of the TIFF format. The following typedefs are exposed to users either through function definitions or through parameters passed through the varargs interfaces.
typedef unsigned short uint16_t; 16-bit unsigned integer typedef unsigned <thing> uint32_t; 32-bit unsigned integer typedef unsigned int ttag_t; directory tag typedef uint16_t tdir_t; directory index typedef uint16_t tsample_t; sample number typedef uint32_t tstrip_t; strip number typedef uint32_t ttile_t; tile number typedef int32_t tsize_t; i/o size in bytes typedef void* tdata_t; image data ref typedef void* thandle_t; client data handle typedef int32_t toff_t; file offset
Note that tstrip_t, ttile_t, and tsize_t are constrained to be no more than 32-bit quantities by 32-bit fields they are stored in in the TIFF image. Likewise tsample_t is limited by the 16-bit field used to store the SamplesPerPixel tag. tdir_t constrains the maximum number of IFDs that may appear in an image and may be an arbitrary size (w/o penalty). ttag_t must be either int, unsigned int, pointer, or double because the library uses a varargs interface and ANSI C restricts the type of the parameter before an ellipsis to be a promoted type. toff_t is defined as int32_t because TIFF file offsets are (unsigned) 32-bit quantities. A signed value is used because some interfaces return -1 on error. Finally, note that user-specified data references are passed as opaque handles and only cast at the lowest layers where their type is presumed.
LIST OF ROUTINES¶The following routines are part of the library. Consult specific manual pages for details on their operation; on most systems doing ``man function-name'' will work.
Name Description TIFFCheckpointDirectory writes the current state of the directory TIFFCheckTile very x,y,z,sample is within image TIFFCIELabToRGBInit initialize CIE L*a*b* 1976 to RGB conversion state TIFFCIELabToXYZ perform CIE L*a*b* 1976 to CIE XYZ conversion TIFFClientOpen open a file for reading or writing TIFFClose close an open file TIFFComputeStrip return strip containing y,sample TIFFComputeTile return tile containing x,y,z,sample TIFFCurrentDirectory return index of current directory TIFFCurrentRow return index of current scanline TIFFCurrentStrip return index of current strip TIFFCurrentTile return index of current tile TIFFDataWidth return the size of TIFF data types TIFFError library error handler TIFFFdOpen open a file for reading or writing TIFFFieldDataType get data type from field information TIFFFieldName get field name from field information TIFFFieldPassCount get whether to pass a value count to Get/SetField TIFFFieldReadCount get number of values to be read from field TIFFFieldTag get tag value from field information TIFFFieldWithName get field information given field name TIFFFieldWithTag get field information given tag TIFFFieldWriteCount get number of values to be written to field TIFFFileName return name of open file TIFFFileno return open file descriptor TIFFFindCODEC find standard codec for the specific scheme TIFFFindField get field information given tag and data type TIFFFlush flush all pending writes TIFFFlushData flush pending data writes TIFFGetBitRevTable return bit reversal table TIFFGetField return tag value in current directory TIFFGetFieldDefaulted return tag value in current directory TIFFGetMode return open file mode TIFFGetVersion return library version string TIFFIsCODECConfigured check, whether we have working codec TIFFIsMSB2LSB return true if image data is being returned with bit 0 as the most significant bit TIFFIsTiled return true if image data is tiled TIFFIsByteSwapped return true if image data is byte-swapped TIFFNumberOfStrips return number of strips in an image TIFFNumberOfTiles return number of tiles in an image TIFFOpen open a file for reading or writing TIFFPrintDirectory print description of the current directory TIFFReadBufferSetup specify i/o buffer for reading TIFFReadDirectory read the next directory TIFFReadEncodedStrip read and decode a strip of data TIFFReadEncodedTile read and decode a tile of data TIFFReadRawStrip read a raw strip of data TIFFReadRawTile read a raw tile of data TIFFReadRGBAImage read an image into a fixed format raster TIFFReadScanline read and decode a row of data TIFFReadTile read and decode a tile of data TIFFRegisterCODEC override standard codec for the specific scheme TIFFReverseBits reverse bits in an array of bytes TIFFRGBAImageBegin setup decoder state for TIFFRGBAImageGet TIFFRGBAImageEnd release TIFFRGBAImage decoder state TIFFRGBAImageGet read and decode an image TIFFRGBAImageOK is image readable by TIFFRGBAImageGet TIFFScanlineSize return size of a scanline TIFFSetDirectory set the current directory TIFFSetSubDirectory set the current directory TIFFSetErrorHandler set error handler function TIFFSetField set a tag's value in the current directory TIFFSetWarningHandler set warning handler function TIFFStripSize returns size of a strip TIFFRawStripSize returns the number of bytes in a raw strip TIFFSwabShort swap bytes of short TIFFSwabLong swap bytes of long TIFFSwabArrayOfShort swap bytes of an array of shorts TIFFSwabArrayOfLong swap bytes of an array of longs TIFFTileRowSize return size of a row in a tile TIFFTileSize return size of a tile TIFFUnRegisterCODEC unregisters the codec TIFFVGetField return tag value in current directory TIFFVGetFieldDefaulted return tag value in current directory TIFFVSetField set a tag's value in the current directory TIFFVStripSize returns the number of bytes in a strip TIFFWarning library warning handler TIFFWriteDirectory write the current directory TIFFWriteEncodedStrip compress and write a strip of data TIFFWriteEncodedTile compress and write a tile of data TIFFWriteRawStrip write a raw strip of data TIFFWriteRawTile write a raw tile of data TIFFWriteScanline write a scanline of data TIFFWriteTile compress and write a tile of data TIFFXYZToRGB perform CIE XYZ to RGB conversion TIFFYCbCrToRGBInit initialize YCbCr to RGB conversion state TIFFYCbCrtoRGB perform YCbCr to RGB conversion Auxiliary functions: _TIFFfree free memory buffer _TIFFmalloc dynamically allocate memory buffer _TIFFmemcmp compare contents of the memory buffers _TIFFmemcpy copy contents of the one buffer to another _TIFFmemset fill memory buffer with a constant byte _TIFFrealloc dynamically reallocate memory buffer
TAG USAGE¶The table below lists the TIFF tags that are recognized and handled by the library. If no use is indicated in the table, then the library reads and writes the tag, but does not use it internally. Note that some tags are meaningful only when a particular compression scheme is being used; e.g. Group3Options is only useful if Compression is set to CCITT Group 3 encoding. Tags of this sort are considered codec-specific tags and the library does not recognize them except when the Compression tag has been previously set to the relevant compression scheme.
Tag Name Value R/W Library Use/Notes
Artist 315 R/W BadFaxLines 326 R/W BitsPerSample 258 R/W lots CellLength 265 parsed but ignored CellWidth 264 parsed but ignored CleanFaxData 327 R/W ColorMap 320 R/W ColorResponseUnit 300 parsed but ignored Compression 259 R/W choosing codec ConsecutiveBadFaxLines 328 R/W Copyright 33432 R/W DataType 32996 R obsoleted by SampleFormat tag DateTime 306 R/W DocumentName 269 R/W DotRange 336 R/W ExtraSamples 338 R/W lots FaxRecvParams 34908 R/W FaxSubAddress 34909 R/W FaxRecvTime 34910 R/W FillOrder 266 R/W control bit order FreeByteCounts 289 parsed but ignored FreeOffsets 288 parsed but ignored GrayResponseCurve 291 parsed but ignored GrayResponseUnit 290 parsed but ignored Group3Options 292 R/W used by Group 3 codec Group4Options 293 R/W HostComputer 316 R/W ImageDepth 32997 R/W tile/strip calculations ImageDescription 270 R/W ImageLength 257 R/W lots ImageWidth 256 R/W lots InkNames 333 R/W InkSet 332 R/W JPEGTables 347 R/W used by JPEG codec Make 271 R/W Matteing 32995 R obsoleted by ExtraSamples tag MaxSampleValue 281 R/W MinSampleValue 280 R/W Model 272 R/W NewSubFileType 254 R/W called SubFileType in spec NumberOfInks 334 R/W Orientation 274 R/W PageName 285 R/W PageNumber 297 R/W PhotometricInterpretation 262 R/W used by Group 3 and JPEG codecs PlanarConfiguration 284 R/W data i/o Predictor 317 R/W used by LZW and Deflate codecs PrimaryChromacities 319 R/W ReferenceBlackWhite 532 R/W ResolutionUnit 296 R/W used by Group 3 codec RowsPerStrip 278 R/W data i/o SampleFormat 339 R/W SamplesPerPixel 277 R/W lots SMinSampleValue 340 R/W SMaxSampleValue 341 R/W Software 305 R/W StoNits 37439 R/W StripByteCounts 279 R/W data i/o StripOffsets 273 R/W data i/o SubFileType 255 R/W called OSubFileType in spec TargetPrinter 337 R/W Thresholding 263 R/W TileByteCounts 324 R/W data i/o TileDepth 32998 R/W tile/strip calculations TileLength 323 R/W data i/o TileOffsets 324 R/W data i/o TileWidth 322 R/W data i/o TransferFunction 301 R/W WhitePoint 318 R/W XPosition 286 R/W XResolution 282 R/W YCbCrCoefficients 529 R/W used by TIFFRGBAImage support YCbCrPositioning 531 R/W tile/strip size calculations YCbCrSubsampling 530 R/W YPosition 286 R/W YResolution 283 R/W used by Group 3 codec
PSEUDO TAGS¶In addition to the normal TIFF tags the library supports a collection of tags whose values lie in a range outside the valid range of TIFF tags. These tags are termed pseudo-tags and are used to control various codec-specific functions within the library. The table below summarizes the defined pseudo-tags.
Tag Name Codec R/W Library Use/Notes
TIFFTAG_FAXMODE G3 R/W general codec operation TIFFTAG_FAXFILLFUNC G3/G4 R/W bitmap fill function TIFFTAG_JPEGQUALITY JPEG R/W compression quality control TIFFTAG_JPEGCOLORMODE JPEG R/W control colorspace conversions TIFFTAG_JPEGTABLESMODE JPEG R/W control contents of JPEGTables tag TIFFTAG_ZIPQUALITY Deflate R/W compression quality level TIFFTAG_PIXARLOGDATAFMT PixarLog R/W user data format TIFFTAG_PIXARLOGQUALITY PixarLog R/W compression quality level TIFFTAG_SGILOGDATAFMT SGILog R/W user data format
- Control the operation of the Group 3 codec. Possible values (independent bits that can be combined by or'ing them together) are: FAXMODE_CLASSIC (enable old-style format in which the RTC is written at the end of the last strip), FAXMODE_NORTC (opposite of FAXMODE_CLASSIC; also called FAXMODE_CLASSF), FAXMODE_NOEOL (do not write EOL codes at the start of each row of data), FAXMODE_BYTEALIGN (align each encoded row to an 8-bit boundary), FAXMODE_WORDALIGN (align each encoded row to an 16-bit boundary), The default value is dependent on the compression scheme; this pseudo-tag is used by the various G3 and G4 codecs to share code.
- Control the function used to convert arrays of black and white runs to packed bit arrays. This hook can be used to image decoded scanlines in multi-bit depth rasters (e.g. for display in colormap mode) or for other purposes. The default value is a pointer to a builtin function that images packed bilevel data.
- Tag contains image metadata per the IPTC newsphoto spec: Headline, captioning, credit, etc... Used by most wire services.
- Tag contains Photoshop captioning information and metadata. Photoshop uses in parallel and redundantly alongside IPTCNEWSPHOTO information.
- Control the compression quality level used in the baseline algorithm. Note that quality levels are in the range 0-100 with a default value of 75.
- Control whether or not conversion is done between RGB and YCbCr colorspaces. Possible values are: JPEGCOLORMODE_RAW (do not convert), and JPEGCOLORMODE_RGB (convert to/from RGB) The default value is JPEGCOLORMODE_RAW.
- Control the information written in the JPEGTables tag. Possible values (independent bits that can be combined by or'ing them together) are: JPEGTABLESMODE_QUANT (include quantization tables), and JPEGTABLESMODE_HUFF (include Huffman encoding tables). The default value is JPEGTABLESMODE_QUANT|JPEGTABLESMODE_HUFF.
- Control the compression technique used by the Deflate codec. Quality levels are in the range 1-9 with larger numbers yielding better compression at the cost of more computation. The default quality level is 6 which yields a good time-space tradeoff.
- Control the format of user data passed in to the PixarLog codec when encoding and passed out from when decoding. Possible values are: PIXARLOGDATAFMT_8BIT for 8-bit unsigned pixels, PIXARLOGDATAFMT_8BITABGR for 8-bit unsigned ABGR-ordered pixels, PIXARLOGDATAFMT_11BITLOG for 11-bit log-encoded raw data, PIXARLOGDATAFMT_12BITPICIO for 12-bit PICIO-compatible data, PIXARLOGDATAFMT_16BIT for 16-bit signed samples, and PIXARLOGDATAFMT_FLOAT for 32-bit IEEE floating point samples.
- Control the compression technique used by the PixarLog codec. This value is treated identically to TIFFTAG_ZIPQUALITY; see the above description.
- Control the format of client data passed in to the SGILog codec when encoding and passed out from when decoding. Possible values are: SGILOGDATAFMT_FLTXYZ for converting between LogLuv and 32-bit IEEE floating valued XYZ pixels, SGILOGDATAFMT_16BITLUV for 16-bit encoded Luv pixels, SGILOGDATAFMT_32BITRAW and SGILOGDATAFMT_24BITRAW for no conversion of data, SGILOGDATAFMT_8BITRGB for returning 8-bit RGB data (valid only when decoding LogLuv-encoded data), SGILOGDATAFMT_FLTY for converting between LogL and 32-bit IEEE floating valued Y pixels, SGILOGDATAFMT_16BITL for 16-bit encoded L pixels, and SGILOGDATAFMT_8BITGRY for returning 8-bit greyscale data (valid only when decoding LogL-encoded data).
DIAGNOSTICS¶All error messages are directed through the TIFFError routine. By default messages are directed to stderr in the form: module: message\n. Warning messages are likewise directed through the TIFFWarning routine.
SEE ALSO¶fax2tiff(1), gif2tiff(1), pal2rgb(1), ppm2tiff(1), rgb2ycbcr(1), ras2tiff(1), raw2tiff(1), sgi2tiff(1), tiff2bw(1), tiffdither(1), tiffdump(1), tiffcp(1), tiffcmp(1), tiffgt(1), tiffinfo(1), tiffmedian(1), tiffsplit(1), tiffsv(1).
Tag Image File Format Specification — Revision 6.0, an Aldus Technical Memorandum.
The Spirit of TIFF Class F, an appendix to the TIFF 5.0 specification prepared by Cygnet Technologies.
Libtiff library home page: http://www.simplesystems.org/libtiff/
BUGS¶The library does not support multi-sample images where some samples have different bits/sample.
The library does not support random access to compressed data that is organized with more than one row per tile or strip.
|November 2, 2005||libtiff|