INTRO(3T)

NAME

libtiff - introduction to libtiff, a library for reading and writing TIFF files

SYNOPSIS

#include <tiffio.h>
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), and an experimental LZ-style algorithm known as Deflate (32946). 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;      16-bit unsigned integer
typedef unsigned <thing> uint32;      32-bit unsigned integer
typedef unsigned int ttag_t;      directory tag
typedef uint16 tdir_t;      directory index
typedef uint16 tsample_t;      sample number
typedef uint32 tstrip_t;      strip number
typedef uint32 ttile_t;      tile number
typedef int32 tsize_t;      i/o size in bytes
typedef void* tdata_t;      image data ref
typedef void* thandle_t;      client data handle
typedef int32 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 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. The manual page names listed below are for systems where the full function names can not be encoded in the filesystem; on most systems doing ``man function-name'' will work.

     Name                   Appears on Page  Description
     TIFFCheckTile          tile.3t          very x,y,z,sample is within image
     TIFFClientOpen         open.3t          open a file for reading or writing
     TIFFClose              close.3t         close an open file
     TIFFComputeStrip       strip.3t         return strip containing y,sample
     TIFFComputeTile        tile.3t          return tile containing x,y,z,sample
     TIFFCurrentDirectory   query.3t         return index of current directory
     TIFFCurrentRow         query.3t         return index of current scanline
     TIFFCurrentStrip       query.3t         return index of current strip
     TIFFCurrentTile        query.3t         return index of current tile
     TIFFError              error.3t         library error handler
     TIFFFdOpen             open.3t          open a file for reading or writing
     TIFFFileName           query.3t         return name of open file
     TIFFFileno             query.3t         return open file descriptor
     TIFFFlush              flush.3t         flush all pending writes
     TIFFFlushData          flush.3t         flush pending data writes
     TIFFGetBitRevTable     swab.3t          return bit reversal table
     TIFFGetField           getfield.3t      return tag value in current directory
     TIFFGetFieldDefaulted  getfield.3t      return tag value in current directory
     TIFFGetMode            query.3t         return open file mode
     TIFFGetVersion         query.3t         return library version string
     TIFFIsTiled            query.3t         return true if image data is tiled
     TIFFIsByteSwapped      query.3t         return true if image data is byte-swapped
     TIFFNumberOfStrips     strip.3t         return number of strips in an image
     TIFFNumberOfTiles      tile.3t          return number of tiles in an image
     TIFFOpen               open.3t          open a file for reading or writing
     TIFFPrintDirectory     print.3t         print description of the current directory
     TIFFReadBufferSetup    rdbuf.3t         specify i/o buffer for reading
     TIFFReadDirectory      readdir.3t       read the next directory
     TIFFReadEncodedStrip   rdestrip.3t      read and decode a strip of data
     TIFFReadEncodedTile    rdetile.3t       read and decode a tile of data
     TIFFReadRawStrip       rdrstrip.3t      read a raw strip of data
     TIFFReadRawTile        rdrtile.3t       read a raw tile of data
     TIFFReadRGBAImage      rdimage.3t       read an image into a fixed format raster
     TIFFReadScanline       readline.3t      read and decode a row of data
     TIFFReadTile           readtile.3t      read and decode a tile of data
     TIFFReverseBits        swab.3t          reverse bits in an array of bytes
     TIFFRGBAImageBegin     rgbaimage.3t     setup decoder state for TIFFRGBAImageGet
     TIFFRGBAImageEnd       rgbaimage.3t     release TIFFRGBAImage decoder state
     TIFFRGBAImageGet       rgbaimage.3t     read and decode an image
     TIFFRGBAImageOK        rgbaimage.3t     is image readable by TIFFRGBAImageGet
     TIFFScanlineSize       size.3t          return size of a scanline
     TIFFSetDirectory       setdir.3t        set the current directory
     TIFFSetSubDirectory    setdir.3t        set the current directory
     TIFFSetErrorHandler    error.3t         set error handler function
     TIFFSetField           setfield.3t      set a tag's value in the current directory
     TIFFSetWarningHandler  error.3t         set warning handler function
     TIFFStripSize          size.3t          return size of a strip
     TIFFSwabShort          swab.3t          swap bytes of short
     TIFFSwabLong           swab.3t          swap bytes of long
     TIFFSwabArrayOfShort   swab.3t          swap bytes of an array of shorts
     TIFFSwabArrayOfLong    swab.3t          swap bytes of an array of longs
     TIFFTileRowSize        size.3t          return size of a row in a tile
     TIFFTileSize           size.3t          return size of a tile
     TIFFVGetField          getfield.3t      return tag value in current directory
     TIFFVGetFieldDefaulted getfield.3t      return tag value in current directory
     TIFFVSetField          setfield.3t      set a tag's value in the current directory
     TIFFWarning            warning.3t       library warning handler
     TIFFWriteDirectory     writedir.3t      write the current directory
     TIFFWriteEncodedStrip  wrestrip.3t      compress and write a strip of data
     TIFFWriteEncodedTile   wretile.3t       compress and write a tile of data
     TIFFWriteRawStrip      wrrstrip.3t      write a raw strip of data
     TIFFWriteRawTile       wrrtile.3t       write a raw tile of data
     TIFFWriteScanline      writeline.3t     write a scanline of data
     TIFFWriteTile          wrrtile.3t       compress and write a tile of data

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
     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/Wused 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
     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 calulcations
     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 pseud-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_FAXMODE
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.

TIFFTAG_FAXFILLFUNC
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.

TIFFTAG_JPEGQUALITY
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.

TIFFTAG_JPEGCOLORMODE
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.

TIFFTAG_JPEGTABLESMODE
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.

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), 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.

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. The library discards unknown tags. The library should do more validity checking of a directory's contents.