# INTRO

NAME
SYNOPSIS
DESCRIPTION
DATA TYPES
LIST OF ROUTINES
TAG USAGE
PSEUDO TAGS
DIAGNOSTICS
SEE ALSO
BUGS

## 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), 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/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
| 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/Wcompression quality level
| TIFFTAG_PIXARLOGDATAFMT |  | PixarLog | R/Wuser data format
| TIFFTAG_PIXARLOGQUALITY |  | PixarLog | R/Wcompression quality level
| TIFFTAG_SGILOGDATAFMT |  | SGILog | R/W
|  |  |  | user data format

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_IPTCNEWSPHOTO

Tag contains image metadata per the IPTC newsphoto spec: Headline, captioning, credit, etc... Used by most wire services.

TIFFTAG_PHOTOSHOP

Tag contains Photoshop captioning information and metadata. Photoshop uses in parallel and redundantly alongside IPTCNEWSPHOTO information.

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.

TIFFTAG_ZIPQUALITY

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.

TIFFTAG_PIXARLOGDATAFMT

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.

TIFFTAG_PIXARLOGQUALITY

Control the compression technique used by the PixarLog codec. This value is treated identically to TIFFTAG_ZIPQUALITY; see the above description.

TIFFTAG_SGILOGDATAFMT

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.