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;	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

TIFFCheckpointDirectory writedir.3t		writes the current state of the directory
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
TIFFDataWidth	width.3t	return the size of TIFF data types
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
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 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_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 contaings 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.

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.