intro(3)

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 suit
able for archiving multi-color and monochromatic image
data.

The library supports several compression algorithms, as
indicated by the Compression field, including: no compres sion (1), CCITT 1D Huffman compression (2), CCITT Group 3
Facsimile compression (3), CCITT Group 4 Facsimile com
pression (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 com
pression algorithm (32766) (decompression only), an exper
imental 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 lit
tle- or big-endian byte order-byte swapping is automati
cally 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 sup
port files in which the BitsPerSample, Compression, Min_ SampleValue, or MaxSampleValue fields are defined differ ently on a per-sample basis (in Rev. 6.0 the Compression tag is not defined on a per-sample basis, so this is imma
terial).

DATA TYPES

The library makes extensive use of C typedefs to promote portability. Two sets of typedefs are used, one for com munication with clients of the library and one for inter nal 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 han; dle
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 SamplesPer_ Pixel 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 userspecified data references are passed as opaque handles and
only cast at the lowest layers where their type is pre
sumed.

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 con
taining y,sample TIFFComputeTile tile.3t return tile con
taining 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 han
dler 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 rever
sal 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 im
age data is tiled TIFFIsByteSwapped query.3t return true if im
age 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 di
rectory 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 TIFFRG
BAImage 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 han
dler 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 consid
ered codec-specific tags and the library does not recog nize them except when the Compression tag has been previ ously 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 Sample
Format 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 calcula
tions 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 ExtraSam
ples 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 De
flate 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 calcula
tions 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 calul
cations 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 pseudtags and are used to control various codec-specific func
tions 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 opera
tion 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. Possi
ble values (independent bits that can be combined
by or'ing them together) are: FAXMODE_CLASSIC
(enable old-style format in which the RTC is writ
ten at the end of the last strip), FAXMODE_NORTC
(opposite of FAXMODE_CLASSIC; also called FAX
MODE_CLASSF), FAXMODE_NOEOL (do not write EOL codes
at the start of each row of data), FAX
MODE_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 pseudotag 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 col
ormap 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 redun
dantly 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 JPEGCOLOR
MODE_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: JPEGTA
BLESMODE_QUANT (include quantization tables), and
JPEGTABLESMODE_HUFF (include Huffman encoding
tables). The default value is JPEGTA
BLESMODE_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: PIXARLOG
DATAFMT_8BIT for 8-bit unsigned pixels, PIXARLOG
DATAFMT_8BITABGR for 8-bit unsigned ABGR-ordered
pixels, PIXARLOGDATAFMT_11BITLOG for 11-bit logencoded raw data, PIXARLOGDATAFMT_12BITPICIO for
12-bit PICIO-compatible data, PIXARLOGDATAFMT_16BIT
for 16-bit signed samples, and PIXARLOG
DATAFMT_FLOAT for 32-bit IEEE floating point sam
ples.
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: SGILOG
DATAFMT_FLTXYZ for converting between LogLuv and
32-bit IEEE floating valued XYZ pixels, SGILOG
DATAFMT_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 float
ing 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 rou tine. 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 con tents.

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