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

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

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.

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.