PK
libtiff − introduction to libtiff, a library for reading and writing TIFF files
#include <tiffio.h>
cc file.c -ltiff
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).
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.
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
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
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
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
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
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
TIFFVGetFieldDefaulted
TIFFVSetField
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
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
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
BadFaxLines
326
BitsPerSample
258
lots
CellLength
265
parsed but ignored
CellWidth
264
CleanFaxData
327
ColorMap
320
ColorResponseUnit
300
Compression
259
choosing codec
ConsecutiveBadFaxLines
328
Copyright 33432 R/W
DataType
32996
R
obsoleted by SampleFormat tag
DateTime
306
DocumentName
269
DotRange
336
ExtraSamples
338
FaxRecvParams
34908
FaxSubAddress
34909
FaxRecvTime
34910
FillOrder
266
control bit order
FreeByteCounts
289
FreeOffsets
288
GrayResponseCurve
291
GrayResponseUnit
290
Group3Options
292
used by Group 3 codec
Group4Options
293
HostComputer
316
ImageDepth
32997
tile/strip calculations
ImageDescription
270
ImageLength
257
ImageWidth
256
InkNames
333
InkSet
332
JPEGTables
347
used by JPEG codec
Make
271
Matteing
32995
obsoleted by ExtraSamples tag
MaxSampleValue
281
MinSampleValue
280
Model
272
NewSubFileType
254
called SubFileType in spec
NumberOfInks
334
Orientation
274
PageName
285
PageNumber
297
PhotometricInterpretation
262
R/Wused by Group 3 and JPEG codecs
PlanarConfiguration
284
data i/o
Predictor
317
used by LZW and Deflate codecs
PrimaryChromacities
319
ReferenceBlackWhite
532
ResolutionUnit
296
RowsPerStrip
278
SampleFormat
339
SamplesPerPixel
277
SMinSampleValue
340
SMaxSampleValue
341
Software
305
StoNits
37439
StripByteCounts
279
StripOffsets
273
SubFileType
255
called OSubFileType in spec
TargetPrinter
337
Thresholding
263
TileByteCounts
324
TileDepth
32998
TileLength
323
TileOffsets
TileWidth
322
TransferFunction
301
WhitePoint
318
XPosition
286
XResolution
282
YCbCrCoefficients
529
used by TIFFRGBAImage support
YCbCrPositioning
531
tile/strip size calculations
YCbCrSubsampling
530
YPosition
YResolution
283
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.
Codec
TIFFTAG_FAXMODE
G3
general codec operation
TIFFTAG_FAXFILLFUNC
G3/G4
bitmap fill function
TIFFTAG_JPEGQUALITY
JPEG
compression quality control
TIFFTAG_JPEGCOLORMODE
control colorspace conversions
TIFFTAG_JPEGTABLESMODE
control contents of JPEGTables tag
TIFFTAG_ZIPQUALITY
Deflate
R/Wcompression quality level
TIFFTAG_PIXARLOGDATAFMT
PixarLog
R/Wuser data format
TIFFTAG_PIXARLOGQUALITY
TIFFTAG_SGILOGDATAFMT
SGILog
user data format
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.
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.
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.
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.
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.
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.
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.
Control the compression technique used by the PixarLog codec. This value is treated identically to TIFFTAG_ZIPQUALITY; see the above description.
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).
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.
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/
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.