src/tiff/man/TIFFOpen.3tiff

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  24 .if n .po 0
  25 .TH TIFFOpen 3TIFF "July 1, 2005" "libtiff"
  26 .SH NAME
  27 TIFFOpen, TIFFFdOpen, TIFFClientOpen \- open a
  28 .SM TIFF
  29 file for reading or writing
  30 .SH SYNOPSIS
  31 .B "#include <tiffio.h>"
  32 .sp
  33 .BI "TIFF* TIFFOpen(const char *" filename ", const char *" mode ")"
  34 .br
  35 .BI "TIFF* TIFFFdOpen(const int " fd ", const char *" filename ", const char *" mode ")"
  36 .sp
  37 .B "typedef tsize_t (*TIFFReadWriteProc)(thandle_t, tdata_t, tsize_t);"
  38 .br
  39 .B "typedef toff_t (*TIFFSeekProc)(thandle_t, toff_t, int);"
  40 .br
  41 .B "typedef int (*TIFFCloseProc)(thandle_t);"
  42 .br
  43 .B "typedef toff_t (*TIFFSizeProc)(thandle_t);"
  44 .br
  45 .B "typedef int (*TIFFMapFileProc)(thandle_t, tdata_t*, toff_t*);"
  46 .br
  47 .B "typedef void (*TIFFUnmapFileProc)(thandle_t, tdata_t, toff_t);"
  48 .sp
  49 .BI "TIFF* TIFFClientOpen(const char *" filename ", const char *" mode ", thandle_t " clientdata ", TIFFReadWriteProc " readproc ", TIFFReadWriteProc " writeproc ", TIFFSeekProc " seekproc ", TIFFCloseProc " closeproc ", TIFFSizeProc " sizeproc ", TIFFMapFileProc " mapproc ", TIFFUnmapFileProc " unmapproc ")"
  50 .SH DESCRIPTION
  51 .IR TIFFOpen
  52 opens a
  53 .SM TIFF
  54 file whose name is
  55 .I filename
  56 and returns a handle to be used in subsequent calls to routines in
  57 .IR libtiff .
  58 If the open operation fails, then zero is returned.
  59 The
  60 .I mode
  61 parameter specifies if the file is to be opened for reading (``r''),
  62 writing (``w''), or appending (``a'') and, optionally, whether
  63 to override certain default aspects of library operation (see below).
  64 When a file is opened for appending, existing data will not
  65 be touched; instead new data will be written as additional subfiles.
  66 If an existing file is opened for writing, all previous data is
  67 overwritten.
  68 .PP
  69 If a file is opened for reading, the first
  70 .SM TIFF
  71 directory in the file is automatically read
  72 (also see
  73 .IR TIFFSetDirectory (3TIFF)
  74 for reading directories other than the first).
  75 If a file is opened for writing or appending, a default directory
  76 is automatically created for writing subsequent data.
  77 This directory has all the default values specified in
  78 .SM TIFF
  79 Revision 6.0:
  80 .IR BitsPerSample =1,
  81 .IR ThreshHolding "=bilevel art scan,"
  82 .IR FillOrder =1
  83 (most significant bit of each data byte is filled first),
  84 .IR Orientation =1
  85 (the 0th row represents the visual top of the image, and the 0th
  86 column represents the visual left hand side),
  87 .IR SamplesPerPixel =1,
  88 .IR RowsPerStrip =infinity,
  89 .IR ResolutionUnit =2
  90 (inches), and
  91 .IR Compression =1
  92 (no compression).
  93 To alter these values, or to define values for additional fields,
  94 .IR TIFFSetField (3TIFF)
  95 must be used.
  96 .PP
  97 .IR TIFFFdOpen
  98 is like
  99 .IR TIFFOpen
 100 except that it opens a
 101 .SM TIFF
 102 file given an open file descriptor
 103 .IR fd .
 104 The file's name and mode must reflect that of the open descriptor.
 105 The object associated with the file descriptor
 106 .BR "must support random access" .
 107 .PP
 108 .IR TIFFClientOpen
 109 is like
 110 .IR TIFFOpen
 111 except that the caller supplies a collection of functions that the
 112 library will use to do \s-1UNIX\s+1-like I/O operations.
 113 The
 114 .I readproc
 115 and
 116 .I writeproc
 117 are called to read and write data at the current file position.
 118 .I seekproc
 119 is called to change the current file position a la
 120 .IR lseek (2).
 121 .I closeproc
 122 is invoked to release any resources associated with an open file.
 123 .I sizeproc
 124 is invoked to obtain the size in bytes of a file.
 125 .I mapproc
 126 and
 127 .I unmapproc
 128 are called to map and unmap a file's contents in memory; c.f.
 129 .IR mmap (2)
 130 and
 131 .IR munmap (2).
 132 The
 133 .I clientdata
 134 parameter is an opaque ``handle'' passed to the client-specified
 135 routines passed as parameters to
 136 .IR TIFFClientOpen .
 137 .SH OPTIONS
 138 The open mode parameter can include the following flags in
 139 addition to the ``r'', ``w'', and ``a'' flags.
 140 Note however that option flags must follow the read-write-append
 141 specification.
 142 .TP
 143 .B l
 144 When creating a new file force information be written with
 145 Little-Endian byte order (but see below).
 146 By default the library will create new files using the native
 147 .SM CPU
 148 byte order.
 149 .TP
 150 .B b
 151 When creating a new file force information be written with
 152 Big-Endian byte order (but see below).
 153 By default the library will create new files using the native
 154 .SM CPU
 155 byte order.
 156 .TP
 157 .B L
 158 Force image data that is read or written to be treated with
 159 bits filled from Least Significant Bit (\s-1LSB\s+1) to
 160 Most Significant Bit (\s-1MSB\s+1).
 161 Note that this is the opposite to the way the library has
 162 worked from its inception.
 163 .TP
 164 .B B
 165 Force image data that is read or written to be treated with
 166 bits filled from Most Significant Bit (\s-1MSB\s+1) to
 167 Least Significant Bit (\s-1LSB\s+1); this is the default.
 168 .TP
 169 .B H
 170 Force image data that is read or written to be treated with
 171 bits filled in the same order as the native
 172 .SM CPU.
 173 .TP
 174 .B M
 175 Enable the use of memory-mapped files for images opened read-only.
 176 If the underlying system does not support memory-mapped files
 177 or if the specific image being opened cannot be memory-mapped
 178 then the library will fallback to using the normal system interface
 179 for reading information.
 180 By default the library will attempt to use memory-mapped files.
 181 .TP
 182 .B m
 183 Disable the use of memory-mapped files.
 184 .TP
 185 .B C
 186 Enable the use of ``strip chopping'' when reading images
 187 that are comprised of a single strip or tile of uncompressed data.
 188 Strip chopping is a mechanism by which the library will automatically
 189 convert the single-strip image to multiple strips,
 190 each of which has about 8 Kilobytes of data.
 191 This facility can be useful in reducing the amount of memory used
 192 to read an image because the library normally reads each strip
 193 in its entirety.
 194 Strip chopping does however alter the apparent contents of the
 195 image because when an image is divided into multiple strips it
 196 looks as though the underlying file contains multiple separate
 197 strips.
 198 Finally, note that default handling of strip chopping is a compile-time
 199 configuration parameter.
 200 The default behaviour, for backwards compatibility, is to enable
 201 strip chopping.
 202 .TP
 203 .B c
 204 Disable the use of strip chopping when reading images.
 205 .TP
 206 .B h
 207 Read TIFF header only, do not load the first image directory. That could be
 208 useful in case of the broken first directory. We can open the file and proceed
 209 to the other directories.
 210 .SH "BYTE ORDER"
 211 The
 212 .SM TIFF
 213 specification (\fBall versions\fP) states that compliant readers
 214 .IR "must be capable of reading images written in either byte order" .
 215 Nonetheless some software that claims to support the reading of
 216 .SM TIFF
 217 images is incapable of reading images in anything but the native
 218 .SM CPU
 219 byte order on which the software was written.
 220 (Especially notorious
 221 are applications written to run on Intel-based machines.)
 222 By default the library will create new files with the native
 223 byte-order of the
 224 .SM CPU
 225 on which the application is run.
 226 This ensures optimal performance and is portable to any application
 227 that conforms to the TIFF specification.
 228 To force the library to use a specific byte-order when creating
 229 a new file the ``b'' and ``l'' option flags may be included in
 230 the call to open a file; for example, ``wb'' or ``wl''.
 231 .SH "RETURN VALUES"
 232 Upon successful completion
 233 .IR TIFFOpen ,
 234 .IR TIFFFdOpen ,
 235 and
 236 .IR TIFFClientOpen
 237 return a
 238 .SM TIFF
 239 pointer.
 240 Otherwise, NULL is returned.
 241 .SH DIAGNOSTICS
 242 All error messages are directed to the
 243 .IR TIFFError (3TIFF)
 244 routine.
 245 Likewise, warning messages are directed to the
 246 .IR TIFFWarning (3TIFF)
 247 routine.
 248 .PP
 249 \fB"%s": Bad mode\fP.
 250 The specified
 251 .I mode
 252 parameter was not one of ``r'' (read), ``w'' (write), or ``a'' (append).
 253 .PP
 254 .BR "%s: Cannot open" .
 255 .IR TIFFOpen ()
 256 was unable to open the specified filename for read/writing.
 257 .PP
 258 .BR "Cannot read TIFF header" .
 259 An error occurred while attempting to read the header information.
 260 .PP
 261 .BR "Error writing TIFF header" .
 262 An error occurred while writing the default header information
 263 for a new file.
 264 .PP
 265 .BR "Not a TIFF file, bad magic number %d (0x%x)" .
 266 The magic number in the header was not (hex)
 267 0x4d4d or (hex) 0x4949.
 268 .PP
 269 .BR "Not a TIFF file, bad version number %d (0x%x)" .
 270 The version field in the header was not 42 (decimal).
 271 .PP
 272 .BR "Cannot append to file that has opposite byte ordering" .
 273 A file with a byte ordering opposite to the native byte
 274 ordering of the current machine was opened for appending (``a'').
 275 This is a limitation of the library.
 276 .SH "SEE ALSO"
 277 .IR libtiff (3TIFF),
 278 .IR TIFFClose (3TIFF)