src/tiff/man/TIFFReadRGBATile.3tiff

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  25 .if n .po 0
  26 .TH TIFFReadRGBATile 3TIFF "December 10, 1998" "libtiff"
  27 .SH NAME
  28 TIFFReadRGBATile \- read and decode an image tile into a fixed-format raster
  29 .SH SYNOPSIS
  30 .B "#include <tiffio.h>"
  31 .sp
  32 .B "#define TIFFGetR(abgr)      ((abgr) & 0xff)"
  33 .br
  34 .B "#define TIFFGetG(abgr)      (((abgr) >> 8) & 0xff)"
  35 .br
  36 .B "#define TIFFGetB(abgr)      (((abgr) >> 16) & 0xff)"
  37 .br
  38 .B "#define TIFFGetA(abgr)      (((abgr) >> 24) & 0xff)"
  39 .sp
  40 .BI "int TIFFReadRGBATile(TIFF *" tif ", uint32 " x ", uint32 " y ", uint32 *" raster ")"
  41 .SH DESCRIPTION
  42 .IR TIFFReadRGBATile
  43 reads a single tile of a tile-based image into memory, storing the result in
  44 the user supplied RGBA
  45 .IR raster .
  46 The raster is assumed to be an array of width times length 32-bit entries,
  47 where width is the width of a tile (TIFFTAG_TILEWIDTH) and length is the
  48 height of a tile (TIFFTAG_TILELENGTH).
  49
  50 .PP
  51 The
  52 .IR x
  53 and
  54 .IR y
  55 values are the offsets from the top left corner to the top left corner of the
  56 tile to be read.  They must be an exact multiple of the tile width and length.
  57
  58 .PP
  59 Note that the raster is assume to be organized such that the pixel at location
  60 (\fIx\fP,\fIy\fP) is \fIraster\fP[\fIy\fP*\fIwidth\fP+\fIx\fP]; with the
  61 raster origin in the
  62 .I lower-left hand corner
  63 of the tile. That is bottom to top organization.  Edge tiles which partly fall
  64 off the image will be filled out with appropriate zeroed areas.
  65
  66 .PP
  67 Raster pixels are 8-bit packed red, green, blue, alpha samples. The macros
  68 .IR TIFFGetR ,
  69 .IR TIFFGetG ,
  70 .IR TIFFGetB ,
  71 and
  72 .I TIFFGetA
  73 should be used to access individual samples. Images without Associated Alpha
  74 matting information have a constant Alpha of 1.0 (255).
  75 .PP
  76 See the
  77 .IR TIFFRGBAImage (3TIFF)
  78 page for more details on how various image types are converted to RGBA values.
  79 .SH NOTES
  80 Samples must be either 1, 2, 4, 8, or 16 bits. Colorimetric samples/pixel must
  81 be either 1, 3, or 4 (i.e.
  82 .I SamplesPerPixel
  83 minus
  84 .IR ExtraSamples ).
  85 .PP
  86 Palette image colormaps that appear to be incorrectly written as 8-bit values
  87 are automatically scaled to 16-bits.
  88 .PP
  89 .I TIFFReadRGBATile
  90 is just a wrapper around the more general
  91 .IR TIFFRGBAImage (3TIFF)
  92 facilities.  It's main advantage over the similar
  93 .IR TIFFReadRGBAImage()
  94 function is that for large images a single buffer capable of holding the whole
  95 image doesn't need to be allocated, only enough for one tile.  The
  96 .IR TIFFReadRGBAStrip()
  97 function does a similar operation for stripped images.
  98 .SH "RETURN VALUES"
  99 1 is returned if the image was successfully read and converted.
 100 Otherwise, 0 is returned if an error was encountered.
 101 .SH DIAGNOSTICS
 102 All error messages are directed to the
 103 .IR TIFFError (3TIFF)
 104 routine.
 105 .PP
 106 .BR "Sorry, can not handle %d-bit pictures" .
 107 The image had
 108 .I BitsPerSample
 109 other than 1, 2, 4, 8, or 16.
 110 .PP
 111 .BR "Sorry, can not handle %d-channel images" .
 112 The image had
 113 .I SamplesPerPixel
 114 other than 1, 3, or 4.
 115 .PP
 116 \fBMissing needed "PhotometricInterpretation" tag\fP.
 117 The image did not have a tag that describes how to display the data.
 118 .PP
 119 \fBNo "PhotometricInterpretation" tag, assuming RGB\fP.
 120 The image was missing a tag that describes how to display it, but because it
 121 has 3 or 4 samples/pixel, it is assumed to be
 122 .SM RGB.
 123 .PP
 124 \fBNo "PhotometricInterpretation" tag, assuming min-is-black\fP.
 125 The image was missing a tag that describes how to display it,
 126 but because it has 1 sample/pixel, it is assumed to be a grayscale
 127 or bilevel image.
 128 .PP
 129 .BR "No space for photometric conversion table" .
 130 There was insufficient memory for a table used to convert
 131 image samples to 8-bit
 132 .SM RGB.
 133 .PP
 134 \fBMissing required "Colormap" tag\fP.
 135 A Palette image did not have a required
 136 .I Colormap
 137 tag.
 138 .PP
 139 .BR "No space for tile buffer" .
 140 There was insufficient memory to allocate an i/o buffer.
 141 .PP
 142 .BR "No space for strip buffer" .
 143 There was insufficient memory to allocate an i/o buffer.
 144 .PP
 145 .BR "Can not handle format" .
 146 The image has a format (combination of
 147 .IR BitsPerSample ,
 148 .IR SamplesPerPixel ,
 149 and
 150 .IR PhotometricInterpretation )
 151 that
 152 .I TIFFReadRGBAImage
 153 can not handle.
 154 .PP
 155 .BR "No space for B&W mapping table" .
 156 There was insufficient memory to allocate a table used to map
 157 grayscale data to
 158 .SM RGB.
 159 .PP
 160 .BR "No space for Palette mapping table" .
 161 There was insufficient memory to allocate a table used to map data to 8-bit
 162 .SM RGB.
 163 .SH "SEE ALSO"
 164 .BR TIFFOpen (3TIFF),
 165 .BR TIFFRGBAImage (3TIFF),
 166 .BR TIFFReadRGBAImage (3TIFF),
 167 .BR TIFFReadRGBAStrip (3TIFF),
 168 .BR libtiff (3TIFF)
 169 .PP
 170 Libtiff library home page:
 171 .BR http://www.remotesensing.org/libtiff/