src/tiff/man/TIFFReadRGBATile.3tiff

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