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TIFFReadRGBATile(3TIFF) 						  TIFFReadRGBATile(3TIFF)

NAME
       TIFFReadRGBATile - read and decode an image tile into a fixed-format raster

SYNOPSIS
       #include <tiffio.h>

       #define TIFFGetR(abgr)	((abgr) & 0xff)
       #define TIFFGetG(abgr)	(((abgr) >> 8) & 0xff)
       #define TIFFGetB(abgr)	(((abgr) >> 16) & 0xff)
       #define TIFFGetA(abgr)	(((abgr) >> 24) & 0xff)

       int TIFFReadRGBATile(TIFF *tif, uint32 x, uint32 y, uint32 *raster)

DESCRIPTION
       TIFFReadRGBATile reads a single tile of a tile-based image into memory, storing the result
       in the user supplied RGBA raster.  The raster is assumed to be an  array  of  width  times
       length  32-bit  entries, where width is the width of a tile (TIFFTAG_TILEWIDTH) and length
       is the height of a tile (TIFFTAG_TILELENGTH).

       The x and y values are the offsets from the top left corner to the top left corner of  the
       tile to be read.  They must be an exact multiple of the tile width and length.

       Note  that  the	raster is assume to be organized such that the pixel at location (x,y) is
       raster[y*width+x]; with the raster origin in the lower-left hand corner of the tile.  That
       is  bottom to top organization.	Edge tiles which partly fall off the image will be filled
       out with appropriate zeroed areas.

       Raster pixels are 8-bit packed red, green,  blue,  alpha  samples.  The	macros	TIFFGetR,
       TIFFGetG, TIFFGetB, and TIFFGetA should be used to access individual samples. Images with-
       out Associated Alpha matting information have a constant Alpha of 1.0(255).

       See the TIFFRGBAImage(3TIFF) page for more details on how various  image  types	are  con-
       verted to RGBA values.

NOTES
       Samples	must  be either 1, 2, 4, 8, or 16 bits. Colorimetric samples/pixel must be either
       1, 3, or 4 (i.e.  SamplesPerPixel minus ExtraSamples).

       Palette image colormaps that appear to be incorrectly written as 8-bit values are automat-
       ically scaled to 16-bits.

       TIFFReadRGBATile  is  just  a wrapper around the more general TIFFRGBAImage(3TIFF) facili-
       ties.  It's main advantage over the similar TIFFReadRGBAImage() function is that for large
       images  a  single  buffer capable of holding the whole image doesn't need to be allocated,
       only enough for one tile.  The TIFFReadRGBAStrip() function does a similar  operation  for
       stripped images.

RETURN VALUES
       1  is returned if the image was successfully read and converted.  Otherwise, 0 is returned
       if an error was encountered.

DIAGNOSTICS
       All error messages are directed to the TIFFError(3TIFF) routine.

       Sorry, can not handle %d-bit pictures.  The image had BitsPerSample other than 1, 2, 4, 8,
       or 16.

       Sorry,  can  not handle %d-channel images.  The image had SamplesPerPixel other than 1, 3,
       or 4.

       Missing needed "PhotometricInterpretation" tag.	 The  image  did  not  have  a	tag  that
       describes how to display the data.

       No  "PhotometricInterpretation"	tag,  assuming	RGB.   The  image  was missing a tag that
       describes how to display it, but because it has 3 or 4 samples/pixel, it is assumed to  be
       RGB.

       No  "PhotometricInterpretation"	tag,  assuming min-is-black.  The image was missing a tag
       that describes how to display it, but because it has 1 sample/pixel, it is assumed to be a
       grayscale or bilevel image.

       No space for photometric conversion table.  There was insufficient memory for a table used
       to convert image samples to 8-bit RGB.

       Missing required "Colormap" tag.  A Palette image did not have a required Colormap tag.

       No space for tile buffer.  There was insufficient memory to allocate an i/o buffer.

       No space for strip buffer.  There was insufficient memory to allocate an i/o buffer.

       Can not handle format.  The image has a format (combination of BitsPerSample,  SamplesPer-
       Pixel, and PhotometricInterpretation) that TIFFReadRGBAImage can not handle.

       No space for B&W mapping table.	There was insufficient memory to allocate a table used to
       map grayscale data to RGB.

       No space for Palette mapping table.  There was insufficient memory  to  allocate  a  table
       used to map data to 8-bit RGB.

SEE ALSO
       TIFFOpen(3TIFF), TIFFRGBAImage(3TIFF), TIFFReadRGBAImage(3TIFF), TIFFReadRGBAStrip(3TIFF),
       libtiff(3TIFF)

       Libtiff library home page: http://www.remotesensing.org/libtiff/

libtiff 				December 10, 1998		  TIFFReadRGBATile(3TIFF)
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