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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 as-
       sumed 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 ap-
       propriate zeroed	areas.

       Raster pixels are 8-bit packed red, green,  blue,  alpha	 samples.  The
       macros TIFFGetR,	TIFFGetG, TIFFGetB, and	TIFFGetA should	be used	to ac-
       cess individual samples.	Images without Associated Alpha	matting	infor-
       mation have a constant Alpha of 1.0 (255).

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

NOTES
       Samples must be either 1, 2,  4,	 8,  or	 16  bits.  Colorimetric  sam-
       ples/pixel  must	 be either 1, 3, or 4 (i.e.  SamplesPerPixel minus Ex-
       traSamples).

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

       TIFFReadRGBATile	 is just a wrapper around the more general TIFFRGBAIm-
       age(3TIFF) facilities.  It's main advantage over	the similar  TIFFRead-
       RGBAImage()  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	opera-
       tion for	stripped images.

RETURN VALUES
       1 is returned if	the image was successfully read	and converted.	Other-
       wise, 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	 miss-
       ing  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 mem-
       ory for a table used to convert image samples to	8-bit RGB.

       Missing	required  "Colormap"  tag.  A Palette image did	not have a re-
       quired 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 BitsPer-
       Sample,	SamplesPerPixel, and PhotometricInterpretation)	that TIFFRead-
       RGBAImage can not handle.

       No space	for B&W	mapping	table.	There was insufficient memory to allo-
       cate 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),	 TIFF-
       ReadRGBAStrip(3TIFF), libtiff(3TIFF)

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

libtiff			       December	10, 1998       TIFFReadRGBATile(3TIFF)

NAME | SYNOPSIS | DESCRIPTION | NOTES | RETURN VALUES | DIAGNOSTICS | SEE ALSO

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