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
       without 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
       converted 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
       automatically scaled to 16-bits.

       TIFFReadRGBATile   is   just  a  wrapper  around  the  more  general  TIFFRGBAImage(3TIFF)
       facilities.  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,
       SamplesPerPixel, 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.simplesystems.org/libtiff/