Table of Contents

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 )DescriptionTIFFReadRGBATile
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(3) page for more
details on how various image types are converted to RGBA values. 
NotesSamples
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(3) 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 Values1 is returned if the image was successfully read and converted.
Otherwise, 0 is returned if an error was encountered. DiagnosticsAll error
messages are directed to the TIFFError(3) 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 Alsolibtiff(3), TIFFOpen(3), TIFFRGBAImage(3), TIFFReadRGBAImage(3),
TIFFReadRGBAStrip(3)