TIFFReadRGBATile¶
Synopsis¶
#include <tiffio.h>
-
int TIFFReadRGBATile(TIFF *tif, uint32_t x, uint32_t y, uint32_t *raster)¶
-
int TIFFReadRGBATileExt(TIFF *tif, uint32_t col, uint32_t row, uint32_t *raster, int stop_on_error)¶
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 TileWidth
× TileLength
32-bit entries, where TileWidth
is the width of a tile
(TIFFTAG_TILEWIDTH
) and TileLength
is the height of a
tile (TIFFTAG_TILELENGTH
).
TIFFReadRGBATileExt()
provides the parameter stop_on_error.
Its behaviour is described at TIFFReadRGBAImage.
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 page for more details on how various image types are converted to RGBA values.
Notes¶
TIFFReadRGBATile()
is just a wrapper around the more general
TIFFRGBAImage 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.
For general notes see TIFFRGBImage notes.
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 TIFFErrorExtR()
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
, andPhotometricInterpretation
) thatTIFFReadRGBAImage()
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)