tiffreadrgbaimage(3)
NAME
TIFFReadRGBAImage - read and decode an image into a fixedformat 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 TIFFReadRGBAImage(TIFF* tif, u_long width, u_long height, u_long* raster, int stopOnError)
DESCRIPTION
TIFFReadRGBAImage reads a strip- or tile-based image into
memory, storing the result in the user supplied raster.
The raster is assumed to be an array of width times height
32-bit entries, where width must be less than or equal to
the width of the image (height may be any non-zero size).
If the raster dimensions are smaller than the image, the
image data is cropped to the raster bounds. If the raster
height is greater than that of the image, then the image
data are placed in the lower part of the raster. (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.)
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).
TIFFReadRGBAImage converts non-8-bit images by scaling
sample values. Palette, grayscale, bilevel, CMYK, and
YCbCr images are converted to RGB transparently. Raster
pixels are returned uncorrected by any colorimetry infor
mation present in the directory.
The paramater stopOnError specifies how to act if an error
is encountered while reading the image. If stopOnError is
non-zero, then an error will terminate the operation; oth
erwise TIFFReadRGBAImage will continue processing data
until all the possible data in the image have been
requested.
NOTES
In C++ the stopOnError parameter defaults to 0.
Samples must be either 1, 2, 4, 8, or 16 bits. Colorimet
ric samples/pixel must be either 1, 3, or 4 (i.e. Sam_
plesPerPixel minus ExtraSamples).
Palettte image colormaps that appear to be incorrectly
written as 8-bit values are automatically scaled to
16-bits.
TIFFReadRGBAImage is just a wrapper around the more gen
eral TIFFRGBAImage(3) facilities.
RETURN VALUES
1 is returned if the image was successfully read and con
verted. Otherwise, 0 is returned if an error was
encountered and stopOnError is zero.
DIAGNOSTICS
All error messages are directed to the TIFFError(3) rou
tine.
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 sam
ples 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 (combina tion of BitsPerSample, SamplesPerPixel, and PhotometricIn_ terpretation) 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 insuffi
cient memory to allocate a table used to map data to 8-bit
RGB.
BUGS
Orientations other than bottom-left, or top-left are not
handled correctly.
SEE ALSO
- libtiff(3), TIFFOpen(3), TIFFRGBAImage(3), TIFFReadRGBAS_
trip(3), TIFFReadRGBATile(3)