TIFFReadRGBAImage
TIFFReadRGBAImage(3T) TIFFReadRGBAImage(3T)
NAME
TIFFReadRGBAImage - read and decode an image 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 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, stor-
ing 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 orga-
nized 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 col-
orimetry information present in the directory.
The paramater stopOnError specifies how to act if an error is encoun-
tered while reading the image. If stopOnError is non-zero, then an
error will terminate the operation; otherwise 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. Colorimetric sam-
ples/pixel must be either 1, 3, or 4 (i.e. SamplesPerPixel 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 general TIFFRGBAIm-
age(3T) facilities.
RETURN VALUES
1 is returned if the image was successfully read and converted. Other-
wise, 0 is returned if an error was encountered and stopOnError is
zero.
DIAGNOSTICS
All error messages are directed to the TIFFError(3T) 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
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 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.
BUGS
Orientations other than bottom-left, or top-left are not handled cor-
rectly.
SEE ALSO
libtiff(3T), TIFFOpen(3T), TIFFRGBAImage(3T), TIFFReadRGBAStrip(3T),
TIFFReadRGBATile(3T)
February 14, 1992 TIFFReadRGBAImage(3T)
