TIFFReadRGBAStrip(3TIFF) TIFFReadRGBAStrip(3TIFF)
NAME
TIFFReadRGBAStrip - read and decode an image strip 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 TIFFReadRGBAStrip(TIFF *tif, uint32_t row, uint32_t *raster)DESCRIPTION
TIFFReadRGBAStrip reads a single strip of a strip-based image into
memory, storing the result in the user supplied RGBA
raster. The
raster is assumed to be an array of width times rowsperstrip 32-bit
entries, where width is the width of the image (TIFFTAG_IMAGEWIDTH)
and rowsperstrip is the maximum lines in a strip
(TIFFTAG_ROWSPERSTRIP).
The
row value should be the row of the first row in the strip (strip
* rowsperstrip, zero based).
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 strip. That is bottom to top
organization. When reading a partial last strip in the file the last
line of the image will begin at the beginning of the buffer.
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.
TIFFReadRGBAStrip 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 strip. The
TIFFReadRGBATile() function does a similar operation for tiled 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),
TIFFReadRGBATile(3TIFF),
libtiff(3TIFF) Libtiff library home page:
http://www.simplesystems.org/libtiff/libtiff December 10, 1998 TIFFReadRGBAStrip(3TIFF)
