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 row, uint32 *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.remotesensing.org/libtiff/