TIFFReadRGBAStrip — LibTIFF 4.7.0 documentation

# TIFFReadRGBAStrip

## Synopsis

    #include <tiffio.h>

int TIFFReadRGBAStrip(TIFF *tif, uint32_t row, uint32_t *raster)

int TIFFReadRGBAStripExt(TIFF *tif, uint32_t row, uint32_t *raster, int stop_on_error)

## 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 `ImageWidth` × `RowsPerStrip` 32-bit entries, where `ImageWidth` is the width of the image (`TIFFTAG_IMAGEWIDTH`) and `RowsPerStrip` is the maximum lines in a strip (`TIFFTAG_ROWSPERSTRIP`).

`TIFFReadRGBAStripExt()` provides the paramater stop_on_error. Its behaviour is described at TIFFReadRGBAImage.

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 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` - `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 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 `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\fP`:

> 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)