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|
TIFFReadRGBAStrip
=================
Synopsis
--------
.. highlight:: c
::
#include <tiffio.h>
.. c:function:: int TIFFReadRGBAStrip(TIFF* tif, uint32_t row, uint32_t* raster)
Description
-----------
:c:func:`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
(:c:macro:`TIFFTAG_IMAGEWIDTH`) and ``RowsPerStrip`` is the maximum lines
in a strip (:c:macro:`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
:c:macro:`TIFFGetR`, :c:macro:`TIFFGetG`, :c:macro:`TIFFGetB`, and
:c:macro:`TIFFGetA` should be used to access individual samples. Images
without Associated Alpha matting information have a constant Alpha of 1.0
(255).
See the :doc:`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.
:c:func:`TIFFReadRGBAStrip` is just a wrapper around the more general
:doc:`TIFFRGBAImage` facilities. It's main advantage over the similar
:c:func:`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 :c:func:`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 :c:func:`TIFFError` 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 :c:func:`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
--------
:doc:`TIFFOpen` (3tiff),
:doc:`TIFFRGBAImage` (3tiff),
:doc:`TIFFReadRGBAImage` (3tiff),
:doc:`TIFFReadRGBATile` (3tiff),
:doc:`libtiff` (3tiff)
|
