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+ TIFFReadRGBATile − read and decode an image tile +into a fixed-format raster + |
+
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+ #include <tiffio.h> + |
+
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+
+ #define TIFFGetR(abgr) + |
++ | + |
+
+ ((abgr) & 0xff) + |
+
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+
+ #define TIFFGetG(abgr) + |
++ | + |
+
+ (((abgr) >> 8) & 0xff) + |
+
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+
+ #define TIFFGetB(abgr) + |
++ | + |
+
+ (((abgr) >> 16) & 0xff) + |
+
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+
+ #define TIFFGetA(abgr) + |
++ | + |
+
+ (((abgr) >> 24) & 0xff) + |
+
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+ int TIFFReadRGBATile(TIFF *tif, +uint32 x, uint32 y, uint32 +*raster) + |
+
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+ TIFFReadRGBATile reads a single tile of a +tile-based image into memory, storing the result in the user +supplied RGBA raster. The raster is assumed to be an +array of width times length 32-bit entries, where width is +the width of a tile (TIFFTAG_TILEWIDTH) and length is the +height of a tile (TIFFTAG_TILELENGTH). + +The x and y values are the offsets from the +top left corner to the top left corner of the tile to be +read. They must be an exact multiple of the tile width and +length. + +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 +tile. That is bottom to top organization. Edge tiles which +partly fall off the image will be filled out with +appropriate zeroed areas. + +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. + |
+
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+ 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. + +TIFFReadRGBATile 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 tile. The TIFFReadRGBAStrip() +function does a similar operation for stripped images. + |
+
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+ 1 is returned if the image was successfully read and +converted. Otherwise, 0 is returned if an error was +encountered. + |
+
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+ 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. + |
+
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+ TIFFOpen(3TIFF), TIFFRGBAImage(3TIFF), +TIFFReadRGBAImage(3TIFF), +TIFFReadRGBAStrip(3TIFF), libtiff(3TIFF) + +Libtiff library home page: +http://www.remotesensing.org/libtiff/ + |
+