2.2.4.3 ALPHACODEC_BITMAP_STREAM

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The ALPHACODEC_BITMAP_STREAM structure specifies the opacity of each pixel in the encoded bitmap. The number of pixels encoded in the segments field MUST equal the area of the original image when decoded.


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alphaSig

compressed

segments (variable)

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alphaSig (2 bytes): A 16-bit unsigned integer. This field MUST contain the value 16,716 (0x414C).

compressed (2 bytes): A 16-bit unsigned integer. If this field equals 0x0000, the segments field contains the alpha channel values, encoded in raw format, one after the other, in top-left to bottom-right order. If this field is nonzero, the segments field contains one or more CLEARCODEC_ALPHA_RLE_SEGMENT (section 2.2.4.3.1) structures.

segments (variable): An optional variable-length array of bytes or CLEARCODEC_ALPHA_RLE_SEGMENT structures, depending on the value of the compressed field.