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Revision as of 02:26, 31 January 2010 by
The _ALPHA function returns the alpha channel level of a color value.
result& = _ALPHA(c&[, imageHandle&])
- If imageHandle& is omitted, it is assumed to be the current write page.
- If the image specified by imageHandle& uses a palette, c& is the palette index of the color value used to retrieve the alpha level.
- If the image specified by imageHandle& does not use a palette, c& is the color value used to retrieve the alpha level.
- If imageHandle& is an invalid handle, an illegal function call error is thrown.
- _RED32, _GREEN32, _BLUE32 & _ALPHA32 are all equivalent to _RED, _GREEN, _BLUE & _ALPHA but they are highly optimized and only accept a 32-bit color (B8:G8:R8:A8). Using these in your code (as appose to dividing then ANDing 32-bit color values manually) makes your code easy to read too.