ALPHA

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The _ALPHA function returns the alpha channel level of a color value.


Syntax

result& = _ALPHA(c&[, imageHandle&])


Description

  • 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.
    • Color values that match the clear color set by _CLEARCOLOR have an alpha level of 0 (zero).
    • Color values that don't match the clear color have an alpha level of 255.
  • 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.


See also



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