"Kevin Myers" <[EMAIL PROTECTED]> writes:
> Does the value of the alpha channel provide the transparency level
> for each pixel, and if so, then what does that have to do with
Your guess is right, or rather, almost right. The alpha channel
actually provides the opacity levels for each pixel since usually a
fully transparent pixel has an alpha value of 0 while a fully opaque
pixel has an alpha value of 1.0 (or 100% or 255 or 65535 or ...,
depending on how the data is actually stored).
> Also, how is level of transparency actually applied in order compute
> the final display values for a pixel when a semi-transparent pixel
> is overlaid onto an underlying non-transparent pixel?
The formula is basically
dest = (1 - alpha) * dest + alpha * src
We assume that the alpha value runs from 0.0 to 1.0 here.
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