On Jan 4, 2008 10:58 AM, Anthony Appleyard <[EMAIL PROTECTED]> wrote:
> I have written a program to handle graphics: I am familiar with the
> modes bpp (= bits per pixel) 1 2 4 8 16 24. But when updating that
> program for Windows Vista, I ran into a mode with bpp=32, four bytes
> per pixel. The first three bytes would likely be red, green, blue, as
> in bpp=24 mode; but what is the fourth byte? is it ignored, or
> transparentness, or what?
It's the alpha channel, which is the transparency of the image (so you
have 24 bits of color plus the alpha channel). 32 bit images have been
around since at least the Windows 95 days. Now we even have 48 bit and
higher images (where each pixel's color can be represented as 16 or 32
but floating point numbers per channel (the images you are familiar
still use 8 bits each for color channel). These kinds of images (HDRI)
are used mainly for photography & motion picture work, since film can
display many more colors that what a computer can display. Not
suprisingly, the most popular HDRI format, OpenEXR, was created by
Industrial Light & Magic.
I'd use an imaging library for any of these high-end graphics
(ImageMagick for 8-bit RGB, OpenEXR for HDRI, for example).
-- Brett
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"In the rhythm of music a secret is hidden;
If I were to divulge it, it would overturn the world."
-- Jelaleddin Rumi
