Problem with TIFF alpha channel
Problem with TIFF alpha channel
- Subject: Problem with TIFF alpha channel
- From: Jeff Disher <email@hidden>
- Date: Mon, 8 Oct 2001 20:36:02 -0700 (PDT)
Hello,
I am working on a program that reads in a 24-bit RGB
TIFF image from a file and adds an alpha channel to
make it into a 32-bit RGBA TIFF image which it then
displays on the screen.
So far, whenever I am adding the alpha channel to 100%
opacity (255 unsigned integer) the image displays
perfectly opaque and with the proper RGB data
expressed just as if it were a 24-bit RGB image.
However, if the alpha channel of any pixel is set less
than 100% the pixel appears as if it were black (but
the alpha value seems to be properly expressed). I
tried logging one of the pixels and its values are
what they are supposed to be. I also put the image in
the dock and it did properly act semi-transparent. I
also am confused by the way that an outline appears
around where the image should be.
Can anyone shed some light on this for me because I am
completely confused by this behavior?
Thanks,
Jeff.
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