Transparent GIF files 
Author Message
 Transparent GIF files

Hi,

  I've put together a GIF viewer but, for the life of me I can't seem to get
any comprehensive background information to display a file with a transparent
background!

  Byte 12 of the header is supposed to be the color index for the 'background'
color and then, later on, if a bit is set the image is transparent. The
background index number is ALWAYS zero but, in a couple of test files only a
few pixels were indexed to zero and that was NOT the background index number.

  Any help you could offer would be appreciated!

TIA,

  ____    _    ____      ____  _____
 |  _ \  / \  / ___) __ | ___)(_   _)
 | |_)  / _ \ \____\/  \|  _)   | |
 |____//_/ \_\(____/\__/|_|     |_|

     www.basicguru.com/schullian



Thu, 30 Nov 2000 03:00:00 GMT  
 Transparent GIF files



Quote:

>Hi,

>  I've put together a GIF viewer but, for the life of me I can't seem to get
>any comprehensive background information to display a file with a transparent
>background!

>  Byte 12 of the header is supposed to be the color index for the 'background'
>color and then, later on, if a bit is set the image is transparent. The
>background index number is ALWAYS zero but, in a couple of test files only a
>few pixels were indexed to zero and that was NOT the background index number.

The background index is *not* always zero... and the background color
is *not* always the transparent color...

The GIF specs. give the Graphic Control Extension as...
[Extension Introducer]
[Graphic Control Label]
[Block Size]
[Packed Fields]
[Delay Time]
[Transparent Color Index]
[Block Terminator]

The [Transparent Color Index] is the transparent color for the image
it corresponds to...

Quote:
>  Any help you could offer would be appreciated!

>TIA,

>  ____    _    ____      ____  _____
> |  _ \  / \  / ___) __ | ___)(_   _)
> | |_)  / _ \ \____\/  \|  _)   | |
> |____//_/ \_\(____/\__/|_|     |_|

>     www.basicguru.com/schullian

--
Samiel

http://www.fastlane.net/~samiel


Mon, 04 Dec 2000 03:00:00 GMT  
 
 [ 2 post ] 

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