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Index › Programming Questions & Help › Syntax Questions › How to read transparency/ alpha channel of gif
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How to read transparency/ alpha channel of gif (Read 708 times)
Rapatsk1
How to read transparency/ alpha channel of gif
Apr 22nd, 2009, 5:59am  
Dear all,

I really hope this is a stupid question. I searched the boards, reference, but couldn't find the solution.

Code:

    logo_array[i] = loadImage("logo_"+nr+".gif");
    logo_array[i].loadPixels();

    totalpixels += logo_array[i].pixels.length;

    for (int pix = 0; pix < logo_array[i].pixels.length; pix++) {
	int r = int(red(logo_array[i].pixels[pix]));
	int g = int(green(logo_array[i].pixels[pix]));
	int b = int(blue(logo_array[i].pixels[pix]));

	rgbcount[r][g][b]++;
    }


I have a code running through the pixels of a gif image with transparency and stores pixels by their color. So far, so good. Problem is that I can't find a way to test for transparant pixels. At present, transparant pixels are simply stored as white. I don't know how or where Processing stores the alpha channel of the imported gif.

Please help.
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clankill3r
Re: How to read transparency/ alpha channel of gif
Reply #1 - Apr 22nd, 2009, 6:20am  
maybe you can read it with alpha?

http://processing.org/reference/alpha_.html
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Cedric
Re: How to read transparency/ alpha channel of gif
Reply #2 - Apr 24th, 2009, 1:25am  
As i know, gif defines one color as transparent, this could be every color. not only white. Depends on the software you create it or you j ust define it yourself. Sometimes its a pink too...  So if you get a white back, thats maybe allready your color. Try to creat a gif with a different transparent color and check it...
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Rapatsk1
Re: How to read transparency/ alpha channel of gif
Reply #3 - Apr 24th, 2009, 1:26am  
I strongly believed that didn't work.. but it doed, it seems
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PhiLho 
Re: How to read transparency/ alpha channel of gif
Reply #4 - Apr 24th, 2009, 6:38am  
Cedric wrote on Apr 24th, 2009, 1:25am:
As i know, gif defines one color as transparent
More exactly, one palette entry.
Quote:
Sometimes its a pink too...
Probably magenta... Smiley
Quote:
So if you get a white back, thats maybe allready your color.
Beware, nothing prevents from having, say a transparent white and an opaque one in the same file (two different palette entries).
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Cedric
Re: How to read transparency/ alpha channel of gif
Reply #5 - Apr 24th, 2009, 6:52am  
PINK!  Cheesy
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