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Thread: Messing with alpha

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    Default Messing with alpha

    I am using something a kin to this:

            for (int w=0;w<bi.getWidth();w++) {          
            for (int h=0;h<bi.getHeight();h++) {
                int color = bi.getRGB(w, h);
                color = color << 5;
       	    bi.setRGB(w, h, color);
     
            }
     
        }

    I am using a solid green image so

     11111111000000001111111100000000

    I just wanted to see how it looked so bumped it over 5 places (obviously changing the color). To my surprise, there was no added transparency. I mean moving it to the left would make the alpha:

    11100000

    I am thinking that setRGB() doesn't effect alpha. Is this accurate?


    *UPDATE*

    Tested it and in fact setRGB has no effect on the alpha bits. So now the question is how can I gain access to them. Any help is appreciated; personally I am going to look into the writable Raster API. Perhaps, I can also use a modified awt to access directly OS data.
    Last edited by KAJLogic; May 24th, 2014 at 03:11 PM.


  2. #2
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    Default Re: Messing with alpha

    I recommend posting an SSCCE that reproduces the problem - the code posted is not clear as to what 'bi' is (BufferedImage?) and how it was constrcted (if a BufferedImage - does it have alpha, how are the bits arranged (rgba, argb, rgb, etc...).?)

  3. The Following User Says Thank You to copeg For This Useful Post:

    KAJLogic (May 26th, 2014)

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    Default Re: Messing with alpha

    I wrote an article on this a few years ago. Might be worth a read.

    http://www.javaprogrammingforums.com...-tutorial.html

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    Default Re: Messing with alpha

    Yes I ended up using a WritableRaster to change the alpha. It is my understanding that BufferedImage alone has no ability to change alpha, only the RGB values. And, yes copeg bi was bufferedImage, I apologize for being vague. Sometimes though I feel like I give too much information. I think the above question could have been truncated to; "does bufferedImage's method setRGB have the ability to change alpha." Then it would have been a simple no answer. In any case I will mark this resolved.

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