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Thread: Image issues

  1. #1
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    Default Image issues

    I've been trying to play around a little with images lately, and I ran into one issue that I've not found any reason for (so I think it's because of a misunderstanding on my part). What I'm trying to do is to draw images that overlap eachother, but parts of the images should be transparent so I can see several images stacked onto eachother. However, no matter what I do I can't make that happen. I make them transparent by doing this (I've preloaded the images before running this code):
        BufferedImage shipimg=new BufferedImage(tempimg.getWidth(null), tempimg.getHeight(null), BufferedImage.TYPE_INT_ARGB);
        Graphics tempg=shipimg.getGraphics();
        tempg.drawImage(tempimg, 0, 0, null);
        for (int x=0;x<shipimg.getWidth(null);x++)
        {
          for (int y=0;y<shipimg.getHeight(null);y++)
          {
            if ((shipimg.getRGB(x, y)&0x00FFFFFF)==0) // If the pixel is black
            {
              System.out.println("Setting "+x+":"+y+" blank.");
              shipimg.setRGB(x, y, 0);
            }
          }
        }
    It prints out the right amounts of "Setting blank" and loops through the right amount of loops, so I doubt there are any problems with the image not being completely loaded, and if I try to read the RGB back it says 0. It still draws the color as black when I use g.drawImage(shipimg, x, y) though (which draws onto another BufferedImage with TYPE_INT_ARGB). Any thoughts?

    Also posted at Image issues


  2. #2
    Administrator copeg's Avatar
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    Default Re: Image issues

    Have you tried playing with the alpha value for a region of consecutive pixels? Right now it looks to be searching for pixels that are white with alpha 0, then setting that pixel to black with alpha 0...with 100% transparency of both the previous and changed pixel I wouldn't expect the picture to change.

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    Default Re: Image issues

    I think you're confusing the mask for the color I'm looking for. I'm masking out the last 24 bits out of the int (i.e. the RGB code) and checking if that RGB code is 0 (i.e. black). I don't care much about the transparency of the original picture (I'm fairly certain the image I'm playing with doesn't contain any alpha-values anyway). Also, none of the pixels become transparent; each new image covers the previous ones, including the black square border.

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    Default Re: Image issues

    I think you're confusing the mask for the color I'm looking for. I'm masking out the last 24 bits out of the int
    Serves me right for posting without drinking my coffee. But I'm still a bit confused...you are setting the alpha to zero on only a few pixels (I presume, how many pixels are being set?). What do you expect to see? Just for kicks, loop through the image and set the alpha to something like 100, then draw onto another image to get an idea of what truly is going on.

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    Default Re: Image issues

    The image is roughly 70-80% black, I'd estimate, so it's more than just a few pixels. I'm also currently drawing one image per x-coordinate (the image is, I believe 64 pixels wide) and randomize on which y-coordinate it's drawn; with a screensize of 640x480, it means I'm drawing 640 images from right to left. The result: I often only see the tip of the ships before the next image covers it.

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    Default Re: Image issues

    Let's see how these images turn out...

    This is how it is right now:

    This is how I want it:

    (and yes, the image in question is taken from another game for testing purposes).

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    Default Re: Image issues

    It can be added that I just changed the Graphics to Graphics2D, but that made no change whatsoever. I'm starting to think that either I've completely misunderstood the alpha-channel, or Java doesn't support it that well (if at all)...

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    Default Re: Image issues

    After a few pointers from the other forum, I found out about and added an AlphaComposite and fiddled a bit more, and might've gotten it to work. I'll mark it as solved in 24 hours if there are no further issues with it.

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