Java: Merging 2 images is not working

Question

I'm trying to read 2 image files, then merge image2 on top of image1, but the code below does not seem to work. After saving, I only see image1 as original. Both images are PNG.

String url= uploadPath + filename;
BufferedImage im = ImageIO.read(url);
String url2= "image2.png";
BufferedImage im2 = ImageIO.read(url);
Graphics2D g = im.createGraphics();
g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.8f));
g.drawImage(im2, im.getWidth()/2, im.getHeight()/2, null);
g.dispose();
ImageIO.write(im, "png", new File( url ));

What did I miss here? Thanks

For better help sooner, post an [SSCCE](http://sscce.org/). – Andrew Thompson Feb 02 '13 at 03:02 — Andrew Thompson, Feb 02 '13 at 03:02
There's no exception been thrown? – MadProgrammer Feb 02 '13 at 05:17 — MadProgrammer, Feb 02 '13 at 05:17

score 3 · Answer 1 · answered Feb 02 '13 at 03:10

3

Your problem is im2 is exactly the same as im:

BufferedImage im = ImageIO.read(url);
BufferedImage im2 = ImageIO.read(url);

I guess it is a typo: it should be url2 rather than url to be read as im2, Am I right?

BufferedImage im2 = ImageIO.read(url2);

answered Feb 02 '13 at 03:10

shuangwhywhy

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Hi, yes typo, but still does not work. It still saves image1 as original. – jeet Feb 02 '13 at 03:22
@jeet And I agree to MadProgrammer's suggestion of the possibility that you draw `im2` out of `im`'s bounds. BTW, how large are your two images? – shuangwhywhy Feb 02 '13 at 10:06
If you merge two identical images, which exactly other output could you expect? – Audrius Meškauskas Feb 02 '13 at 13:30

score 3 · Accepted Answer · answered Feb 02 '13 at 06:47

I had no issues getting it to work.

enter image description here

I did find this line...

g.drawImage(im2, im.getWidth()/2, im.getHeight()/2, null);

Of a little concern. It MIGHT be possible to render the image outside of the background image, if the image sizes are just right. You should be using coordinates that are relative to the master image...

public class MergeImages {

    public static void main(String[] args) {
        File inner = new File("Inner.png");
        File outter = new File("Outter.png");

        try {

            BufferedImage biInner = ImageIO.read(inner);
            BufferedImage biOutter = ImageIO.read(outter);

            System.out.println(biInner);
            System.out.println(biOutter);

            Graphics2D g = biOutter.createGraphics();
            g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.8f));
            int x = (biOutter.getWidth() - biInner.getWidth()) / 2;
            int y = (biOutter.getHeight() - biInner.getHeight()) / 2;
            System.out.println(x + "x" + y);
            g.drawImage(biInner, x, y, null);
            g.dispose();

            ImageIO.write(biOutter, "PNG", new File("Outter.png"));
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

I'd also double check shuangwhywhy suggestion of making sure you not reading in the same file twice ... I did that some thing when testing the code :P

score 1 · Answer 3 · answered Feb 02 '13 at 13:29

1

You can also try SRC_ATOP with the transparency 0.5.

answered Feb 02 '13 at 13:29

Audrius Meškauskas

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Java: Merging 2 images is not working

3 Answers3