java - Merging two images

Question

I need to merge two images (BufferedImage) in Java. It wouldn't be a problem if there was no transparency. The base image already has some transparency. I want to keep this as it is and apply a "mask" to it, the second image. This second image has no opaque pixels, in fact it's almost completely transparent, just has some less transparent pixels to give some sort of "light effect", like a reflex. Important detail: I don't want to do this on screen, with graphics, I need to obtain a BufferedImage with the resultant merge.

Can anyone help me? Thanks!

DETAILS: Merge two images maintaining transparency. This is what I need to do.

Note: this Set BufferedImage alpha mask in Java does not do what I need because it does not handle well with the two images having transparency - it modifies first picture transparency.

Answer 1

Just create a new BufferedImage with transparency, then paint the other two images (with full or semi-transparency) on it. This is how it will look like:

Sample code (images are called 'image.png' and 'overlay.png'):

File path = ... // base path of the images

// load source images
BufferedImage image = ImageIO.read(new File(path, "image.png"));
BufferedImage overlay = ImageIO.read(new File(path, "overlay.png"));

// create the new image, canvas size is the max. of both image sizes
int w = Math.max(image.getWidth(), overlay.getWidth());
int h = Math.max(image.getHeight(), overlay.getHeight());
BufferedImage combined = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);

// paint both images, preserving the alpha channels
Graphics g = combined.getGraphics();
g.drawImage(image, 0, 0, null);
g.drawImage(overlay, 0, 0, null);

g.dispose();

// Save as new image
ImageIO.write(combined, "PNG", new File(path, "combined.png"));