Java ImageJ - 如何使图像透明？

Question

I'd ask, how can I make an image transparent?

Actually, I tried to read RGB Values from IndexColorModel

ImageProcessor ip1 = img1.getProcessor();
IndexColorModel indexColor = (IndexColorModel)ip1.getColorModel();

then read a parameters wich i need to create new IndexColorModel

int pixelBits = indexColor .getPixelSize();

int mapSize = cm.getMapSize();
byte[] reds = new byte[mapSize];
cm.getReds(reds);

byte[] greens = new byte[mapSize];
cm.getGreens(greens);

byte[] blues = new byte[mapSize];
cm.getBlues(blues);

and create new IndexColorModel and set it to another ImagePlus with different transparentIndex

indexColor = new IndexColorModel(pixelBits, MapSize, reds, greens, blues, transparentIndex );
ImageProcessor ip3;
ip3.setColorModel(indexColor);

but this is wrong idea...

Should I use IndexColorModel with cmap and hasAlpha parameters? How can I do this?

Thank you in advance for help!

Answer 1

I'd ask, how can I make an image transparent?

That is too much work to make an image transparent. For a input image of type BufferedImage I would just do:

1. Create a new temporary BufferedImage tmpImage with the same size to image and type: BufferedImage.TYPE_INT_ARGB
2. Get it's graphics of the tmpImage and convert it to Graphics2D by up-casting.
3. set alpha composite to the Graphics2D instance with the transparency level i need
4. Draw the image and get done with it.

For example:

   BufferedImage tmpImg = new BufferedImage(image.getWidth(), image.getHeight(), 
                                                  BufferedImage.TYPE_INT_ARGB);
   Graphics2D g2d = (Graphics2D) tmpImg.getGraphics();
   g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f)); 
            // set the transparency level in range 0.0f - 1.0f 
   g2d.drawImage(image, 0, 0, null);
   image = tmpImg;