Using Image as alpha layter

Question

I'm reading an Image from a ByteArrayInputStream. This image is purely black-and-white, where the white parts of it should be transparent and the black parts should not. The problem is, the white parts are not transparent.
Is it possible to create an alpha mask from this image, where all white pixels are included in the mask, and then apply this alpha mask onto the original image (which is actually the same image, without being converted to an alpha mask), so only the black pixels are displayed?
Are there any alternative solution if this isn't possible? I'm a bit out of ideas myself at this point :/
(Sorry for the cross-post: http://forum.java.sun.com/thread.jsp?forum=5&thread=485556&tstart=0&trange=15)

Answer 1

This might help.
public static void makeTransparent(BufferedImage bImage, Color color) {
int markColor = color.getRGB() | 0xFF000000;
for (int y=0; y<bImage.getHeight(); y++ ) {
for (int x=0; x<bImage.getWidth(); x++ ) {
int col = bImage.getRGB(x,y);
if ( ( col | 0xFF000000 ) == markColor ) {
bImage.setRGB(x,y, 0x00FFFFFF & col); // Mark the alpha bits as zero - transparent
just do this:
(u have to have some Image image)
int w = image.getWidth(null);
int h = image.getHeight(null);
BufferedImage sBuf = new BufferedImage(w,h, BufferedImage.TYPE_INT_ARGB);
sBuf.getGraphics().drawImage(image, 0,0, null);
makeTransparent(sBuf, new Color(0,0,0)); // for black to transparent
voila.
did it help ?