How to combine two opaque bitmaps into one with alpha channel?

Question

I have a PNG file with transparency that I\'m using as OpenGL texture. I load it in Bitmap with BitmapFactory.decodeResource, then upload it to GPU.

Answer 1

Try the following: Iterate through width * height of your two images, and use Bitmap.getPixel(x,y) on each one.

int alpha = Color.red(grayscaleBitmap.getPixel(x, y)); // grayscale, so any color will do
int red = Color.red(colorBitmap.getPixel(x, y));
int green = Color.green(colorBitmap.getPixel(x, y));
int blue = Color.blue(colorBitmap.getPixel(x, y));
int mergedColor = Color.argb(alpha, red, green, blue);
// save mergedColor in an int[]

Then use Bitmap.createBitmap(int[] colors, int width, int height, Bitmap.Config config) to create your new bitmap.