How to draw on bitmap using another bitmap as mask?

问题

I want to draw on a bitmap using another bitmap as mask. The mask is a black bitmap with a transparent object in it. I want this transparent part to be filled with an arbitrary color and added to my original image. How can this be done?

+

+ blue color =

回答1:

I had to change the masks as described by @Christian. Then, the wanted result could easily be produced:

canvas.drawRect(rect, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
canvas.drawBitmap(mask, 0.0f, 0.0f, paint);

回答2:

If you're setting this to an ImageView, a quick way is to set the background to the gradient drawable, and a blue 'T' with a transparent background as the ImageView's source. Not fancy, but fast and simple!

来源：https://stackoverflow.com/questions/17835435/how-to-draw-on-bitmap-using-another-bitmap-as-mask