Android Mask bitmap on canvas gen a black space
android, bitmap, mask
Solution
Here is a solution which helped me to implement masking:
public void draw(Canvas canvas) {
Bitmap original = BitmapFactory.decodeResource(getContext().getResources(),R.drawable.original_image);
Bitmap mask = BitmapFactory.decodeResource(getContext().getResources(),R.drawable.mask_image);
//You can change original image here and draw anything you want to be masked on it.
Bitmap result = Bitmap.createBitmap(mask.getWidth(), mask.getHeight(), Config.ARGB_8888);
Canvas tempCanvas = new Canvas(result);
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
tempCanvas.drawBitmap(original, 0, 0, null);
tempCanvas.drawBitmap(mask, 0, 0, paint);
paint.setXfermode(null);
//Draw result after performing masking
canvas.drawBitmap(result, 0, 0, new Paint());
}
The mask should be a white image with transparency. It will work like this: + =
Problem
I have a mask bitmap with a half is red color and ones is transparent like this https://www.dropbox.com/s/931ixef6myzusi0/s_2.png I want to use mask bitmap to draw content on canvas only visible in red area, code like this: ``` Paint paint = new Paint(); public void draw(Canvas canvas) { // draw content here ... //and mask bitmap here paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.DST_IN)); canvas.drawBitmap(maskBitmap, 0, 0, paint); } ``` The result as my expecting (content only visible in red area, BUT THE TRANSPARENT AREA BECOME BLACK IS PROBLEM!) this image result :https://www.dropbox.com/s/mqj48992wllfkiq/s_2%20copy.png Anyone help me???