How to change a bitmap's opacity?

java android bitmap opacity alpha
Mohit Deshpande picture Mohit Deshpande · Feb 25, 2011 · Viewed 60.4k times · Source

I have a bitmap:

Bitmap bitmap = BitmapFactory.decodeFile("some/arbitrary/path/image.jpg");

But I'm not going to display the image to the user. I want the alpha to be 100 (out of 255). If this is not possible, can I set the opacity of the Bitmap?

Answer

Matthew Willis picture Matthew Willis · Feb 25, 2011

As far as I know, opacity or other color filters can't be set on the Bitmap itself. You will need to set the alpha when you use the image:

If you're using ImageView, there is ImageView.setAlpha().

If you're using a Canvas, then you need to use Paint.setAlpha():

Paint paint = new Paint();
paint.setAlpha(100);
canvas.drawBitmap(bitmap, src, dst, paint);

Also, incorporating WarrenFaith's answer, if you will use the Bitmap where a drawable is required, you can use BitmapDrawable.setAlpha().

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