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javaandroidbitmapopacityalpha

How to change a bitmap's opacity?

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?

Solution

  • You could also try BitmapDrawable instead of Bitmap. If this is useful for you depends on the way you use the bitmap...

    Edit

    As a commenter asked how he can store the bitmap with alpha, here is some code:

    // lets create a new empty bitmap
Bitmap newBitmap = Bitmap.createBitmap(originalBitmap.getWidth(), originalBitmap.getHeight(), Bitmap.Config.ARGB_8888);
// create a canvas where we can draw on
Canvas canvas = new Canvas(newBitmap);
// create a paint instance with alpha
Paint alphaPaint = new Paint();
alphaPaint.setAlpha(42);
// now lets draw using alphaPaint instance
canvas.drawBitmap(originalBitmap, 0, 0, alphaPaint);

// now lets store the bitmap to a file - the canvas has drawn on the newBitmap, so we can just store that one
// please add stream handling with try/catch blocks
FileOutputStream fos = new FileOutputStream(new File("/awesome/path/to/bitmap.png"));
newBitmap.compress(Bitmap.CompressFormat.PNG, 100, fos);