Question

I have an imageview, which uses matrix to scale/drag an image. Now I want to overlay another image. The matrix transformation should be applied to the combination of background and overlay.

I did overwrite onDraw and used

    canvas.drawBitmap(overlay, matrix, null);

whereas overlay is the new overlay, matrix is the currently applied matrix. This works fine. Unfortunately I can’t specify an offset at which the overlay shall appear on top of the background. This works

    canvas.drawBitmap(overlay, 50, 10, null);

but the overlay remains on that position, once I draw and scale the background again…

How can I accomplish an offset while drawing a bitmap with matrix applied?

Regards

Answer 1

You may need to create a new bitmap of approprite size where your overlay will be saved with the matrix transformation. Something like:

Bitmap overlay2 = Bitmap.createBitmap(....) 

Canvas c2 = new Canvas(overlay2);

c2.drawBitmap(overlay, matrix, null);

canvas.drawBitmap(overlay2, 50, 10, null);

The other way perhaps better is to do canvas.translate:

canvas.save();
canvas.translate(50,10);
canvas.drawBitmap(overlay, matrix, null); 
canvas.restore();