How to make Canvas draw area transparent in android?

Question

I would like to make Canvas area transparent because I would like to add an Image behind it so that Canvas actions happen above the image.My code for the canvas is here

Answer 1

well, I am not sure about drawing the transparent canvas, but in your case you can do a tweak, that draw the canvas using the background image iteself.

And then you can draw/ paint by finger on it.

Code example:

        BitmapDrawable bd = (BitmapDrawable)<YOUR_ACTIVITY>.this.getResources().getDrawable(R.drawable.<DRAWBLE_ID>);
        Bitmap b = bd.getBitmap();

        mBitmap = Bitmap.createBitmap(b,0,0,100,100); // This line is required only if you wanna some change in the bitmap you created
        mCanvas = new Canvas(mBitmap);

Answer 2

In your onDraw() method add this:

canvas.drawColor(0x00AAAAAA);

This will make your canvas transparent and background View will be visible.

Answer 3

You can create a Bitmap of the same size as the canvas. Erase all the colors of the bitmap using Color.TRANSPARENCY and set it as a canvas bitmap:

Bitmap transparentBitmap = Bitmap.createBitmap(canvas.getWidth(), canvas.getHeight(),
Bitmap.Config.ARGB_8888);
transparentBitmap.eraseColor(Color.TRANSPARENT);
canvas.setBitmap(transparentBitmap);