Question

Is there any way to increase the width (or height) of a Bitmap without stretching it? Basically, I have a 200×100 bitmap and I want to make it square (200×200) by appending 50 (white / transparent) pixels to the left and 50 pixels to the right.

I don’t want to draw this Bitmap on the screen so, ideally, I should be using a transformation Matrix in a “smart” way or something like that, but I just can’t figure it out…

Answer 1

You may try something like this:

        // creating a dummy bitmap
        Bitmap source = Bitmap.createBitmap(100, 200, Bitmap.Config.ARGB_8888);
        Bitmap background;
        Canvas canvas;

        if(source.getHeight() == source.getWidth()) // do nothing
            return;

        // create a new Bitmap with the bigger side (to get a square)
        if(source.getHeight() > source.getWidth()) {
            background = Bitmap.createBitmap(source.getHeight(), source.getHeight(), Bitmap.Config.ARGB_8888);
            canvas = new Canvas(background);
            // draw the source image centered
            canvas.drawBitmap(source, source.getHeight()/4, 0, new Paint());
        } else {
            background = Bitmap.createBitmap(source.getWidth(), source.getWidth(), Bitmap.Config.ARGB_8888);
            canvas = new Canvas(background);
            // draw the source image centered
            canvas.drawBitmap(source, 0, source.getWidth()/4, new Paint());
        }

        source.recycle();
        canvas.setBitmap(null);
        // update the source image
        source = background;

Note: The black border is not part of the image. I chose dark red as a background color to see the actual size of the image and to distinguish it from black and the source image’s color (which is always painted centered).

By drawing it on a Canvas it is not visible on the screen. I used an ImageView just to test the code.

Here is the output I get for w=200,h=100:

Here is the output I get for w=100,h=200: