Resizing a bitmap to a fixed value but without changing the aspect ratio

Question

I'm looking for a solution for the following problem: how to change the size of a Bitmapto a fixed size (for example 512x128). The aspect ratio of the bitmap content must be preserved.

I think it should be something like this:

• create an empty 512x128 bitmap

• scale the original bitmap down to fit the 512x128 pixels with keeping the aspect ratio

• copy the scaled into the empty bitmap (centered)

What is the simplest way to achieve this?

The reason for all this is, that the GridView messes the layout up when the aspect ratio of an image differs from the other. Here is a screenshot (all images except the last one have the aspect ratio of 4:1):

screenshot

Answer 1

Try this, calculate the ratio and then rescale.

private Bitmap scaleBitmap(Bitmap bm) {
    int width = bm.getWidth();
    int height = bm.getHeight();

    Log.v("Pictures", "Width and height are " + width + "--" + height);

    if (width > height) {
        // landscape
        float ratio = (float) width / maxWidth;
        width = maxWidth;
        height = (int)(height / ratio);
    } else if (height > width) {
        // portrait
        float ratio = (float) height / maxHeight;
        height = maxHeight;
        width = (int)(width / ratio);
    } else {
        // square
        height = maxHeight;
        width = maxWidth;
    }

    Log.v("Pictures", "after scaling Width and height are " + width + "--" + height);

    bm = Bitmap.createScaledBitmap(bm, width, height, true);
    return bm;
}

Answer 2

The answer by Coen Damen doesn't always respect Max Height and Max Width. Here's an answer that does:

 private static Bitmap resize(Bitmap image, int maxWidth, int maxHeight) {
    if (maxHeight > 0 && maxWidth > 0) {
        int width = image.getWidth();
        int height = image.getHeight();
        float ratioBitmap = (float) width / (float) height;
        float ratioMax = (float) maxWidth / (float) maxHeight;

        int finalWidth = maxWidth;
        int finalHeight = maxHeight;
        if (ratioMax > 1) {
            finalWidth = (int) ((float)maxHeight * ratioBitmap);
        } else {
            finalHeight = (int) ((float)maxWidth / ratioBitmap);
        }
        image = Bitmap.createScaledBitmap(image, finalWidth, finalHeight, true);
        return image;
    } else {
        return image;
    }
}