Resize Bitmap according to the maximum allowed size (width or height) in dp

ResizeBitmap.java

public final class BitmapUtility {

    private BitmapUtility() {

    }

    // scale the bitmap for a given maximum dimension
    // (width or height depending on the image's aspect ratio)
    public static Bitmap scaleBitmap(Bitmap bitmap, int dp, Context context) {
        int width = bitmap.getWidth();
        int height = bitmap.getHeight();
        int bounding = dpToPx(dp, context);

        // Determine how much to scale: the dimension requiring less scaling is
        // closer to the its side. This way the image always stays inside your
        // bounding box AND either x/y axis touches it.
        float xScale = ((float) bounding) / width;
        float yScale = ((float) bounding) / height;
        float scale = (xScale <= yScale) ? xScale : yScale;

        // Create a matrix for the scaling and add the scaling data
        Matrix matrix = new Matrix();
        matrix.postScale(scale, scale);

        return Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true);
    }

    // convert from device-dependent density pixels to raw pixels
    private static int dpToPx(int dp, Context context) {
        float density = context.getResources().getDisplayMetrics().density;
        return Math.round((float) dp * density);
    }    
}