Scaled Bitmap maintaining aspect ratio

Question

I would like to scale a Bitmap to a runtime dependant width and height, where the aspect ratio is maintained and the Bitmap fills the entire width

Answer 1

None of the above answers were worked for me and I just created a method which sets all of the dimensions into the desired ones with painting the empty area to black. Here is my method:

/**
 * Scale the image preserving the ratio
 * @param imageToScale Image to be scaled
 * @param destinationWidth Destination width after scaling
 * @param destinationHeight Destination height after scaling
 * @return New scaled bitmap preserving the ratio
 */
public static Bitmap scalePreserveRatio(Bitmap imageToScale, int destinationWidth,
        int destinationHeight) {
    if (destinationHeight > 0 && destinationWidth > 0 && imageToScale != null) {
        int width = imageToScale.getWidth();
        int height = imageToScale.getHeight();

        //Calculate the max changing amount and decide which dimension to use
        float widthRatio = (float) destinationWidth / (float) width;
        float heightRatio = (float) destinationHeight / (float) height;

        //Use the ratio that will fit the image into the desired sizes
        int finalWidth = (int)Math.floor(width * widthRatio);
        int finalHeight = (int)Math.floor(height * widthRatio);
        if (finalWidth > destinationWidth || finalHeight > destinationHeight) {
            finalWidth = (int)Math.floor(width * heightRatio);
            finalHeight = (int)Math.floor(height * heightRatio);
        }

        //Scale given bitmap to fit into the desired area
        imageToScale = Bitmap.createScaledBitmap(imageToScale, finalWidth, finalHeight, true);

        //Created a bitmap with desired sizes
        Bitmap scaledImage = Bitmap.createBitmap(destinationWidth, destinationHeight, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(scaledImage);

        //Draw background color
        Paint paint = new Paint();
        paint.setColor(Color.BLACK);
        paint.setStyle(Paint.Style.FILL);
        canvas.drawRect(0, 0, canvas.getWidth(), canvas.getHeight(), paint);

        //Calculate the ratios and decide which part will have empty areas (width or height)
        float ratioBitmap = (float)finalWidth / (float)finalHeight;
        float destinationRatio = (float) destinationWidth / (float) destinationHeight;
        float left = ratioBitmap >= destinationRatio ? 0 : (float)(destinationWidth - finalWidth) / 2;
        float top = ratioBitmap < destinationRatio ? 0: (float)(destinationHeight - finalHeight) / 2;
        canvas.drawBitmap(imageToScale, left, top, null);

        return scaledImage;
    } else {
        return imageToScale;
    }
}

For example;

Let's say you have an image as 100 x 100 but the desired size is 300x50, then this method will convert your image to 50 x 50 and paint it into a new image which has dimensions as 300 x 50 (and empty fileds will be black).

Another example: let's say you have an image as 600 x 1000 and the desired sizes are 300 x 50 again, then your image will be converted into 30 x 50 and painted into a newly created image which has sizes as 300 x 50.

I think this is what it must be, Rs.