Image rotation - mapping the image into the center of the new image

Question

        for (int x = 1; x < imageOne.getWidth()-1 ; x++) {
            for (int y = 1; y < imageOne.getHeight()-1 ; y++) {
                /* Get the values from imageOne */
                int red = imageOne.getRed(x, y);
                int green = imageOne.getGreen(x, y);
                int blue = imageOne.getBlue(x, y);
                         * x' = a0x + a1y + a2
                         * y' = b0x + b1y + b2
                double x2 = Math.round(a0 * x + a1 * y);
                double y2 = Math.round(b0 * x + b1 * y);
                if (x2 > imageOne.getWidth()-1 || x2 < 0 || y2 < 0 || y2 > imageOne.getHeight()-1){
                    //Do Nothing
                }else{
                    imageTwo.setRGB((int)x2, (int)y2, red, green, blue);
        }Using the above algorithm, the image will rotate, but the rotation will start from the corner of the image (coordinate 1,1). For example, if I do a >90 degree angle rotation, the image will diappear.
I want my image to rotate and appear in the middle of the new image output.
Any idea?

Answer 1

Hi,
As part of my courseowrk, where we can't use the Java's API, im trying ot do the rotation manually...
Say my image is always 512x 512, and I've tried "translate" -> "rotate" -> "translate" below:
        for (int x = 1; x < imageOne.getWidth()-1 ; x++) {
            for (int y = 1; y < imageOne.getHeight()-1 ; y++) {
                /* Get the values from imageOne */
                int red = imageOne.getRed(x, y);
                int green = imageOne.getGreen(x, y);
                int blue = imageOne.getBlue(x, y);
                         * x' = a0x + a1y + a2
                         * y' = b0x + b1y + b2
                //1st transform
                x2 = x+256;
                y2 = y+256;
                 double rad = Math.toRadians(m);
        double cos = Math.cos(rad);
        double sin = Math.sin(rad);
        int newX = (int)Math.round(cos * getX() - sin * getY());
        int newY = (int)Math.round(sin * getX() + cos * getY());
        setX(newX);
        setY(newY);
                //2nd transform
                x2 = x2-256;
                y2=y2-256;
                if (x2 > imageOne.getWidth()-1 || x2 < 0 || y2 < 0 || y2 > imageOne.getHeight()-1){
                    //Do Nothing
                }else{
                    imageTwo.setRGB((int)x2, (int)y2, red, green, blue);
        }setX and setY will update the value in x2 and y2.
The concept is to move the pointer to the mid of the image (midHeight and midWidth) which is "x2 = x+256;" and "y2 = y+256;", rotate and translate again - but the output is still nto in the middle..
Any idea?