How to Rotate an image 90 Degrees in Java

Question

I'm working on an image processing app to rotate and image 90 degrees with this function, and could use some help with the logic. Integers i and j are coordinates, height and width are the total pixel height and width, rgb array is the color vavlues that need to be re-written into the new array. I know I need an array with height and width swapped, and I need to write the new color values into the correct locations, but I don't really know what to do.

Here is the function, any help would be appreciated.

private void rotate()

{

for(int i=0; i<height; i++)

   for(int j=0; j<width; j++)

   {    

      int rgbArray[] = new int[4];

      rgbArray = getPixelArray(picture[i][j]);

       picture[i][j] = getPixels(rgbArray);
    } 
 resetPicture();

}

Answer 1

I found a simple working example at https://blog.idrsolutions.com/2019/05/image-rotation-in-java/:

import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;

public class ImageRotator {

    public static void main(String[] args) throws  Exception {
        final double rads = Math.toRadians(90);
        final double sin = Math.abs(Math.sin(rads));
        final double cos = Math.abs(Math.cos(rads));

        File orgImage = new File("test.jpg");
        BufferedImage image = ImageIO.read(orgImage);

        final int w = (int) Math.floor(image.getWidth() * cos + image.getHeight() * sin);
        final int h = (int) Math.floor(image.getHeight() * cos + image.getWidth() * sin);
        final BufferedImage rotatedImage = new BufferedImage(w, h, image.getType());
        final AffineTransform at = new AffineTransform();
        at.translate(w / 2, h / 2);
        at.rotate(rads,0, 0);
        at.translate(-image.getWidth() / 2, -image.getHeight() / 2);
        final AffineTransformOp rotateOp = new AffineTransformOp(at, AffineTransformOp.TYPE_BILINEAR);
        rotateOp.filter(image,rotatedImage);



        ImageIO.write(rotatedImage, "JPG", new File(orgImage.getParentFile(),"new.jpg"));

    }
}