package ch.claude_martin.foo;

import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

public class SomeClass {
	public static void main(String[] args) throws IOException {
		var input = "C:/picture.jpg";
		var output = "C:/rotated_picture.jpg";
		var img = ImageIO.read(new File(input));
		var rotated = rotateBufferedImage(img, -90);
		ImageIO.write(rotated, "jpg", new File(output));
	}

	/**
	 * Rotates an image. Note that an angle of -90 is equal to 270.
	 * 
	 * @param img   The image to be rotated
	 * @param angle The angle in degrees (must be a multiple of 90°).
	 * @return The rotated image, or the original image, if the effective angle is
	 *         0°.
	 */
	public static BufferedImage rotateBufferedImage(BufferedImage img, int angle) {
		if (angle < 0) {
			angle = 360 + (angle % 360);
		}
		if ((angle %= 360) == 0) {
			return img;
		}
		final boolean r180 = angle == 180;
		if (angle != 90 && !r180 && angle != 270)
			throw new IllegalArgumentException("Invalid angle.");
		final int w = r180 ? img.getWidth() : img.getHeight();
		final int h = r180 ? img.getHeight() : img.getWidth();
		final int type = img.getType() == BufferedImage.TYPE_CUSTOM ? BufferedImage.TYPE_INT_ARGB : img.getType();
		final BufferedImage rotated = new BufferedImage(w, h, type);
		final Graphics2D graphic = rotated.createGraphics();
		graphic.rotate(Math.toRadians(angle), w / 2d, h / 2d);
		final int offset = r180 ? 0 : (w - h) / 2;
		graphic.drawImage(img, null, offset, -offset);
		graphic.dispose();
		return rotated;
	}

}