Save transformed BufferedImage

[Samuel Goldschmidt]

Hello community,
I want to load an image from the hard disk, then rotate it by 90° and then save the rotated version to another file. However, the following doesn't work:

import java.awt.image.*;
import java.awt.*;
import java.util.regex.*;
import java.io.*;
import javax.imageio.*;

public class ImageRotate {

	public static void main(String[] args) throws IOException {
		BufferedImage im = ImageIO.read(new File("C:/a.png"));
		Graphics2D g = im.createGraphics();
		g.rotate(Math.PI / 2);
		ImageIO.write(im, "png", new File("C:/b.png"));
	}
}

Could you tell me what I am doing wrong and/or show me how it's done properly?

Regards,
Sam

[Martijn Verburg]

When you say it doesn't work, what doesn't? Are you seeing error messages or...?

[Rob Spoor]

You rotate the graphics object only, not the image itself.

Moving to Swing / AWT.

[Samuel Goldschmidt]

What doesn't work is: The saved image is not rotated.

[Rob Spoor]

Because you're not rotating the image. Rotating the Graphics object does not rotate the image. Perhaps you should check out the Java2D Tutorial

[Samuel Goldschmidt]

OK I've got it now. Does someone know how to do it correctly?

[Craig Wood]

BufferedImage src = ...
int w = src.getWidth();
int h = src.getHeight();
BufferedImage dst = new BufferedImage(h, w, src.getType());
Graphics2D g2 = dst.createGraphics();
g2.translate(h, 0);
g2.rotate(Math.PI/2);
g2.drawImage(src, 0, 0, null);
g2.dispose();
// write dst to file

[Samuel Goldschmidt]

Well, thanks a lot, Craig! This worked! (Save for the src.getType(), but I just put in src.TYPE_INT_RGB)
g2.drawImage(src, ...) is really cool. I think I didn't know what to do because I didn't know what g2.drawImage(...) does. I used it before to draw BufferedImages on JPanels, but actually it's a function which copies image data to specific memory locations, isn't it?

[Rob Spoor]

It depends on the Graphics object. For BufferedImage, it's an in-memory object. For components it can be regarded as a representation of the screen. When printing it can be regarded as a representation of a paper sheet.