Rotating and flipping an image in SWT

[Java Tip]

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.ImageData;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class Snippet139 {

  static ImageData rotate(ImageData srcData, int direction) {
    int bytesPerPixel = srcData.bytesPerLine / srcData.width;
    int destBytesPerLine = (direction == SWT.DOWN) ? srcData.width
        * bytesPerPixel : srcData.height * bytesPerPixel;
    byte[] newData = new byte[srcData.data.length];
    int width = 0, height = 0;
    for (int srcY = 0; srcY < srcData.height; srcY++) {
      for (int srcX = 0; srcX < srcData.width; srcX++) {
        int destX = 0, destY = 0, destIndex = 0, srcIndex = 0;
        switch (direction) {
        case SWT.LEFT: // left 90 degrees
          destX = srcY;
          destY = srcData.width - srcX - 1;
          width = srcData.height;
          height = srcData.width;
          break;
        case SWT.RIGHT: // right 90 degrees
          destX = srcData.height - srcY - 1;
          destY = srcX;
          width = srcData.height;
          height = srcData.width;
          break;
        case SWT.DOWN: // 180 degrees
          destX = srcData.width - srcX - 1;
          destY = srcData.height - srcY - 1;
          width = srcData.width;
          height = srcData.height;
          break;
        }
        destIndex = (destY * destBytesPerLine)
            + (destX * bytesPerPixel);
        srcIndex = (srcY * srcData.bytesPerLine)
            + (srcX * bytesPerPixel);
        System.arraycopy(srcData.data, srcIndex, newData, destIndex,
            bytesPerPixel);
      }
    }
    // destBytesPerLine is used as scanlinePad to ensure that no padding is
    // required
    return new ImageData(width, height, srcData.depth, srcData.palette,
        destBytesPerLine, newData);
  }

  static ImageData flip(ImageData srcData, boolean vertical) {
    int bytesPerPixel = srcData.bytesPerLine / srcData.width;
    int destBytesPerLine = srcData.width * bytesPerPixel;
    byte[] newData = new byte[srcData.data.length];
    for (int srcY = 0; srcY < srcData.height; srcY++) {
      for (int srcX = 0; srcX < srcData.width; srcX++) {
        int destX = 0, destY = 0, destIndex = 0, srcIndex = 0;
        if (vertical) {
          destX = srcX;
          destY = srcData.height - srcY - 1;
        } else {
          destX = srcData.width - srcX - 1;
          destY = srcY;
        }
        destIndex = (destY * destBytesPerLine)
            + (destX * bytesPerPixel);
        srcIndex = (srcY * srcData.bytesPerLine)
            + (srcX * bytesPerPixel);
        System.arraycopy(srcData.data, srcIndex, newData, destIndex,
            bytesPerPixel);
      }
    }
    // destBytesPerLine is used as scanlinePad to ensure that no padding is
    // required
    return new ImageData(srcData.width, srcData.height, srcData.depth,
        srcData.palette, destBytesPerLine, newData);
  }

  public static void main(String[] args) {
    Display display = new Display();

    // create an image with the word "hello" on it
    final Image image0 = new Image(display, 50, 30);
    GC gc = new GC(image0);
    gc.setBackground(display.getSystemColor(SWT.COLOR_RED));
    gc.fillRectangle(image0.getBounds());
    gc.drawString("hello", 5, 5, true);
    gc.dispose();

    ImageData data = image0.getImageData();
    // rotate and flip this image
    final Image image1 = new Image(display, rotate(data, SWT.LEFT));
    final Image image2 = new Image(display, rotate(data, SWT.RIGHT));
    final Image image3 = new Image(display, rotate(data, SWT.DOWN));
    final Image image4 = new Image(display, flip(data, true));
    final Image image5 = new Image(display, flip(data, false));

    Shell shell = new Shell(display);
    // draw the results on the shell
    shell.addPaintListener(new PaintListener() {
      public void paintControl(PaintEvent e) {
        e.gc.drawText("Original Image:", 10, 10, true);
        e.gc.drawImage(image0, 10, 40);
        e.gc.drawText("Left, Right, 180:", 10, 80, true);
        e.gc.drawImage(image1, 10, 110);
        e.gc.drawImage(image2, 50, 110);
        e.gc.drawImage(image3, 90, 110);
        e.gc.drawText("Flipped Vertical, Horizontal:", 10, 170, true);
        e.gc.drawImage(image4, 10, 200);
        e.gc.drawImage(image5, 70, 200);
      }
    });
    shell.setSize(300, 300);
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    image0.dispose();
    image1.dispose();
    image2.dispose();
    image3.dispose();
    image4.dispose();
    image5.dispose();
    display.dispose();
  }
}