让 Eclipse 插件程序具有二维作图能力（2）

import java.awt.Graphics2D;
import java.awt.image.BufferedImage;

import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.ImageData;
import org.eclipse.swt.graphics.PaletteData;
import org.eclipse.swt.widgets.Display;

/**
* Helper class allowing the use of Java 2D on SWT or Draw2D graphical
* context.
* @author Yannick Saillet
*/
public class Graphics2DRenderer {
private static final PaletteData PALETTE_DATA =
new PaletteData(0xFF0000, 0xFF00, 0xFF);

private BufferedImage awtImage;
private Image swtImage;
private ImageData swtImageData;
private int[] awtPixels;

/** RGB value to use as transparent color */
private static final int TRANSPARENT_COLOR = 0x123456;

/**
* Prepare to render on a SWT graphics context.
*/
public void prepareRendering(GC gc) {
org.eclipse.swt.graphics.Rectangle clip = gc.getClipping();
prepareRendering(clip.x, clip.y, clip.width, clip.height);
}

/**
* Prepare to render on a Draw2D graphics context.
*/
public void prepareRendering(org.eclipse.draw2d.Graphics graphics) {
org.eclipse.draw2d.geometry.Rectangle clip =
graphics.getClip(new org.eclipse.draw2d.geometry.Rectangle());
prepareRendering(clip.x, clip.y, clip.width, clip.height);
}

/**
* Prepare the AWT offscreen image for the rendering of the rectangular
* region given as parameter.
*/
private void prepareRendering(int clipX, int clipY, int clipW, int clipH) {
// check that the offscreen images are initialized and large enough
checkOffScreenImages(clipW, clipH);
// fill the region in the AWT image with the transparent color
java.awt.Graphics awtGraphics = awtImage.getGraphics();
awtGraphics.setColor(new java.awt.Color(TRANSPARENT_COLOR));
awtGraphics.fillRect(clipX, clipY, clipW, clipH);
}

/**
* Returns the Graphics2D context to use.
*/
public Graphics2D getGraphics2D() {
if (awtImage == null) return null;
return (Graphics2D) awtImage.getGraphics();
}

/**
* Complete the rendering by flushing the 2D renderer on a SWT graphical
* context.
*/
public void render(GC gc) {
if (awtImage == null) return;

org.eclipse.swt.graphics.Rectangle clip = gc.getClipping();
transferPixels(clip.x, clip.y, clip.width, clip.height);
gc.drawImage(swtImage, clip.x, clip.y, clip.width, clip.height,
clip.x, clip.y, clip.width, clip.height);
}

/**
* Complete the rendering by flushing the 2D renderer on a Draw2D
* graphical context.
*/
public void render(org.eclipse.draw2d.Graphics graphics) {
if (awtImage == null) return;

org.eclipse.draw2d.geometry.Rectangle clip =
graphics.getClip(new org.eclipse.draw2d.geometry.Rectangle());
transferPixels(clip.x, clip.y, clip.width, clip.height);
graphics.drawImage(swtImage, clip.x, clip.y, clip.width, clip.height,
clip.x, clip.y, clip.width, clip.height);
}

/**
* Transfer a rectangular region from the AWT image to the SWT image.
*/
private void transferPixels(int clipX, int clipY, int clipW, int clipH) {
int step = swtImageData.depth / 8;
byte[] data = swtImageData.data;
awtImage.getRGB(clipX, clipY, clipW, clipH, awtPixels, 0, clipW);
for (int i = 0; i < clipH; i++) {
int idx = (clipY + i) * swtImageData.bytesPerLine + clipX * step;
for (int j = 0; j < clipW; j++) {
int rgb = awtPixels[j + i * clipW];
for (int k = swtImageData.depth - 8; k >= 0; k -= 8) {
data[idx++] = (byte) ((rgb >> k) & 0xFF);
}
}
}
if (swtImage != null) swtImage.dispose();
swtImage = new Image(Display.getDefault(), swtImageData);
}

/**
* Dispose the resources attached to this 2D renderer.
*/
public void dispose() {
if (awtImage != null) awtImage.flush();
if (swtImage != null) swtImage.dispose();
awtImage = null;
swtImageData = null;
awtPixels = null;
}

/**
* Ensure that the offscreen images are initialized and are at least
* as large as the size given as parameter.
*/
private void checkOffScreenImages(int width, int height) {
int currentImageWidth = 0;
int currentImageHeight = 0;
if (swtImage != null) {
currentImageWidth = swtImage.getImageData().width;
currentImageHeight = swtImage.getImageData().height;
}

// if the offscreen images are too small, recreate them
if (width > currentImageWidth || height > currentImageHeight) {
dispose();
width = Math.max(width, currentImageWidth);
height = Math.max(height, currentImageHeight);
awtImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
swtImageData = new ImageData(width, height, 24, PALETTE_DATA);
swtImageData.transparentPixel = TRANSPARENT_COLOR;
awtPixels = new int[width * height];
}
}
}