完整代码如下:
/*
* Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in the
*     documentation and/or other materials provided with the distribution.
*
*   - Neither the name of Oracle or the names of its
*     contributors may be used to endorse or promote products derived
*     from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import java.awt.image.BufferedImage;
import java.io.File;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveAction;
import javax.imageio.ImageIO;
/**
* ForkBlur implements a simple horizontal image blur. It averages pixels in the
* source array and writes them to a destination array. The sThreshold value
* determines whether the blurring will be performed directly or split into two
* tasks.
*
* This is not the recommended way to blur images; it is only intended to
* illustrate the use of the Fork/Join framework.
*/
public class ForkBlur extends RecursiveAction {
private static final long serialVersionUID = -8032915917030559798L;
private int[] mSource;
private int mStart;
private int mLength;
private int[] mDestination;
private int mBlurWidth = 15; // Processing window size, should be odd.
public ForkBlur(int[] src, int start, int length, int[] dst) {
mSource = src;
mStart = start;
mLength = length;
mDestination = dst;
}
// Average pixels from source, write results into destination.
protected void computeDirectly() {
int sidePixels = (mBlurWidth - 1) / 2;
for (int index = mStart; index < mStart + mLength; index++) {
// Calculate average.
float rt = 0, gt = 0, bt = 0;
for (int mi = -sidePixels; mi <= sidePixels; mi++) {
int mindex = Math.min(Math.max(mi + index, 0), mSource.length - 1);
int pixel = mSource[mindex];
rt += (float) ((pixel & 0x00ff0000) >> 16) / mBlurWidth;
gt += (float) ((pixel & 0x0000ff00) >> 8) / mBlurWidth;
bt += (float) ((pixel & 0x000000ff) >> 0) / mBlurWidth;
}
// Re-assemble destination pixel.
int dpixel = (0xff000000)
| (((int) rt) << 16)
| (((int) gt) << 8)
| (((int) bt) << 0);
mDestination[index] = dpixel;
}
}
protected static int sThreshold = 10000;
@Override
protected void compute() {
if (mLength < sThreshold) {
computeDirectly();
return;
}
int split = mLength / 2;
invokeAll(new ForkBlur(mSource, mStart, split, mDestination),
new ForkBlur(mSource, mStart + split, mLength - split,
mDestination));
}
// Plumbing follows.
public static void main(String[] args) throws Exception {
String srcName = "C:\test6.jpg";
File srcFile = new File(srcName);
BufferedImage image = ImageIO.read(srcFile);
System.out.println("Source image: " + srcName);
BufferedImage blurredImage = blur(image);
String dstName = "C:\test6_out.jpg";
File dstFile = new File(dstName);
ImageIO.write(blurredImage, "jpg", dstFile);
System.out.println("Output image: " + dstName);
}
public static BufferedImage blur(BufferedImage srcImage) {
int w = srcImage.getWidth();
int h = srcImage.getHeight();
int[] src = srcImage.getRGB(0, 0, w, h, null, 0, w);
int[] dst = new int[src.length];
System.out.println("Array size is " + src.length);
System.out.println("Threshold is " + sThreshold);
int processors = Runtime.getRuntime().availableProcessors();
System.out.println(Integer.toString(processors) + " processor"
+ (processors != 1 ? "s are " : " is ")
+ "available");
ForkBlur fb = new ForkBlur(src, 0, src.length, dst);
ForkJoinPool pool = new ForkJoinPool();
long startTime = System.currentTimeMillis();
pool.invoke(fb);
long endTime = System.currentTimeMillis();
System.out.println("Image blur took " + (endTime - startTime) +
" milliseconds.");
BufferedImage dstImage =
new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
dstImage.setRGB(0, 0, w, h, dst, 0, w);
return dstImage;
}
}
  测试了一下,执行效果如下:
  Source image: C: est6.jpg
  Array size is 120000
  Threshold is 10000
  4 processors are available
  Image blur took 10 milliseconds.
  Output image: C: est6_out.jpg

  JDK中使用fork/join的例子
  除了我们上面提到的使用fork/join框架并行执行图像模糊任务之外,在JAVA SE中,也已经利用fork/join框架实现了一些非常有用的特性。其中一个实现是在JAVA SE8 中java.util.Arrays 类的parallelSort()方法。这些方法和sort()方法类似,但是可以通过fork/join框架并行执行。对于大数组排序,在多核处理器系统中,使用并行排序方法比顺序排序更加高效。当然,关于这些排序方法是如何利用fork/join框架不在本篇文章讨论范围,更多信息可以查看JAVA API文档。