haojusheng

转载自：http://www.matrix.org.cn/thread.shtml?topicId=46332&forumId=49
        http://www.blogjava.net/itstarting/archive/2007/07/26/132499.html


java自身的类，生成的缩略图一旦小于100px就变得参不认睹。
经过几天同事的功能的努力，总结以下经验，希望有所帮助。
现在介绍使用Jmagick的使用，可以生成质量很好的缩略图，当然还有其他很多图像处理的方法。

   首先jmagick（http://www.yeo.id.au/jmagick/）是ImageMagick（http: //www.imagemagick.org/）的java 应用的接口。所以要先安装ImageMagick应用程序，你的java应用才能使用,在主页上你可以轻松找到下载的链接。

   1。下载jmagick,imagemagick

   2.安装ImageMagick，网站上有安装方法（windows,unnix）,我只在win上做了安装，安装以后把安装目录下所有的dll文件copy到windows/system32/目录下。

   3。下载的jmagick包含jmagick.jar,jmagick.dll文件，jmagick.dll需要copy到windows/system32/目录下。

   4。web应用如果部署到tomcat下，那么最好在catalina.bat文件中改变如下设置

set JAVA_OPTS=%JAVA_OPTS% -Xms256M -Xmx768M -XX:MaxPermSize=128M -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.util.logging.config.file="${catalina.base}\conf\logging.properties"

   避免heap溢出的问题，参数看你自己的机器而定。（ -Xms256M -Xmx768M -XX:MaxPermSize=128M ）

   5。还要注意如果部署到web应用，你在使用的class里面需要

      System.setProperty("jmagick.systemclassloader","no");

     要不然会报出UnsatisfiedLinkError: no JMagick in java.library.path.

     实例如下：

public void resize(int w, int h) throws IOException {

        try {
         // Resize
          System.setProperty("jmagick.systemclassloader","no");
         ImageInfo info = new ImageInfo(sourceFileName);
         MagickImage image = new MagickImage(info);
         MagickImage scaled = image.scaleImage(w, h);//小图片文件的大小.
         scaled.setFileName(destFile);
         scaled.writeImage(info);

       }  catch(MagickApiException ex) {
        System.out.println(ex);

       }  catch(MagickException ex) {
        System.out.println(ex);
       }
    }

注：linux系统下，需要下载另外的包





jmagick的安装（基于windows），精简版步骤：
1、下载jmagick-win-5.5.7-Q8.zip，并把jmagick.jar放到应用的lib下，jmagick.dll拷贝到SYSTEM32下；
2、安装ImageMagick-5.5.7-Q8-windows-dll.exe软件
3、重新启动机器
麻烦点，但对图片的处理能力，确实超乎想象的（不过用6.2.6版本频频出现JVM Crach，吓死）

jmagick的使用，我只用了图片缩放，还可以。
代码如下：
   System.setProperty("jmagick.systemclassloader", "no");//这个没什么好说的，照办就是了
   ImageInfo info = new ImageInfo(fromFileName);
   MagickImage fromImage = new MagickImage(info);
   Dimension dim = fromImage.getDimension();
   double w = dim.getWidth();
   double h = dim.getHeight();
   int toHeight = (int)(h*toWidth/w);//按宽度比例缩放
     
   MagickImage toImage = fromImage.scaleImage(toWidth, toHeight);//缩放操作
   toImage.setFileName(toFileName);//设置输出的文件名
   toImage.writeImage(info); //保存


过程中发现最新版本的诸多问题，要么NoClassDefFoundError要么Can't find dependent libraries，简直不胜其烦。

后来降级到5.5.7，就好了，说明IT人唯最新版本是从的想法不一定正确。

说心里话，过程中曾经出现过多次JVM crach，现在还有心理阴影。


JMagick under Ubuntu 8.04
Finally I got it work

Environment:
Ubuntu 8.04
ImageMagick 6.3.7
Resin 3.1.6
JDK 1.6


过程如下：
使用Ubuntu内置的ImageMagick包
sudo apt-get install imagemagick

从JMagick的SVN上获取源代码
svn co https://jmagick.svn.sourceforge.net/svnroot/jmagick jmagick

命令行下，进入jmagick目录，按照INSTALL中的说明进行安装1
在第4步，configure script这步，我加了一些额外参数：
./configure --prefix=/home/Nick/jmagick --with-java-home=/usr/lib/jvm/java-6-sun-1.6.0.06/ --with-javadoc-dir=/home/Nick/jmagick/doc
这样安装时，文件会安装到/home/Nick/jmagick目录下，生成的javadoc文档，会在/home/Nick/jmagick/doc下

安装完成后2，/home/Nick/jmagick/lib目录下会有三个文件：
jmagick-6.3.8.jar, libJMagick-6.3.8.so, libJMagick.so
其中libJMagick.so应该只是一个指向libJMagick-6.3.8.so的link

我看到resin根目录下的libexec会出现在java.library.path环境变量中，因此我在resin根目录下创建一个libexec目录（默认是不存在的）
将libJMagick-6.3.8.so拷贝到此目录下，重命名为libJMagick.so3

将jmagick-6.3.8.jar放到应用程序的WEB-INF/lib目录下
另外，需要在程序内，写入
System.setProperty("jmagick.systemclassloader","no");
防止JMagick找不到Class文件
为了简便，我直接写了一个ContextListener，在contextInitialized方法里调用上面一句代码

运行resin服务器，调用测试页面，生成Thumbnail成功～


Notes:
1. 需要在此步前，确保系统中包含有autoconf、gcc等程序；如果没有，apt-get即可
2. 我在make test时，首先是编译就不通过。发现lib下根本没有junit.jar，于是去junit.org下了一份，放到lib下，编译通过
但是，测试会失败(Tests run: 15,  Failures: 1,  Errors: 9)，原因不太清楚，不知道会不会有其他影响..
不过，确实能够正常生成Thumbnail文件
3. 如果不拷贝过来，直接export LD_LIBRARY_PATH=/home/Nick/jmagick/lib好像也是可以的
这个根据个人的安装喜好来就可以了，呵呵


Referrence:
http://www.darcynorman.net/2005/03/15/jai-vs-imagemagick-image-resizing/ 这篇作者比较了JAI和ImageMagick的生成效果，并使用Runtime.exec的方式调用ImageMagick命令，而不是通过JMagick的JNI来调用ImageMagick。如果你对JMagick提供的API和调用方式不满，不妨看看这篇 =)



java算法，图片质量已经和ImageMagick不相上下，原理就是采用lancozs正弦曲线，对图片分别进行水平和垂直滤波采样。性能还有待高手帮助提高，比ImageMagick差不多有四五倍的差距。
                                                                                                             by 阿飞
import java.awt.image.BufferedImage;

public class ImageScale {
        private int width;
        private int height;
        private int scaleWidth;
        double support = (double) 3.0;
        double PI = (double) 3.14159265358978;
        double[] contrib;
        double[] normContrib;
        double[] tmpContrib;
        int startContrib, stopContrib;
        int nDots;
        int nHalfDots;

        /**
         * Start:
         * Use Lanczos filter to replace the original algorithm for image scaling. Lanczos improves quality of the scaled image
         * modify by :blade
         * */
        public BufferedImage imageZoomOut(BufferedImage srcBufferImage,int w, int h) {
                width = srcBufferImage.getWidth();
                height = srcBufferImage.getHeight();
                scaleWidth = w;

                if (DetermineResultSize(w, h) == 1) {
                        return srcBufferImage;
                }
                CalContrib();
                BufferedImage pbOut = HorizontalFiltering(srcBufferImage, w);
                BufferedImage pbFinalOut = VerticalFiltering(pbOut, h);
                return pbFinalOut;
        }

        /**
         * 决定图像尺寸
         * */
        private int DetermineResultSize(int w, int h) {
                double scaleH, scaleV;
                scaleH = (double) w / (double) width;
                scaleV = (double) h / (double) height;
                //需要判断一下scaleH，scaleV，不做放大操作
                if (scaleH >= 1.0 && scaleV >= 1.0) {
                        return 1;
                }
                return 0;

        } // end of DetermineResultSize()

        private double Lanczos(int i, int inWidth, int outWidth, double Support) {
                double x;

                x = (double) i * (double) outWidth / (double) inWidth;

                return Math.sin(x * PI) / (x * PI) * Math.sin(x * PI / Support)
                                / (x * PI / Support);

        } // end of Lanczos()

        //
        //   Assumption: same horizontal and vertical scaling factor
        //
        private void CalContrib() {
                nHalfDots = (int) ((double) width * support / (double) scaleWidth);
                nDots = nHalfDots * 2 + 1;
                try {
                        contrib = new double[nDots];
                        normContrib = new double[nDots];
                        tmpContrib = new double[nDots];
                } catch (Exception e) {
                        System.out.println("init contrib,normContrib,tmpContrib" + e);
                }

                int center = nHalfDots;
                contrib[center] = 1.0;

                double weight = 0.0;
                int i = 0;
                for (i = 1; i <= center; i++) {
                        contrib[center + i] = Lanczos(i, width, scaleWidth, support);
                        weight += contrib[center + i];
                }

                for (i = center - 1; i >= 0; i--) {
                        contrib[i] = contrib[center * 2 - i];
                }

                weight = weight * 2 + 1.0;

                for (i = 0; i <= center; i++) {
                        normContrib[i] = contrib[i] / weight;
                }

                for (i = center + 1; i < nDots; i++) {
                        normContrib[i] = normContrib[center * 2 - i];
                }
        } // end of CalContrib()

        //处理边缘
        private void CalTempContrib(int start, int stop) {
                double weight = 0;

                int i = 0;
                for (i = start; i <= stop; i++) {
                        weight += contrib[i];
                }

                for (i = start; i <= stop; i++) {
                        tmpContrib[i] = contrib[i] / weight;
                }

        } // end of CalTempContrib()

        private int GetRedValue(int rgbValue) {
                int temp = rgbValue & 0x00ff0000;
                return temp >> 16;
        }

        private int GetGreenValue(int rgbValue) {
                int temp = rgbValue & 0x0000ff00;
                return temp >> 8;
        }

        private int GetBlueValue(int rgbValue) {
                return rgbValue & 0x000000ff;
        }

        private int ComRGB(int redValue, int greenValue, int blueValue) {

                return (redValue << 16) + (greenValue <<+ blueValue;
        }

        //行水平滤波
        private int HorizontalFilter(BufferedImage bufImg, int startX, int stopX,
                        int start, int stop, int y, double[] pContrib) {
                double valueRed = 0.0;
                double valueGreen = 0.0;
                double valueBlue = 0.0;
                int valueRGB = 0;
                int i, j;

                for (i = startX, j = start; i <= stopX; i++, j++) {
                        valueRGB = bufImg.getRGB(i, y);

                        valueRed += GetRedValue(valueRGB) * pContrib[j];
                        valueGreen += GetGreenValue(valueRGB) * pContrib[j];
                        valueBlue += GetBlueValue(valueRGB) * pContrib[j];
                }

                valueRGB = ComRGB(Clip((int) valueRed), Clip((int) valueGreen),
                                Clip((int) valueBlue));
                return valueRGB;

        } // end of HorizontalFilter()

        //图片水平滤波
        private BufferedImage HorizontalFiltering(BufferedImage bufImage, int iOutW) {
                int dwInW = bufImage.getWidth();
                int dwInH = bufImage.getHeight();
                int value = 0;
                BufferedImage pbOut = new BufferedImage(iOutW, dwInH,
                                BufferedImage.TYPE_INT_RGB);

                for (int x = 0; x < iOutW; x++) {

                        int startX;
                        int start;
                        int X = (int) (((double) x) * ((double) dwInW) / ((double) iOutW) + 0.5);
                        int y = 0;

                        startX = X - nHalfDots;
                        if (startX < 0) {
                                startX = 0;
                                start = nHalfDots - X;
                        } else {
                                start = 0;
                        }

                        int stop;
                        int stopX = X + nHalfDots;
                        if (stopX > (dwInW - 1)) {
                                stopX = dwInW - 1;
                                stop = nHalfDots + (dwInW - 1 - X);
                        } else {
                                stop = nHalfDots * 2;
                        }

                        if (start > 0 || stop < nDots - 1) {
                                CalTempContrib(start, stop);
                                for (y = 0; y < dwInH; y++) {
                                        value = HorizontalFilter(bufImage, startX, stopX, start,
                                                        stop, y, tmpContrib);
                                        pbOut.setRGB(x, y, value);
                                }
                        } else {
                                for (y = 0; y < dwInH; y++) {
                                        value = HorizontalFilter(bufImage, startX, stopX, start,
                                                        stop, y, normContrib);
                                        pbOut.setRGB(x, y, value);
                                }
                        }
                }

                return pbOut;

        } // end of HorizontalFiltering()

        private int VerticalFilter(BufferedImage pbInImage, int startY, int stopY,
                        int start, int stop, int x, double[] pContrib) {
                double valueRed = 0.0;
                double valueGreen = 0.0;
                double valueBlue = 0.0;
                int valueRGB = 0;
                int i, j;

                for (i = startY, j = start; i <= stopY; i++, j++) {
                        valueRGB = pbInImage.getRGB(x, i);

                        valueRed += GetRedValue(valueRGB) * pContrib[j];
                        valueGreen += GetGreenValue(valueRGB) * pContrib[j];
                        valueBlue += GetBlueValue(valueRGB) * pContrib[j];
                        //                  System.out.println(valueRed+"->"+Clip((int)valueRed)+"<-");
                        //
                        //                  System.out.println(valueGreen+"->"+Clip((int)valueGreen)+"<-");
                        //                  System.out.println(valueBlue+"->"+Clip((int)valueBlue)+"<-"+"-->");
                }

                valueRGB = ComRGB(Clip((int) valueRed), Clip((int) valueGreen),
                                Clip((int) valueBlue));
                //           System.out.println(valueRGB);
                return valueRGB;

        } // end of VerticalFilter()

        private BufferedImage VerticalFiltering(BufferedImage pbImage, int iOutH) {
                int iW = pbImage.getWidth();
                int iH = pbImage.getHeight();
                int value = 0;
                BufferedImage pbOut = new BufferedImage(iW, iOutH,
                                BufferedImage.TYPE_INT_RGB);

                for (int y = 0; y < iOutH; y++) {

                        int startY;
                        int start;
                        int Y = (int) (((double) y) * ((double) iH) / ((double) iOutH) + 0.5);

                        startY = Y - nHalfDots;
                        if (startY < 0) {
                                startY = 0;
                                start = nHalfDots - Y;
                        } else {
                                start = 0;
                        }

                        int stop;
                        int stopY = Y + nHalfDots;
                        if (stopY > (int) (iH - 1)) {
                                stopY = iH - 1;
                                stop = nHalfDots + (iH - 1 - Y);
                        } else {
                                stop = nHalfDots * 2;
                        }

                        if (start > 0 || stop < nDots - 1) {
                                CalTempContrib(start, stop);
                                for (int x = 0; x < iW; x++) {
                                        value = VerticalFilter(pbImage, startY, stopY, start, stop,
                                                        x, tmpContrib);
                                        pbOut.setRGB(x, y, value);
                                }
                        } else {
                                for (int x = 0; x < iW; x++) {
                                        value = VerticalFilter(pbImage, startY, stopY, start, stop,
                                                        x, normContrib);
                                        pbOut.setRGB(x, y, value);
                                }
                        }

                }

                return pbOut;

        } // end of VerticalFiltering()

        int Clip(int x) {
                if (x < 0)
                        return 0;
                if (x > 255)
                        return 255;
                return x;
        }

        /**
         * End:
         * Use Lanczos filter to replace the original algorithm for image scaling. Lanczos improves quality of the scaled image
         * modify by :blade
         * */
}