Java怎么实现自动生成缩略图片

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一、自动生成缩略图方法：

package writeimg; import java.awt.geom.AffineTransfORM;import java.awt.image.AffineTransformOp;import java.awt.image.BufferedImage;import java.io.File;import java.io.IOException;import javax.imageio.ImageIO; public class JpegTool {         private boolean isInitFlag = false; //         对象是否己经初始化         private String pic_big_pathfilename = null; //定义源图片所在的带路径目录的文件名        private String pic_small_pathfilename = null; // 生成小图片的带存放路径目录的文件名         private int smallpicwidth = 0; //定义生成小图片的宽度和高度，给其一个就可以了         private int smallpicheight = 0;         private int pic_big_width=0;        private int pic_big_height=0;        private double picscale = 0; //定义小图片的相比原图片的比例                  public JpegTool(){                this.isInitFlag = false;         }                  private void resetJpegToolParams(){                 this.picscale = 0;                 this.smallpicwidth = 0;                 this.smallpicheight = 0;                 this.isInitFlag = false;         }                  public void SetScale(double scale) throws JpegToolException        {                 if(scale<=0){                                 throw new JpegToolException(" 缩放比例不能为 0 和负数！ ");                 }                 this.resetJpegToolParams();                 this.picscale = scale;                 this.isInitFlag = true;         }                  public void SetSmallWidth(int smallpicwidth) throws JpegToolException         {                 if(smallpicwidth<=0)                {                         throw new JpegToolException(" 缩影图片的宽度不能为 0 和负数！ ");                 }                 this.resetJpegToolParams();                 this.smallpicwidth = smallpicwidth;                 this.isInitFlag = true;         }                    public void SetSmallHeight(int smallpicheight) throws JpegToolException {                 if(smallpicheight<=0)                {                    throw new JpegToolException(" 缩影图片的高度不能为 0 和负数！ ");                 }                 this.resetJpegToolParams();                 this.smallpicheight = smallpicheight;                 this.isInitFlag = true;         }                         public String getpic_big_pathfilename()        {                return this.pic_big_pathfilename;        }                public String getpic_small_pathfilename()        {                return this.pic_small_pathfilename;        }                public int getsrcw()        {                return this.pic_big_width;        }        public int getsrch()        {                return this.pic_big_height;        }                 public void doFinal(String pic_big_pathfilename,String pic_small_pathfilename) throws JpegToolException {                 if(!this.isInitFlag){                     throw new JpegToolException(" 对象参数没有初始化！ ");                 }                 if(pic_big_pathfilename==null || pic_small_pathfilename==null){                     throw new JpegToolException(" 包含文件名的路径为空！ ");                 }                 if((!pic_big_pathfilename.toLowerCase().endsWith("jpg")) && (!pic_big_pathfilename.toLowerCase().endsWith("jpeg"))){                     throw new JpegToolException(" 只能处理 JPG/JPEG 文件！ ");                 }                 if((!pic_small_pathfilename.toLowerCase().endsWith("jpg")) && !pic_small_pathfilename.toLowerCase().endsWith("jpeg")){                     throw new JpegToolException(" 只能处理 JPG/JPEG 文件！ ");                 }                 this.pic_big_pathfilename=pic_big_pathfilename;                this.pic_small_pathfilename=pic_small_pathfilename;                int smallw = 0;                 int smallh = 0;                 // 新建源图片和生成的小图片的文件对象                 File fi = new File(pic_big_pathfilename);                 File fo = new File(pic_small_pathfilename);                 //生成图像变换对象                 AffineTransform transform = new AffineTransform();                 //通过缓冲读入源图片文件                 BufferedImage bsrc = null;                 try {                 bsrc = ImageIO.read(fi);                 }catch (IOException ex) {                     throw new JpegToolException(" 读取源图像文件出错！ ");                 }                 this.pic_big_width= bsrc.getWidth();// 原图像的长度                 this.pic_big_height = bsrc.getHeight();// 原图像的宽度                 double scale = (double)pic_big_width/pic_big_height;// 图像的长宽比例                 if(this.smallpicwidth!=0)                {// 根据设定的宽度求出长度                         smallw = this.smallpicwidth;// 新生成的缩略图像的长度                         smallh = (smallw*pic_big_height)/pic_big_width ;// 新生成的缩略图像的宽度                 }                else if(this.smallpicheight!=0)                {// 根据设定的长度求出宽度                         smallh = this.smallpicheight;// 新生成的缩略图像的长度                         smallw = (smallh*pic_big_width)/pic_big_height;// 新生成的缩略图像的宽度                 }                else if(this.picscale!=0)                {// 根据设置的缩小比例设置图像的长和宽                         smallw = (int)((float)pic_big_width*this.picscale);                         smallh = (int)((float)pic_big_height*this.picscale);                 }                else                {                     throw new JpegToolException(" 对象参数初始化不正确！ ");                 }                double sx = (double)smallw/pic_big_width;//小/大图像的宽度比例                 double sy = (double)smallh/pic_big_height;//小/大图像的高度比例                 transform.setToScale(sx,sy);// 设置图像转换的比例                 //生成图像转换操作对象                 AffineTransformOp ato = new AffineTransformOp(transform,null);                 //生成缩小图像的缓冲对象                 BufferedImage bsmall = new BufferedImage(smallw,smallh,BufferedImage.TYPE_3BYTE_BGR);                 //生成小图像                 ato.filter(bsrc,bsmall);                 //输出小图像                 try{                        ImageIO.write(bsmall, "jpeg", fo);                 }                catch (IOException ex1)                 {                    throw new JpegToolException(" 写入缩略图像文件出错！ ");                 }         }}

二、异常处理类：

package jpegtool;     public class JpegToolException extends Exception {            private String errMsg = "";             public JpegToolException(String errMsg)             {                     this.errMsg = errMsg;             }              public String getMsg(){                 return "JpegToolException:"+this.errMsg;             }     }

三、调用的例子：

package writeimg; public class T {      public static void main(String[] args) {         JpegTool j = new JpegTool();        try {            j.SetScale(0.7);            j.SetSmallHeight(100);            j.doFinal("D:\\305\\c\\javatest\\src\\11.jpg","D:\\305\\c\\javatest\\src\\22.jpg");        } catch (JpegToolException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    } }

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