<dependency>　　<groupId>net.coobird</groupId>　　<artifactId>thumbnailator</artifactId>　　<version>0.4.8</version></dependency>

 1 package com.demo.test; 2  3 import java.awt.image.BufferedImage; 4 import java.io.File; 5 import java.io.IOException; 6 import java.math.BigDecimal; 7  8 import javax.imageio.ImageIO; 9 10 import org.slf4j.Logger;11 import org.slf4j.LoggerFactory;12 13 import com.longtime.app.image.web.ImageServlet;14 15 import net.coobird.thumbnailator.Thumbnails;16 import net.coobird.thumbnailator.Thumbnails.Builder;17 import net.coobird.thumbnailator.geometry.Positions;18 19 public class CovertUtils {20 21     /**22      * 23      * @param sourceFile24      *            源图片文件25      * @param targetFile26      *            目标图片文件27      * @param targetWidth28      *            目标图片文件宽 高29      * @param targetHeight30      *            目标图片文件 高31      * @throws IOException32      * @throws MagickException33      */34     public static void cover(String sourceFile, String targetFile, int targetWidth, int targetHeight) {35         File fromFile = new File(sourceFile);36         BufferedImage srcImage = null;37         int s_height = 0;38         int s_width = 0;39         try {40             srcImage = ImageIO.read(fromFile);41             // 获取源文件的宽高42             s_height = srcImage.getHeight();43             s_width = srcImage.getWidth(); 44             System.out.println(s_height + "");45             System.out.println(s_width + "");46         } catch (IOException e1) {47             e1.printStackTrace();48         }49         // 判断是否需要压缩50         if (targetWidth != s_width || targetHeight != s_height) {// 需要压缩51             BigDecimal n = new BigDecimal(s_height).divide(new BigDecimal(s_width), 10, BigDecimal.ROUND_UP);// 源图片文件高/宽  的比例52             BigDecimal m = new BigDecimal(targetHeight).divide(new BigDecimal(targetWidth), 10, BigDecimal.ROUND_UP);// 目标图片文件高/宽 的比例53             System.out.println(n+ "");54             System.out.println(m+ "");55             int flag = n.compareTo(m); //比较源图片文件和目标图片 的高/宽 比56             try {57                 if (flag == 0) {// n == m，高/宽 比一致, 无需裁减, 直接压缩58                     System.out.println("flag： " + flag);59                     Thumbnails.of(sourceFile).forceSize(targetWidth, targetHeight).toFile(targetFile);60                 } else { // 高/宽 比不一致，需要裁减61                     if (flag > 0) {// 高的比例 > 宽的比例，以宽的比例进行缩放， 需要裁减高62                         srcImage = Thumbnails.of(sourceFile).width(targetWidth).asBufferedImage();//以宽的比例进行缩放63                     } else if (flag < 0) {// n < m 高的比例 < 宽的比例，以高的比例进行缩放， 需要裁减宽64                         srcImage = Thumbnails.of(sourceFile).height(targetHeight).asBufferedImage();//以高的比例进行缩放65                     }66                     // 居中裁减67                     Builder<BufferedImage> builder = Thumbnails.of(srcImage)68                             .sourceRegion(Positions.CENTER, targetWidth, targetHeight).size(targetWidth, targetHeight);69                     builder.toFile(targetFile);70                 }71             } catch (IOException e) {72                 // TODO Auto-generated catch block73                 e.printStackTrace();74             }75         }76     }77 78     public static void main(String[] args) throws IOException {79         String sourceFile = "E://uploadimg//2014//12//6972df55641a4c5ca287a2cb1a86627c.png";//源文件80         String targetFile = "E://uploadimg//2014//12//6972df55641a4c5ca287a2cb1a86627c_400x800.png"; //处理之后的文件81         int width = 400; //处理之后文件的宽82         int height = 800; //处理之后文件的高83         try {84             cover(sourceFile, targetFile, width, height);85         } catch (Exception e) {86             e.printStackTrace();87         }88 89     }90 }