图片缩放与转换

通过对图片重绘，达到图片缩放、压缩编码转换功能。

      
 import java.awt.Image;  
 import java.awt.image.BufferedImage;  
 import java.awt.image.RenderedImage;  
 import java.io.File;  
 import java.io.InputStream;  
 import java.io.OutputStream;  
   
 import javax.imageio.ImageIO;  
   
 /** 
  *  
  * @author 梁栋 
  * @version 1.0 
  * @since 1.0 
  */  
 public abstract class ImageUtils {  
     /** 
      * 缩放图片 
      *  
      * @param width 
      *            输出宽度 
      * @param height 
      *            输出高度 
      * @param input 
      *            输入流 
      * @param output 
      *            输出流 
      * @param format 
      *            输出格式 
      * @return 
      * @throws Exception 
      */  
     public static boolean convert(int width, int height, InputStream input,  
             OutputStream output, String format) throws Exception {  
         // 输入  
         BufferedImage inputImage = ImageIO.read(input);  
         // 转换  
         RenderedImage im = (RenderedImage) convert(height, height, inputImage);  
         // 输出  
         return ImageIO.write(im, format, output);  
     }  
   
     /** 
      * 转换压缩算法 
      *  
      * @param input 
      *            输入文件 
      * @param output 
      *            输出文件 
      * @return 
      * @throws Exception 
      */  
     public static boolean convert(File input, File output) throws Exception {  
         // 输入  
         BufferedImage inputImage = ImageIO.read(input);  
   
         // 转换  
         int width = inputImage.getWidth();  
         int height = inputImage.getHeight();  
   
         RenderedImage im = (RenderedImage) convert(width, height, inputImage);  
         String outputFilename = output.getName();  
         String format = outputFilename.substring(outputFilename  
                 .lastIndexOf('.') + 1);  
         // 输出  
         return ImageIO.write(im, format, output);  
     }  
   
     /** 
      * 缩放图片 
      *  
      * @param width 
      *            输出宽度 
      * @param height 
      *            输出高度 
      * @param input 
      *            输入文件 
      * @param output 
      *            输出文件 
      * @return 
      * @throws Exception 
      */  
     public static boolean convert(int width, int height, File input, File output)  
             throws Exception {  
         // 输入  
         BufferedImage inputImage = ImageIO.read(input);  
         // 转换  
         RenderedImage im = (RenderedImage) convert(width, height, inputImage);  
         String outputFilename = output.getName();  
         String format = outputFilename.substring(outputFilename  
                 .lastIndexOf('.') + 1);  
         // 输出  
         return ImageIO.write(im, format, output);  
     }  
   
     /** 
      * 缩放图片 
      *  
      * @param width 
      *            输出宽度 
      * @param height 
      *            输出高度 
      * @param input 
      *            输入路径 
      * @param output 
      *            输出路径 
      * @return 
      * @throws Exception 
      */  
     public static boolean convert(int width, int height, String inputPath,  
             String outputPath) throws Exception {  
         return convert(width, height, new File(inputPath), new File(outputPath));  
     }  
   
     /** 
      * 转换 
      *  
      * @param width 
      *            输出宽度 
      * @param height 
      *            输出高度 
      * @param input 
      *            BufferedImage 
      * @return BufferedImage 
      * @throws Exception 
      */  
     private static BufferedImage convert(int width, int height,  
             BufferedImage input) throws Exception {  
         // 初始化输出图片  
         BufferedImage output = new BufferedImage(width, height,  
                 BufferedImage.TYPE_INT_RGB);  
   
         // 重新绘图  
         Image image = input.getScaledInstance(output.getWidth(), output  
                 .getHeight(), output.getType());  
   
         output.createGraphics().drawImage(image, null, null);  
   
         return output;  
     }  
   
     /** 
      * 等比缩放图片 
      *  
      * @param width 
      *            输出宽度 
      * @param height 
      *            输出高度 
      * @param input 
      *            输入流 
      * @param output 
      *            输出流 
      * @return 
      * @throws Exception 
      */  
     public static boolean equimultipleConvert(int width, int height,  
             String input, String output) throws Exception {  
         return equimultipleConvert(width, height, new File(input), new File(  
                 output));  
     }  
   
     /** 
      * 等比缩放图片 
      *  
      * @param width 
      *            输出宽度 
      * @param height 
      *            输出高度 
      * @param input 
      *            输入流 
      * @param output 
      *            输出流 
      * @return 
      *  
      * @throws Exception 
      */  
     public static boolean equimultipleConvert(int width, int height,  
             File input, File output) throws Exception {  
         // 输入  
         BufferedImage image = ImageIO.read(input);  
   
         // 重新核算尺寸  
         if (image.getWidth() > 0 && image.getHeight() > 0) {  
             if ((image.getWidth() / image.getHeight()) >= (width / height)) {  
                 if (image.getWidth() > width) {  
                     height = (image.getHeight() * width) / image.getWidth();  
                 } else {  
                     width = image.getWidth();  
                     height = image.getHeight();  
                 }  
             } else {  
                 if (image.getHeight() > height) {  
                     width = (image.getWidth() * height) / image.getHeight();  
                 } else {  
                     width = image.getWidth();  
                     height = image.getHeight();  
                 }  
             }  
         }  
   
         // 转换 输出  
         return convert(width, height, input, output);  
     }  
 }  

给出一个简单的测试类：

    import org.junit.Test;  
      
   /** 
    *  
    * @author 梁栋 
    * @version 0 
    * @since 0 
    */  
  public class ImageUtilsTest {  
     
       /** 
        * Test method for 
        * {@link org.zlex.common.image.ImageUtils#main(java.lang.String[])}. 
        */  
       @Test  
       public void test() throws Exception {  
           System.out.println(ImageUtils.convert(1650, 1024, "c:\\png",  
                   "c:\\png.jpg"));  
           System.out.println(ImageUtils.convert(400, 300, "c:\\jpg",  
                   "c:\\jpg.jpg"));  
          System.out.println(ImageUtils.convert(400, 300, "c:\\jpg",  
                   "c:\\jpg.png"));  
           System.out.println(ImageUtils.convert(50, 50, "c:\\jpg",  
                   "c:\\jpg.gif"));  
           System.out.println(ImageUtils.convert(40, 30, "c:\\bmp",  
                   "c:\\bmp.gif"));  
           System.out.println(ImageUtils  
                   .convert(40, 30, "c:\\bmp", "c:\\jpeg"));  
           System.out.println(ImageUtils.equimultipleConvert(1600, 1400, new File(  
                   "c:\\bmp"), new File("c:\\1Equimultiple.jpeg")));  
     
       }  
     
   }  

原文地址：http://snowolf.iteye.com/blog/250517