详解Java中使用ImageIO类对图片进行压缩的方法

package cn.com.images;  import java.awt.Graphics; import java.awt.Image; import java.awt.image.BufferedImage; import java.io.File; import java.io.IOException; import java.math.BigDecimal; import java.math.MathContext; import java.util.ArrayList;  import javax.imageio.ImageIO;  /***  * 对图片进行操作  *  * @author chenzheng_java  * @since 2011/7/29  *  */ public class ImageHelper {    private static ImageHelper imageHelper = null;    public static ImageHelper getImageHelper() {     if (imageHelper == null) {       imageHelper = new ImageHelper();     }     return imageHelper;   }    /***    * 按指定的比例缩放图片    *    * @param sourceImagePath    *      源地址    * @param destinationPath    *      改变大小后图片的地址    * @param scale    *      缩放比例，如1.2    */   public static void scaleImage(String sourceImagePath,       String destinationPath, double scale,String format) {      File file = new File(sourceImagePath);     BufferedImage bufferedImage;     try {       bufferedImage = ImageIO.read(file);       int width = bufferedImage.getWidth();       int height = bufferedImage.getHeight();        width = parseDoubleToInt(width * scale);       height = parseDoubleToInt(height * scale);        Image image = bufferedImage.getScaledInstance(width, height,           Image.SCALE_SMOOTH);       BufferedImage outputImage = new BufferedImage(width, height,           BufferedImage.TYPE_INT_RGB);       Graphics graphics = outputImage.getGraphics();       graphics.drawImage(image, 0, 0, null);       graphics.dispose();        ImageIO.write(outputImage, format, new File(destinationPath));     } catch (IOException e) {       System.out.println("scaleImage方法压缩图片时出错了");       e.printStackTrace();     }    }    /***    * 将图片缩放到指定的高度或者宽度    * @param sourceImagePath 图片源地址    * @param destinationPath 压缩完图片的地址    * @param width 缩放后的宽度    * @param height 缩放后的高度    * @param auto 是否自动保持图片的原高宽比例    * @param format 图图片格式 例如 jpg    */   public static void scaleImageWithParams(String sourceImagePath,       String destinationPath, int width, int height, boolean auto,String format) {          try {     File file = new File(sourceImagePath);     BufferedImage bufferedImage = null;     bufferedImage = ImageIO.read(file);       if (auto) {         ArrayList<Integer> paramsArrayList = getAutoWidthAndHeight(bufferedImage,width,height);         width = paramsArrayList.get(0);         height = paramsArrayList.get(1);         System.out.println("自动调整比例，width="+width+" height="+height);       }          Image image = bufferedImage.getScaledInstance(width, height,         Image.SCALE_DEFAULT);     BufferedImage outputImage = new BufferedImage(width, height,         BufferedImage.TYPE_INT_RGB);     Graphics graphics = outputImage.getGraphics();     graphics.drawImage(image, 0, 0, null);     graphics.dispose();     ImageIO.write(outputImage, format, new File(destinationPath));     } catch (Exception e) {       System.out.println("scaleImageWithParams方法压缩图片时出错了");       e.printStackTrace();     }             }    /**    * 将double类型的数据转换为int，四舍五入原则    *    * @param sourceDouble    * @return    */   private static int parseDoubleToInt(double sourceDouble) {     int result = 0;     result = (int) sourceDouble;     return result;   }      /***    *    * @param bufferedImage 要缩放的图片对象    * @param width_scale 要缩放到的宽度    * @param height_scale 要缩放到的高度    * @return 一个集合，第一个元素为宽度，第二个元素为高度    */   private static ArrayList<Integer> getAutoWidthAndHeight(BufferedImage bufferedImage,int width_scale,int height_scale){     ArrayList<Integer> arrayList = new ArrayList<Integer>();     int width = bufferedImage.getWidth();     int height = bufferedImage.getHeight();     double scale_w =getDot2Decimal( width_scale,width);          System.out.println("getAutoWidthAndHeight width="+width + "scale_w="+scale_w);     double scale_h = getDot2Decimal(height_scale,height);     if (scale_w<scale_h) {       arrayList.add(parseDoubleToInt(scale_w*width));       arrayList.add(parseDoubleToInt(scale_w*height));     }     else {       arrayList.add(parseDoubleToInt(scale_h*width));       arrayList.add(parseDoubleToInt(scale_h*height));     }     return arrayList;        }         /***    * 返回两个数a/b的小数点后三位的表示    * @param a    * @param b    * @return    */   public static double getDot2Decimal(int a,int b){          BigDecimal bigDecimal_1 = new BigDecimal(a);     BigDecimal bigDecimal_2 = new BigDecimal(b);     BigDecimal bigDecimal_result = bigDecimal_1.divide(bigDecimal_2,new MathContext(4));     Double double1 = new Double(bigDecimal_result.toString());     System.out.println("相除后的double为："+double1);     return double1;   }  }