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; 
  } 
 
}