java中压缩图片的代码辅助类

 

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;
	}

}