java高质量缩放图片的示例代码

可按照比例缩放，也可以指定宽高

import com.sun.image.codec.jpeg.jpegimageencoder;
import com.sun.image.codec.jpeg.jpegcodec;
import com.sun.image.codec.jpeg.jpegencodeparam;
import javax.swing.*;
import java.io.file;
import java.io.fileoutputstream;
import java.io.ioexception;
import java.awt.*;
import java.awt.image.bufferedimage;
import java.awt.image.kernel;
import java.awt.image.convolveop;
 
public class imageutil {
   /**
   * 
   * @param originalfile 原文件
   * @param resizedfile 压缩目标文件
   * @param newwidth 压缩后的图片宽度
   * @param quality 压缩质量（0到1之间，越高质量越好）
   * @throws ioexception
   */

	public static void resize(file originalfile, file resizedfile,
			int newwidth, float quality) throws ioexception {
 
		if (quality > 1) {
			throw new illegalargumentexception(
					"quality has to be between 0 and 1");
		}
 
		imageicon ii = new imageicon(originalfile.getcanonicalpath());
		image i = ii.getimage();
		image resizedimage = null;
 
		int iwidth = i.getwidth(null);
		int iheight = i.getheight(null);
        //比例缩放
		if (iwidth > iheight) {
			resizedimage = i.getscaledinstance(newwidth, (newwidth * iheight)
					/ iwidth, image.scale_smooth);
		} else {
			resizedimage = i.getscaledinstance((newwidth * iwidth) / iheight,
					newwidth, image.scale_smooth);
		}
        //指定宽高
		image temp = new imageicon(resizedimage).getimage();
		// create the buffered image.
        bufferedimage bufferedimage = new bufferedimage(temp.getwidth(null),
				temp.getheight(null), bufferedimage.type_int_rgb);
		// copy image to buffered image.
        graphics g = bufferedimage.creategraphics();
		// clear background and paint the image.
		g.setcolor(color.white);
		g.fillrect(0, 0, temp.getwidth(null), temp.getheight(null));
		g.drawimage(temp, 0, 0, null);
		g.dispose();
 
		// soften.
		float softenfactor = 0.05f;
		float[] softenarray = { 0, softenfactor, 0, softenfactor,
				1 - (softenfactor * 4), softenfactor, 0, softenfactor, 0 };
		kernel kernel = new kernel(3, 3, softenarray);
		convolveop cop = new convolveop(kernel, convolveop.edge_no_op, null);
		bufferedimage = cop.filter(bufferedimage, null);
 
		// write the jpeg to a file.
		fileoutputstream out = new fileoutputstream(resizedfile);
 
		// encodes image as a jpeg data stream
		jpegimageencoder encoder = jpegcodec.createjpegencoder(out);
 
		jpegencodeparam param = encoder
				.getdefaultjpegencodeparam(bufferedimage);
 
		param.setquality(quality, true);
 
		encoder.setjpegencodeparam(param);
		encoder.encode(bufferedimage);
	} // example usage
 
	public static void main(string[] args) throws ioexception {
		 file originalimage = new file("c:p7.gif");
		 resize(originalimage, new file("c:p7-0.jpg"),150, 0.7f);
		 resize(originalimage, new file("c:p7-1.jpg"),150, 1f);
	}
}

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