JAVA生成缩略图

package com.my.image;

import javax.imageio.ImageIO;

import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.WritableRaster;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

public class ImageUtils {

public static void main(String[] args) throws FileNotFoundException, IOException { 
     File picture = new File("C:/Users/Administrator/Desktop/buys/1.png");
        BufferedImage sourceImg =ImageIO.read(new FileInputStream(picture));
        System.out.println(picture.getPath().substring(picture.getPath().lastIndexOf(".")));
        System.out.println(picture.length()/1024.0); 
        System.out.println("width:"+sourceImg.getWidth()+"px"); 
        System.out.println("height:"+sourceImg.getHeight()+"px");
        System.out.println(picture.getName().substring(0,picture.getName().lastIndexOf("."))+"_pic"+picture.getName().substring(picture.getName().lastIndexOf(".")));
        try {
        String[] rets = ImageUtils.saveImage("C:/Users/Administrator/Desktop/buys/1_1.png","C:/Users/Administrator/Desktop/buys/1_3.png", 200);
        System.out.println("code:"+rets[0]+",Msg:"+rets[1]);
} catch (Exception e) {
e.printStackTrace();
}

//System.out.println(Double.parseDouble(String.format("%.1f",1000d/600)));

}

/**
  * 生成文件
  * @param image 源文件流
  * @param newWidth 缩小宽度
  * @param newHeigh 缩小高度
  * @return
  */
public static BufferedImage resize(BufferedImage image, int newWidth,int newHeigh) {
int type = image.getType();
BufferedImage newImage = null;
double sx = (double) newWidth / image.getWidth();
double sy = (double) newHeigh / image.getHeight();
if (type == BufferedImage.TYPE_CUSTOM) {
ColorModel cm = image.getColorModel();
WritableRaster raster = cm.createCompatibleWritableRaster(newWidth,newHeigh);
boolean alphaPremultiplied = cm.isAlphaPremultiplied();
newImage = new BufferedImage(cm, raster, alphaPremultiplied, null);
} else {
newImage = new BufferedImage(newWidth, newHeigh, type);
Graphics2D g = newImage.createGraphics();
g.setRenderingHint(RenderingHints.KEY_RENDERING,RenderingHints.VALUE_RENDER_QUALITY);
g.drawRenderedImage(image, AffineTransform.getScaleInstance(sx, sy));
g.dispose();
}

return newImage;
}

/**
  * 保存缩略图
  * @param fromFilePath 源文件路径
  * @param saveToFilePath 生成新文件路径
  * @param size 限制尺寸
  * @return
  * @throws Exception
  */
public static String[] saveImage(String fromFilePath, String saveToFilePath,int size) throws Exception {
String[] rets = new String[2];
BufferedImage srcImage;
String imgType = "JPEG";
double maxLeng = 0d;
double ratio = 0;
if (fromFilePath.toLowerCase().endsWith(".png")) {
imgType = "PNG";
}
else if (fromFilePath.toLowerCase().endsWith(".jpg")) {
imgType = "JPEG";
}
else if (fromFilePath.toLowerCase().endsWith(".bmp")) {
imgType = "BMP";
}
else if (fromFilePath.toLowerCase().endsWith(".gif")) {
imgType = "GIF";
} else {
rets[0]="0";
rets[1]="不支持此图片格式！";
return rets;
}
File saveFile = new File(saveToFilePath);
File fromFile = new File(fromFilePath);
srcImage = ImageIO.read(fromFile);
int fileSize = 2048;
if (fromFile.length()/1024.0>fileSize) {
rets[0]="0";
rets[1]="图片过大，请上传不大于2M的图片！";
return rets;
}
double width = (double)srcImage.getWidth();
double height = (double)srcImage.getHeight();
if (width > 0 || height > 0) {
//计算比例
if (width > height) {
maxLeng = width;
ratio = maxLeng/size;
} else {
maxLeng = height;
ratio = maxLeng/size;
}
if (maxLeng > size) {
int newWidth = (int) (width/ratio);
int newHeight = (int) (height/ratio);
srcImage = resize(srcImage, newWidth, newHeight);
}
}
boolean isSuccess = ImageIO.write(srcImage, imgType, saveFile);
if (isSuccess) {
rets[0]="1";
rets[1]="上传成功！";
return rets;
}else {
rets[0]="0";
rets[1]="上传发生错误！";
return rets;
}
}

}

以上代码复制可用