java 按比例缩小图片 按照宽度或者高度 缩小图片

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import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
public class PicUtils {
private
String minFile;
private
String maxFile;
private int width;
private int height;
private BufferedImage img;
private String ext;
public static void main(String[] args) {
File[] files = new File("D:\PitStop\sjpg\3JPG").listFiles();
for(int i=files.length-1;i>=0;i--){
System.out.println(files.length+"-"+i+","+files[i]);
if(files[i].getName().indexOf("jpg")!=-1){
new PicUtils(files[i].toString(),"D:\images\max","D:\images\min",0.3f,180);
}
}
}
//缩放图片工具的构造函数
public PicUtils(String srcFile,String max,String min,double maxf,int minpt){
try {
//得到最后一个.的位置
int index = srcFile.lastIndexOf(".");
//获取被缩放的图片的格式
this.ext = srcFile.substring(index + 1);
//获取目标路径(和原始图片路径相同,在文件名后添加了一个_s)
String name = new File(srcFile).getName();
name = name.replaceAll("_1.jpg",".jpg");
this.maxFile = max+"/"+name;
this.minFile = min+"/"+name;
//读取图片,返回一个BufferedImage对象
this.img = ImageIO.read(new File(srcFile));
//获取图片的长和宽
this.width = img.getWidth();
this.height = img.getHeight();
zoomByScale(maxf);
zoomBySize(minpt);
}catch (Exception e){
e.printStackTrace();
}
}
/**
* 按比例对图片进行缩放.
* @param scale 缩放比例
* @throws IOException
*/
public void zoomByScale(double scale) throws IOException {
if(!new File(maxFile).exists()){
//获取缩放后的长和宽
int _width = (int) (scale * width);
int _height = (int) (scale * height);
//获取缩放后的Image对象
Image _img = img.getScaledInstance(_width, _height, Image.SCALE_DEFAULT);
//新建一个和Image对象相同大小的画布
BufferedImage image = new BufferedImage(_width, _height, BufferedImage.TYPE_INT_RGB);
//获取画笔
Graphics2D graphics = image.createGraphics();
//将Image对象画在画布上,最后一个参数,ImageObserver:接收有关 Image 信息通知的异步更新接口,没用到直接传空
graphics.drawImage(_img, 0, 0, null);
//释放资源
graphics.dispose();
//使用ImageIO的方法进行输出,记得关闭资源
OutputStream out = new FileOutputStream(new File(maxFile));
ImageIO.write(image, ext, out);
out.close();
}
}
/**
* 指定长和宽对图片进行缩放
* @throws IOException
*/
public void zoomBySize(int w) throws IOException {
if(!new File(minFile).exists()) {
int tempw = 0;
int temph = 0;
if(this.width>this.height){
tempw = w;
temph =this.height* w/this.width;
}else{
tempw = w*this.width/this.height;
temph =w;
}
//与按比例缩放的不同只在于,不需要获取新的长和宽,其余相同.
Image _img = img.getScaledInstance(tempw, temph, Image.SCALE_DEFAULT);
BufferedImage image = new BufferedImage(tempw, temph, BufferedImage.TYPE_INT_RGB);
Graphics2D graphics = image.createGraphics();
graphics.drawImage(_img, 0, 0, null);
graphics.dispose();
OutputStream out = new FileOutputStream(new File(minFile));
ImageIO.write(image, ext, out);
out.close();
}
}
}