使用java修改图片DPI详解编程语言

import com.sun.image.codec.jpeg.JPEGCodec;   
import com.sun.image.codec.jpeg.JPEGEncodeParam;   
import com.sun.image.codec.jpeg.JPEGImageEncoder;   
   
import javax.imageio.ImageIO;   
import java.awt.image.BufferedImage;   
import java.io.File;   
import java.io.FileOutputStream;   
import java.io.IOException;   
   
public class DPIHandleHelper {   
    private static int DPI = 300;   
   
    public static void main(String[] args) {   
        String path = "C://test.jpg";   
        File file = new File(path);   
        handleDpi(file, 300, 300);   
    }   
   
    /**  
     * 改变图片DPI  
     *  
     * @param file  
     * @param xDensity  
     * @param yDensity  
     */   
    public static void handleDpi(File file, int xDensity, int yDensity) {   
        try {   
            BufferedImage image = ImageIO.read(file);   
            JPEGImageEncoder jpegEncoder = JPEGCodec.createJPEGEncoder(new FileOutputStream(file));   
            JPEGEncodeParam jpegEncodeParam = jpegEncoder.getDefaultJPEGEncodeParam(image);   
            jpegEncodeParam.setDensityUnit(JPEGEncodeParam.DENSITY_UNIT_DOTS_INCH);   
            jpegEncoder.setJPEGEncodeParam(jpegEncodeParam);   
            jpegEncodeParam.setQuality(0.75f, false);   
            jpegEncodeParam.setXDensity(xDensity);   
            jpegEncodeParam.setYDensity(yDensity);   
            jpegEncoder.encode(image, jpegEncodeParam);   
            image.flush();   
        } catch (IOException e) {   
            e.printStackTrace();   
        }   
    }   
}