java 图像压缩

import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.color.ColorSpace;
import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.awt.image.ColorConvertOp;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.util.Base64;

import javax.imageio.ImageIO;

public class Program {

    public static void main(String[] args) throws Exception {
        int maxWidth = 800;
        int maxHeight = 600;
        BufferedImage image = ImageIO.read(new File("E:\\Desktop\\IMG20200322201448.jpg"));
        image = zoomImageFromWidthAndHeight(image,maxWidth,maxHeight);
        ImageIO.write(image, "jpg", new File("E:\\Desktop\\IMG20200322201448(" + maxWidth + "x" + maxHeight + ").jpg"));
        System.out.println("OK");
    }
    
    public static BufferedImage grayImage(final BufferedImage srcImg) {
        int iw = srcImg.getWidth();
        int ih = srcImg.getHeight();
        Graphics2D srcG = srcImg.createGraphics();
        RenderingHints rhs = srcG.getRenderingHints();
 
        ColorSpace cs = ColorSpace.getInstance(ColorSpace.CS_GRAY);
        ColorConvertOp theOp = new ColorConvertOp(cs, rhs);
        BufferedImage dstImg = new BufferedImage(iw, ih,
                BufferedImage.TYPE_INT_RGB);
 
        theOp.filter(srcImg, dstImg);
        return dstImg;
    }
    
    public static BufferedImage zoomImageFromWidthAndHeight(BufferedImage bufImg, int maxWidth, int maxHeight) {
        int actualWidth = bufImg.getWidth();
        int actualHeight = bufImg.getHeight();
        
        if(((double)maxWidth*(double)actualHeight/(double)actualWidth)*(double)maxWidth 
                < ((double)maxHeight*(double)actualWidth/(double)actualHeight)*(double)maxHeight)
        {
            actualHeight = (int)((double)maxWidth * (double)actualHeight / (double)actualWidth);
            actualWidth = maxWidth;
        }
        else
        {
            actualWidth = (int)((double)maxHeight * (double)actualWidth / (double)actualHeight);
            actualHeight = maxHeight;
        }
        
        double wr = 0,hr = 0;
        Image Itemp = bufImg.getScaledInstance(actualWidth, actualHeight, bufImg.SCALE_SMOOTH);//设置缩放目标图片模板
        
        wr = actualWidth*1.0 / bufImg.getWidth();
        hr = actualHeight*1.0 / bufImg.getHeight();

        AffineTransformOp ato = new AffineTransformOp(AffineTransform.getScaleInstance(wr, hr), null);
        Itemp = ato.filter(bufImg, null);
        return (BufferedImage) Itemp;
    }
    
}