将大图片 转换成小图 （转）

import java.io.File;
import java.awt.image.BufferedImage;
import java.awt.Image;
import java.awt.image.AffineTransformOp;
import javax.imageio.ImageIO;
import java.awt.geom.AffineTransform;

public class ImageFormat {

   
    public String fromdir;

    public String todir;

    public String imgfile;

    public String sysimgfile;

    public ImageFormat() {

    }

    public ImageFormat(String fromdir, String todir, String imgfile,
            String sysimgfile) {

        this.fromdir = fromdir;
        this.todir = todir;
        this.imgfile = imgfile;
        this.sysimgfile = sysimgfile;

    }

    public boolean isJpg(String f) {

        boolean is = false;

        if (f.endsWith("jpg") || f.endsWith("JPG")) {

            is = true;

        } else {

            is = false;
        }
        ;
        return is;
    }

    public boolean change(int height, int width) throws Exception {

        int h = height;
        int w = width;
        //    ext是图片的格式 gif JPG 或png
        String ext = "";
        double Ratio = 0.0;
        System.out.println(width);
        File F = new File(fromdir + imgfile);
        if (!F.isFile())
            throw new Exception(F
                    + " is not image file error in CreateThumbnail!");

        if (isJpg(imgfile)) {
            ext = "jpg";
        } else {
            ext = "png";
        }
        File ThF = new File(todir, sysimgfile);

        BufferedImage Bi = ImageIO.read(F);

        Image Itemp = Bi.getScaledInstance(h, w, BufferedImage.SCALE_SMOOTH);

        if (Bi.getWidth() > w) {

            Ratio = (float) w / Bi.getWidth();

        } else {

            Ratio = 1;
        }
       

        AffineTransformOp op = new AffineTransformOp(AffineTransform.getScaleInstance(Ratio, Ratio), null);
        Itemp = op.filter(Bi, null);

        try {
            ImageIO.write((BufferedImage) Itemp, ext, ThF);
        } catch (Exception ex) {
            throw new Exception(" ImageIo.write error in CreatThum.: "
                    + ex.getMessage());
        }

        return (true);
    }

    public static void main(String arg[]) {

        String pic = "111.jpg";
        String path = "D:/";
        String newPic = "222.jpg";

        ImageFormat im = new ImageFormat(path, path, pic, newPic);

        try {
            im.change(300, 520);
        } catch (Exception e) {

            e.printStackTrace();
        }

    }
}