图片裁剪

package com.example.atlogging.controller;

import javax.imageio.ImageIO;
import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;

/*
* 图片压缩
* https://www.cnblogs.com/miskis/p/5500822.html
*/
public class UploadImg {
    String fromFileStr;
    String saveToFileStr;
    String sysimgfile;
    int width;
    int height;
    String suffix;

    /**
     * @param fromFileStr   原始图片完整路径
     * @param saveToFileStr 缩略图片保存路径
     * @param sysimgfile 处理后的图片名
     * @param suffix  处理后的图片后缀名
     * @param width  处理后的图片宽度
     * @param height  处理后的图片高度
     */
    public UploadImg(String fromFileStr, String saveToFileStr, String sysimgfile, String suffix, int width, int height) {
        this.fromFileStr = fromFileStr;
        this.saveToFileStr = saveToFileStr;
        this.sysimgfile = sysimgfile;
        this.width = width;
        this.height = height;
        this.suffix = suffix;
        File saveFilePath = new File(saveToFileStr);
        if (!saveFilePath.exists()) {
            saveFilePath.mkdirs();
        }
    }

    public boolean createThumbnail() throws Exception {
        // fileExtNmae是图片的格式 gif JPG 或png
        // String fileExtNmae="";
        File F = new File(this.fromFileStr);
        if (!F.isFile())
            throw new Exception(F
                    + " is not image file error in CreateThumbnail!");
        File ThF = new File(this.saveToFileStr, this.sysimgfile + "." + this.suffix);
        BufferedImage buffer = ImageIO.read(F);
        /*
         * 核心算法，计算图片的压缩比
         */
        int w = buffer.getWidth();
        int h = buffer.getHeight();
        double ratiox = 0.1d;
        double ratioy = 0.1d;

        ratiox = w * ratiox / this.width;
        ratioy = h * ratioy / this.height;

        if (ratiox >= 1) {
            if (ratioy < 1) {
                ratiox = this.height * 1.0 / h;
            } else {
                if (ratiox > ratioy) {
                    ratiox = this.height * 1.0 / h;
                } else {
                    ratiox = this.width * 1.0 / w;
                }
            }
        } else {
            if (ratioy < 1) {
                if (ratiox > ratioy) {
                    ratiox = this.height * 1.0 / h;
                } else {
                    ratiox = this.width * 1.0 / w;
                }
            } else {
                ratiox = this.width * 1.0 / w;
            }
        }
        /*
         * 对于图片的放大或缩小倍数计算完成，ratiox大于1，则表示放大，否则表示缩小
         */
        AffineTransformOp op = new AffineTransformOp(AffineTransform
                .getScaleInstance(ratiox, ratiox), null);
        buffer = op.filter(buffer, null);
        //从放大的图像中心截图
        buffer = buffer.getSubimage((buffer.getWidth() - this.width) / 2, (buffer.getHeight() - this.height) / 2, this.width, this.height);
        try {
            ImageIO.write(buffer, this.suffix, ThF);
        } catch (Exception ex) {
            throw new Exception(" ImageIo.write error in CreatThum.: "
                    + ex.getMessage());
        }
        return (true);
    }

    public static void main(String[] args) {
        UploadImg UI;
        boolean ss = false;
        try {
            String sysimgFile = "";//new Date().getTime() + "" + (int) (Math.random() * 100000);
            SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");//设置日期格式
            sysimgFile = df.format(new Date()) + "_8M";
            System.out.println(sysimgFile);
            UI = new UploadImg("F:/桌面temp/ys/8M.jpg",
                    "F:/桌面temp/ys", sysimgFile,
                    "jpg",
                    3024,
                    4032);
            ss = UI.createThumbnail();
            if (ss) {
                System.out.println("Success");
            } else {
                System.out.println("Error");
            }
        } catch (Exception e) {
            System.out.print(e.toString());
        }
    }
}