切图代码：

import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Iterator;

import javax.imageio.ImageIO;
import javax.imageio.ImageReadParam;
import javax.imageio.ImageReader;
import javax.imageio.stream.ImageInputStream;

/**
 * 图片剪裁
 * @param x 距离左上角的x轴距离
 * @param y 距离左上角的y轴距离
 * @param width 宽度
 * @param height 高度
 * @param sourcePath 图片源
 * @param descpath 目标位置
 */ 
public class printt {
    public static void imageCut(int x, int y, int width, int height, String sourcePath, String descpath) {
        FileInputStream is = null;
        ImageInputStream iis = null;
        try {
            is = new FileInputStream(sourcePath);
            String fileSuffix = sourcePath.substring(sourcePath.lastIndexOf(".") + 1);
            Iterator<ImageReader> it = ImageIO.getImageReadersByFormatName(fileSuffix);
            ImageReader reader = it.next();
            iis = ImageIO.createImageInputStream(is);
            reader.setInput(iis, true);
            ImageReadParam param = reader.getDefaultReadParam();
            Rectangle rect = new Rectangle(x, y, width, height);
            param.setSourceRegion(rect);
            BufferedImage bi = reader.read(0, param);
            ImageIO.write(bi, fileSuffix, new File(descpath));
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                is = null;
            }
            if (iis != null) {
                try {
                    iis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                iis = null;
            }
        }
    }

    public static void main(String args[]) {
        imageCut(500,300,300,500,"f://12.jpg","f://13.jpg");
    }
}

示例图片：

切图结果：

注意：如果不关闭流的话可能会影响其他代码对图片的操作，尤其是删除等操作
 

判断是否是纯色图片的代码，稍微改一下可以用来判断是不是彩色图片：

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

/**
 * 判断是否为纯色
 * @param imgPath 图片源
 * @param percent 纯色百分比，即大于此百分比为同一种颜色则判定为纯色,范围[0-1]
 * @return
 * @throws IOException
 */ 
public class printt {
    public static boolean isSimpleColorImg(String imgPath, float percent) throws IOException {
        BufferedImage src = ImageIO.read(new File(imgPath));
        int height = src.getHeight();
        int width = src.getWidth();
        int count = 0, pixTemp = 0, pixel = 0;
        for (int i = 0; i < width; i++) {
            for (int j = 0; j < height; j++) {
                pixel = src.getRGB(i, j);
                if (pixel == pixTemp) // 如果上一个像素点和这个像素点颜色一样的话，就判定为同一种颜色
                    count++;
                else
                    count = 0;
                if ((float) count / (height * width) >= percent) // 如果连续相同的像素点大于设定的百分比的话，就判定为是纯色的图片
                    return true;
                pixTemp = pixel;
            }
        }
        return false;
    }

    public static void main(String args[]) throws IOException {
        System.out.println(isSimpleColorImg("f://14.jpg", 0.99f));
    }
}

示例图片：

运行代码结果为：true
 
代码来自：

https://www.jb51.net/article/121231.htm