项目中有时候需要对图片进行DPI、合并、拼接等的处理：

package com.snow.web.a_test;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import javax.imageio.ImageIO;import com.sun.image.codec.jpeg.JPEGCodec;import com.sun.image.codec.jpeg.JPEGEncodeParam;import com.sun.image.codec.jpeg.JPEGImageEncoder;public class Test {        private static String path = "F:\\";        public static void main(String[] args) throws Exception {        System.out.println("=======================================");//        String path = "F:\\test.jpg";  //      File files = new File(path);  //      handleDpi(files, 300, 300); //        String path = "F:\\";          File file1 = new File(path, "1.jpg");          File file2 = new File(path, "2.png");  //        mosaicImage(file1, file2);         mergeImage(file1, file2);     }    /**      * 改变图片DPI      *      * @param file      * @param xDensity      * @param yDensity      * @throws ImageReadException      */      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();          }      }     /**     * 图片拼接     * @param file1 左边     * @param file2    右边     * @throws IOException     */    public static void mosaicImage(File file1, File file2) throws IOException {                BufferedImage image1 = ImageIO.read(file1);          BufferedImage image2 = ImageIO.read(file2);            BufferedImage combined = new BufferedImage(image1.getWidth() * 2, image1.getHeight(), BufferedImage.TYPE_INT_RGB);            // paint both images, preserving the alpha channels          Graphics g = combined.getGraphics();          g.drawImage(image1, 0, 0, null);          g.drawImage(image2, image1.getWidth(), 0, null);                    // Save as new image          ImageIO.write(combined, "JPG", new File(path, "3.jpg"));      }      /**     * 图片合并     * @param file1 左边     * @param file2    右边     * @throws IOException     */    public static void mergeImage(File file1, File file2) throws IOException {                BufferedImage image1 = ImageIO.read(file1);          BufferedImage image2 = ImageIO.read(file2);            BufferedImage combined = new BufferedImage(image1.getWidth(), image1.getHeight(), BufferedImage.TYPE_INT_RGB);            // paint both images, preserving the alpha channels          Graphics g = combined.getGraphics();          System.out.println(image2.getData());        g.drawImage(image1, 0, 0, null);          g.drawImage(image2, 0, 0, image1.getWidth(), image1.getHeight(), null);                    // Save as new image          ImageIO.write(combined, "JPG", new File(path, "4.jpg"));      }      }