jpg没有被ImageIO.write覆盖（）

Question

我做了下面的例子，我找不出它为什么不起作用。

• 我的检查都不是返回false，
• 我有读写权限，
• 的ImageIO的响应，它实际上已经覆盖图像，
• 没有异常抛出...

但图像在磁盘上仍然没有改变。

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

import javax.imageio.ImageIO; 
import javax.swing.JFileChooser; 
import javax.swing.filechooser.FileNameExtensionFilter; 

public class example 
{ 
    public static void main(String[] args) 
     { 
      try 
       { 
        // load a jpg file 
        File imageFile = getFile(); 

        // Make a Buffered Image from it 
        BufferedImage img = ImageIO.read(imageFile); 

        // for every pixel in the image 
        for (int x = 0; x < img.getWidth(); x++) 
         for (int y = 0; y < img.getHeight(); y++) 
          // check if the RGB integer is an odd number 
          if (img.getRGB(x, y) % 2 != 0) 
           // make it an even number if it is odd (the OCD god demands it!) 
           img.setRGB(x, y, img.getRGB(x, y) - 1); 

        // Write the OCD friendly version to the file 
        System.out.println("Was overwritten: " + ImageIO.write(img, "jpg", imageFile)); 
        System.out.println(); 

        // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

        // Select the same file again 
        imageFile = getFile(); 

        // Make the bufferedImage from it 
        img = ImageIO.read(imageFile); 

        // for every pixel in the image 
        for (int x = 0; x < img.getWidth(); x++) 
         for (int y = 0; y < img.getHeight(); y++) 
          // check if the RGB integer is an odd number 
          if (img.getRGB(x, y) % 2 != 0) 
           { 
            // Report the failing 
            System.out.println("It didn't work :("); 
            // Stop the loop 
            x = img.getWidth(); 
            y = img.getHeight(); 
           } 
       } 
      catch (Exception e) 
       { 
        e.printStackTrace(); 
       } 
     } 

    public static File getFile() 
     { 
      // set up a file chooser that only accepts jpgs 
      JFileChooser chooser = new JFileChooser(); 
      chooser.setFileFilter(new FileNameExtensionFilter("JPG Images only", "jpg")); 

      // This will represent our loaded file 
      File imageFile = null; 

      // Select a file 
      chooser.showOpenDialog(null); 
      imageFile = chooser.getSelectedFile(); 

      // Check we can do stuff to this file 
      System.out.println("Exists: " + imageFile.exists()); 
      System.out.println("Can Read: " + imageFile.canRead()); 
      System.out.println("Can Write: " + imageFile.canWrite()); 
      System.out.println(); 

      return imageFile; 
     } 
} 

Answer 1

它被覆盖，你就是不与你的
眼睛检测视觉。那是因为你刚刚通过1

for (int x = 0; x < img.getWidth(); x++) 
    for (int y = 0; y < img.getHeight(); y++) 
     // check if the RGB integer is an odd number 
     if (img.getRGB(x, y) % 2 != 0) 
      // make it an even number if it is odd (the OCD god demands it!) 
      img.setRGB(x, y, 0); /// A /// 

改变这一行/// A ///，我确实改变了RGB值，你会看到它被覆盖。

当然，这也取决于你正在测试的图片。
如果img.getRGB(x, y)永远不会是奇数，img.setRGB永远不会执行。