在JAVA中保存图像后，RGB值无法正确更改 [英] RGB value not change correctly after saving image in JAVA

问题描述

我正在尝试将图像类型JPG / JPEG读取到 BufferedImage ，更改像素（0,0）的RGB值

图像文件： http://i.upanh.com/rcfutp

但它没有'正常工作

这是我试过的
阅读图片

I'm trying to read an Image type JPG/JPEG to BufferedImage , change RGB value of pixel (0,0)
Image file : http://i.upanh.com/rcfutp
but it didn't work correctly
Here is what i've try
Read image

public BufferedImage readImage1(String path)
    {
        BufferedImage _image = null;
        BufferedImage copy = null;
        try {
            _image = ImageIO.read(new File(path));
            copy = new BufferedImage(_image.getWidth(), _image.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
            copy.getGraphics().drawImage(_image, 0, 0, null);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return copy;
    }

写入图片

public void writeImage1(String path,BufferedImage _image)
    {
        try {
            ImageIO.write(_image, "jpg", new File(path));
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

客户代码

    BufferedImage image = readImage1("E:/2.jpg");
System.out.print((image.getRGB(0, 0))&0xFFFFFF);
System.out.print("-");
image.setRGB(0, 0, 0x00000F);
System.out.print((image.getRGB(0, 0))&0xFFFFFF);
System.out.print("-");
writeImage1("E:/3.jpg", image);     
image = readImage1("E:/3.jpg");
System.out.print((image.getRGB(0, 0))&0xFFFFFF);

System.out.print return

System.out.print return

7736127-15-5439516

我希望它是 7736127-15-15 ，但它返回 7736127-15-15-5439516
请帮我纠正，非常感谢很多人

I hope it was 7736127-15-15,but it return 7736127-15-5439516 please help me to correct ,thank you very much guy

推荐答案

这是不可能的，因为jpg如何压缩数据，当你对图像的每个像素进行操作时，它是你正在操作的图像的解压缩版本，jpg格式是一种有损压缩格式。压缩图像然后解压缩它将不会产生原始图像。这就是像素值不同的原因。

This is not possible because of how jpg compresses data, when you are operating on every pixel of the image it is the unpacked version of the image you are operating on, the jpg format is a lossy compression format. Compressing an image then decompressing it will not yield the original image. This is why pixel values are different.

这可以在下图中清楚地看到。注意右边的线，右边是jpg压缩，然后是左侧的解压缩。

This can be clearly seen in the following image. Notice the "lines" to the right, the right side is the jpg compression then decompression of the left side.

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferByte;
import java.beans.Transient;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;

@SuppressWarnings("serial")
public class ImageTest extends JPanel {

    private BufferedImage image;
    private BufferedImage saved;

    public ImageTest(int w, int h) {
        image = new BufferedImage(w, h, BufferedImage.TYPE_3BYTE_BGR);
        randomizeImage(image);
        saveAndLoadImage();
        saveResultToLossLess();
    }

    private void saveResultToLossLess() {
        BufferedImage result = new BufferedImage(image.getWidth() * 2,
                image.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
        result.getGraphics().drawImage(image, 0, 0, null);
        result.getGraphics().drawImage(saved, image.getWidth(), 0, null);
        try {
            ImageIO.write(result, "png", new File("comparison.png"));
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    private void randomizeImage(BufferedImage image) {
        // Draw a blue gradient, note that in the array below
        // pixels[i] = blue, pixels[i+1] = green, pixels[i+2] = red
        byte[] pixels = ((DataBufferByte) image.getRaster().getDataBuffer())
                .getData();
        for (int i = 0; i < pixels.length; i += 3) {
            pixels[i] = (byte) (255.0 * i / pixels.length);
            pixels[i + 1] = (byte) (128.0 * i / pixels.length);
            pixels[i + 2] = (byte) (64.0 * i / pixels.length);
        }
    }

    private void saveAndLoadImage() {
        try {
            ImageIO.write(image, "jpg", new File("image.jpg"));
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        try {
            saved = ImageIO.read(new File("image.jpg"));
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(image, 0, 0, null);
        if (saved != null)
            g.drawImage(saved, image.getWidth(), 0, null);
    }

    @Override
    @Transient
    public Dimension getPreferredSize() {
        return new Dimension(image.getWidth() * 2, image.getHeight());
    }

    public static void main(String[] args) {
        ImageTest test = new ImageTest(600, 600);
        JFrame frame = new JFrame();
        frame.getContentPane().add(test);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }
}

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