当我设置setRGB的值时，getRGB返回不同的值。 为什么？

Question

Why here I setRGB () with three RGB colors (125, 126, 127), but when getRGB it returns another value that is (125, 126, 128). For (122, 126, 127), it returns true (122, 126, 127). Why? And: Input: image.setRGB (0, 0, 5072962) // 77 ----- 104 ----- 66 ------- 5072962 Output: 78 ------ 104 ------ 69 ------- 5138501 (With rgb = (red << 16) | (green << 8) | blue;)

My code:

// 77-------104-------66------5072962

final static int rgb = 5072962;

public static void main(String[] args) {

    BufferedImage image = new BufferedImage(1, 1, BufferedImage.TYPE_INT_RGB);

    //image.setRGB(0, 0, 5072962);
    Color c = new Color(125, 126, 127);
    image.setRGB(0, 0, c.getRGB());

    File outputFile = new File("123.jpg");
    try {
        ImageIO.write(image, "jpg", outputFile);
        File f = new File("123.jpg");
        BufferedImage bi = ImageIO.read(f);
        for (int h = 0; h < 1; h++) {
            for (int w = 0; w < 1; w++) {
                int pixel = bi.getRGB(w, h);
                Color c2 = new Color(pixel);

                int red = c2.getRed();
                int green = c2.getGreen();
                int blue = c2.getBlue();

                int rgb = (red << 16) | (green << 8) | blue;
                System.out.printf("%-8d%-8d%-8d%-8d", red, green, blue, rgb);
                System.out.println("");
            }
        }
    } catch (IOException ex) {
        System.out.println("Error output File image!");
    }

}

Answer 1

At first, Did you Know about Image file formats ? I have the same problem before in similar case. I would like to suggest you the following.

When you use jpg for the image write operation to store in your storage, RGB values changes slightly because jpg format is a lossy compressed file format. This compression allows you for the optimal space to store the file but it doesn't store the information of RGB values you want.

So, If file format is not a big issue for you , then simply use PNG format. PNG format is a lossless compression file format so that you can retrieve RGB values you have set before in the program.

Hope it might help you.