BufferedImage颜色意外更改 [英] BufferedImage unexpectedly changing color

问题描述

我有以下代码，该代码创建灰度BufferedImage，然后设置每个像素的随机颜色。

I have following code, which creates grayscale BufferedImage and then sets random colors of each pixel.

import java.awt.image.BufferedImage;

public class Main {

    public static void main(String[] args) {
        BufferedImage right = new BufferedImage(100, 100, BufferedImage.TYPE_BYTE_GRAY);
        int correct = 0, error = 0;
        for (int i = 0; i < right.getWidth(); i++) {
            for (int j = 0; j < right.getHeight(); j++) {
                int average = (int) (Math.random() * 255);
                int color = (0xff << 24) | (average << 16) | (average << 8) | average;
                right.setRGB(i, j, color);
                if(color != right.getRGB(i, j)) {
                    error++;
                } else {
                    correct++;
                }
            }
        }
        System.out.println(correct + ", " + error);
    }
}

在大约25-30％的像素中会出现奇怪的行为，我在此处设置颜色，然后立即设置颜色，该值与之前设置的值不同。我设置颜色的方式有误吗？

In approximately 25-30% pixels occurs weird behaviour, where I set color and right afterwards it has different value than was previously set. Am I setting colors the wrong way?

推荐答案

这是您的解决方案：禁止getRGB并使用Raster（比getRGB更快，更容易）甚至更好的DataBuffer（最快，但您必须处理编码）：

Here is your solution: ban getRGB and use the Raster (faster and easier than getRGB) or even better DataBuffer (fastest but you have to handle the encoding):

import java.awt.image.BufferedImage;

public class Main
{

public static void main(String[] args)
    {
    BufferedImage right = new BufferedImage(100, 100, BufferedImage.TYPE_BYTE_GRAY);
    int correct = 0, error = 0;
    for (int x=0 ; x < right.getWidth(); x++)
        for (int j = 0; j < right.getHeight(); j++)
            {
            int average = (int) (Math.random() * 255) ;
            right.getRaster().setSample(x, y, 0, average) ;
            if ( average != right.getRaster().getSample(x, y, 0) ) error++ ;
            else correct++;
            }
    System.out.println(correct + ", " + error);
    }
}

在您的情况下，getRGB很糟糕，因为编码是一个字节数组（8位），您必须使用getRGB操作RGB值。栅格将为您完成所有转换工作。

In your case getRGB is terrible, because the encoding is an array of byte (8 bits), and you have to manipulate RGB values with getRGB. The raster does all the work of conversion for you.

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