java 如何将像素转换为灰度？
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How to convert pixels to gray scale?
提问by Little Child
Ok, I am using Processingwhich allows me to access pixels of any image as int[]. What I now want to do is to convert the image to gray-scale. Each pixel has a structure as shown below:
好的，我正在使用Processing它允许我将任何图像的像素作为int[]. 我现在想做的是将图像转换为灰度。每个像素具有如下所示的结构：
...........PIXEL............
[red | green | blue | alpha]
<-8--><--8---><--8--><--8-->
Now, what transformations do I need to apply to individual RGB values to make the image gray-scale ??
What I mean is, how much do I add / subtract to make the image gray-scale ?
现在，我需要对各个 RGB 值应用哪些转换才能使图像灰度化？
我的意思是，我要加/减多少才能使图像灰度？
Update
更新
I found a few methods here: http://www.johndcook.com/blog/2009/08/24/algorithms-convert-color-grayscale/
我在这里找到了一些方法：http: //www.johndcook.com/blog/2009/08/24/algorithms-convert-color-grayscale/
回答by Renan
For each pixel, the value for the red, green and blue channels should be their averages. Like this:
对于每个像素，红色、绿色和蓝色通道的值应该是它们的平均值。像这样：
int red = pixel.R;
int green = pixel.G;
int blue = pixel.B;
pixel.R = pixel.G = pixel.B = (red + green + blue) / 3;
Since in your case the pixel colors seem to be stored in an array rather than in properties, your code could end up looking like:
由于在您的情况下，像素颜色似乎存储在数组中而不是属性中，因此您的代码最终可能如下所示：
int red = pixel[0];
int green = pixel[1];
int blue = pixel[2];
pixel[0] = pixel[1] = pixel[2] = (red + green + blue) / 3;
The general idea is that when you have a gray scale image, each pixel's color measures only the intensity of light at that point - and the way we perceive that is the average of the intensity for each color channel.
一般的想法是，当您拥有灰度图像时，每个像素的颜色仅测量该点的光强度 - 我们感知的方式是每个颜色通道强度的平均值。
回答by user2468700
The following code loads an image and cycle through its pixels, changing the saturationto zero and keeping the same hueand brightnessvalues.
以下代码加载图像并循环遍历其像素，将饱和度更改为零并保持相同的色调和亮度值。
PImage img;
void setup () {
colorMode(HSB, 100);
img = loadImage ("img.png");
size(img.width,img.height);
color sat = color (0,0,0);
img.loadPixels();
for (int i = 0; i < width * height; i++) {
img.pixels[i]=color (hue(img.pixels[i]), sat, brightness(img.pixels[i]));
}
img.updatePixels();
image(img,0,0);
}
