c ++和opencv获取和设置像素颜色为Mat [英] c++ and opencv get and set pixel color to Mat

问题描述

我想为某个像素设置一个新的颜色值到cv :: Mat图像中我的代码如下：

  Mat image = img; 
 for（int y = 0; y< img.rows; y ++）
 {
 for（int x = 0; x  {
 Vec3b color = image.at< Vec3b>（Point（x，y））; 
 if（color [0]> 150&& color [1]> 150&& color [2]> 150）
 {
 color [0] = 0; 
 color [1] = 0; 
 color [2] = 0; 
 cout<< Pixel> 200：< x < ，< y < endl; 
} 
 else 
 {
 color.val [0] = 255; 
 color.val [1] = 255; 
 color.val [2] = 255; 
} 
} 
 imwrite（../ images / imgopti+ to_string（i）+。tiff，image）; 
  

看起来在输出中获得了良好的像素）相关像素不被修改。我已经尝试使用color.val [0] ..我仍然无法弄清楚为什么输出图像中的像素颜色不会改变。
感谢

解决方案

除了将新的像素值复制回图像之外，
$ b

此行将像素的副本复制到局部变量中：

  Vec3b color = image .at Vec3b（Point（x，y））; 
  

因此，在根据需要更改 color ，只需如下设置：

  image.at< Vec3b>（Point（x，y））= color; 
  

所以，完整的，像这样：

  Mat image = img; 
 for（int y = 0; y< img.rows; y ++）
 {
 for（int x = 0; x  {
 //获取像素
 Vec3b color = image.at< Vec3b>（Point（x，y））; 
 
 // ...对颜色执行某些操作.... 
 
 //设置像素
 image.at< Vec3b>（Point（x，y ））= color; 
} 
} 
  

I'm trying to set a new color value to some pixel into a cv::Mat image my code is below:

    Mat image = img;
    for(int y=0;y<img.rows;y++)
    {
        for(int x=0;x<img.cols;x++)
        {
        Vec3b color = image.at<Vec3b>(Point(x,y));
        if(color[0] > 150 && color[1] > 150 && color[2] > 150)
        {
            color[0] = 0;
            color[1] = 0;
            color[2] = 0;
            cout << "Pixel >200 :" << x << "," << y << endl;
        }
        else
        {
            color.val[0] = 255;
            color.val[1] = 255;
            color.val[2] = 255;
        }
    }
    imwrite("../images/imgopti"+to_string(i)+".tiff",image);

It seems to get the good pixel in output (with cout) however in the output image (with imwrite) the pixel concerned aren't modified. I have already tried using color.val[0].. I still can't figure out why the pixel colors in the output image dont change. thanks

解决方案

You did everything except copy the new pixel value back to the image.

This line takes a copy of the pixel into a local variable:

Vec3b color = image.at<Vec3b>(Point(x,y));

So, after changing color as you require, just set it back like this:

image.at<Vec3b>(Point(x,y)) = color;

So, in full, something like this:

Mat image = img;
for(int y=0;y<img.rows;y++)
{
    for(int x=0;x<img.cols;x++)
    {
        // get pixel
        Vec3b color = image.at<Vec3b>(Point(x,y));

        // ... do something to the color ....

        // set pixel
        image.at<Vec3b>(Point(x,y)) = color;
    }
}

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