blocks|key|244320|text|低级方法是直接访问矩阵数据。在RGB图像(我相信OpenCV通常将其存储为BGR)中，假设您的cv::Mat变量名为frame，您可以通过以下方式获得location+(x，y)处的蓝色值(从左上角开始)：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|244321|frame.data[frame.channels()*(frame.cols*y+%2B+x)];|code-block|syntax|javascript|244322|同样，要获得B、G和R：|244323|uchar+b+=+frame.data[frame.channels()*(frame.cols*y+%2B+x)+%2B+0];++++
uchar+g+=+frame.data[frame.channels()*(frame.cols*y+%2B+x)+%2B+1];
uchar+r+=+frame.data[frame.channels()*(frame.cols*y+%2B+x)+%2B+2];|244324|请注意，此代码假定步幅等于图像的宽度。|BOLD|244325|entityMap^0|1M|5|2D|1|2F|1|0|0|0|0|0|J|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|10|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|11|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|12|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|13|8|@$9|14|A|15|B|Q]]|D|@]|E|$]]|$1|R|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|S|$]]

The low-level way would be to access the matrix data directly. In an RGB image (which I believe OpenCV typically stores as BGR), and assuming your cv::Mat variable is called <code>frame</code>, you could get the blue value at location (<code>x</code>, <code>y</code>) (from the top left) this way:

<pre><code>frame.data[frame.channels()*(frame.cols*y + x)];
</code></pre>

Likewise, to get B, G, and R:

<pre><code>uchar b = frame.data[frame.channels()*(frame.cols*y + x) + 0]; 
uchar g = frame.data[frame.channels()*(frame.cols*y + x) + 1];
uchar r = frame.data[frame.channels()*(frame.cols*y + x) + 2];
</code></pre>

Note that this code assumes the stride is equal to the width of the image.

blocks|key|244336|text|当前版本允许cv::Mat::at函数处理3+dimensions。因此，对于Mat对象m，m.at<uchar>(0,0,0)应该可以工作。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|244337|entityMap|0|LINK|mutability|MUTABLE|url|http://opencv.willowgarage.com/documentation/cpp/core_basic_structures.html#cv-mat-at^0|6|B|13|3|18|1|1A|I|L|C|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@$9|W|A|X|1|Y]]|E|$]]|$1|F|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

The current version allows the <code>cv::Mat::at</code> function to handle <a href="http://opencv.willowgarage.com/documentation/cpp/core_basic_structures.html#cv-mat-at" rel="nofollow">3 dimensions</a>. So for a <code>Mat</code> object <code>m</code>, <code>m.at&lt;uchar&gt;(0,0,0)</code> should work.

blocks|key|239384|text|尝试以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|239385|cv::Mat+image+=+...do+some+stuff...;|code-block|syntax|javascript|239386|image.at<cv::Vec3b>(y,x);给出了cv::Vec3b类型的RGB+(它可能被排序为BGR)向量|offset|length|style|CODE|239387|image.at<cv::Vec3b>(y,x)[0]+=+newval[0];
image.at<cv::Vec3b>(y,x)[1]+=+newval[1];
image.at<cv::Vec3b>(y,x)[2]+=+newval[2];|239388|entityMap^0|0|0|0|P|S|9|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]|$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|P|$]]

Try the following:

<pre><code>cv::Mat image = ...do some stuff...;
</code></pre>

<code>image.at&lt;cv::Vec3b&gt;(y,x);</code> gives you the RGB (it might be ordered as BGR) vector of type <code>cv::Vec3b</code>

<pre><code>image.at&lt;cv::Vec3b&gt;(y,x)[0] = newval[0];
image.at&lt;cv::Vec3b&gt;(y,x)[1] = newval[1];
image.at&lt;cv::Vec3b&gt;(y,x)[2] = newval[2];
</code></pre>

blocks|key|239395|text|对于有这样问题的人来说，一段代码更容易。我分享了我的代码，你可以直接使用它。请注意，OpenCV将像素存储为BGR。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|239396|cv::Mat+vImage_;+

if(src_)
{
++++cv::Vec3f+vec_;

++++for(int+i+=+0;+i+<+vHeight_;+i%2B%2B)
++++++++for(int+j+=+0;+j+<+vWidth_;+j%2B%2B)
++++++++{
++++++++++++vec_+=+cv::Vec3f((*src_)[0]/255.0,+(*src_)[1]/255.0,+(*src_)[2]/255.0);//Please+note+that+OpenCV+store+pixels+as+BGR.

++++++++++++vImage_.at<cv::Vec3f>(vHeight_-1-i,+j)+=+vec_;

++++++++++++%2B%2Bsrc_;
++++++++}
}

if(!+vImage_.data+)+//+Check+for+invalid+input
++++printf("failed+to+read+image+by+OpenCV.");
else
{
++++cv::namedWindow(+windowName_,+CV_WINDOW_AUTOSIZE);
++++cv::imshow(+windowName_,+vImage_);+//+Show+the+image.
}|code-block|syntax|javascript|239397|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

A piece of code is easier for people who have such problem. I share my code and you can use it directly. Please note that OpenCV store pixels as BGR.

<pre><code>cv::Mat vImage_; 

if(src_)
{
 cv::Vec3f vec_;

 for(int i = 0; i &lt; vHeight_; i++)
 for(int j = 0; j &lt; vWidth_; j++)
 {
 vec_ = cv::Vec3f((*src_)[0]/255.0, (*src_)[1]/255.0, (*src_)[2]/255.0);//Please note that OpenCV store pixels as BGR.

 vImage_.at&lt;cv::Vec3f&gt;(vHeight_-1-i, j) = vec_;

 ++src_;
 }
}

if(! vImage_.data ) // Check for invalid input
 printf("failed to read image by OpenCV.");
else
{
 cv::namedWindow( windowName_, CV_WINDOW_AUTOSIZE);
 cv::imshow( windowName_, vImage_); // Show the image.
}
</code></pre>

blocks|key|3126713|text|const+double+pi+=+boost::math::constants::pi<double>();

cv::Mat+distance2ellipse(cv::Mat+image,+cv::RotatedRect+ellipse){
++++float+distance+=+2.0f;
++++float+angle+=+ellipse.angle;
++++cv::Point+ellipse_center+=+ellipse.center;
++++float+major_axis+=+ellipse.size.width/2;
++++float+minor_axis+=+ellipse.size.height/2;
++++cv::Point+pixel;
++++float+a,b,c,d;

++++for(int+x+=+0;+x+<+image.cols;+x%2B%2B)
++++{
++++++++for(int+y+=+0;+y+<+image.rows;+y%2B%2B)+
++++++++{
++++++++auto+u+=++cos(angle*pi/180)*(x-ellipse_center.x)+%2B+sin(angle*pi/180)*(y-ellipse_center.y);
++++++++auto+v+=+-sin(angle*pi/180)*(x-ellipse_center.x)+%2B+cos(angle*pi/180)*(y-ellipse_center.y);

++++++++distance+=+(u/major_axis)*(u/major_axis)+%2B+(v/minor_axis)*(v/minor_axis);++

++++++++if(distance<=1)
++++++++{
++++++++++++image.at<cv::Vec3b>(y,x)[1]+=+255;
++++++++}
++++++}
++}
++return+image;++
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|3126714|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>const double pi = boost::math::constants::pi&lt;double&gt;();

cv::Mat distance2ellipse(cv::Mat image, cv::RotatedRect ellipse){
 float distance = 2.0f;
 float angle = ellipse.angle;
 cv::Point ellipse_center = ellipse.center;
 float major_axis = ellipse.size.width/2;
 float minor_axis = ellipse.size.height/2;
 cv::Point pixel;
 float a,b,c,d;

 for(int x = 0; x &lt; image.cols; x++)
 {
 for(int y = 0; y &lt; image.rows; y++) 
 {
 auto u = cos(angle*pi/180)*(x-ellipse_center.x) + sin(angle*pi/180)*(y-ellipse_center.y);
 auto v = -sin(angle*pi/180)*(x-ellipse_center.x) + cos(angle*pi/180)*(y-ellipse_center.y);

 distance = (u/major_axis)*(u/major_axis) + (v/minor_axis)*(v/minor_axis); 

 if(distance&lt;=1)
 {
 image.at&lt;cv::Vec3b&gt;(y,x)[1] = 255;
 }
 }
 }
 return image; 
}
</code></pre>

blocks|key|239399|text|uchar+*+value+=+img2.data;+//Pointer+to+the+first+pixel+data+,it's+return+array+in+all+values+
int+r+=+2;
for+(size_t+i+=+0;+i+<+img2.cols*+(img2.rows+*+img2.channels());+i%2B%2B)
{

++++++++if+(r+>+2)+r+=+0;

++++++++if+(r+==+0)+value[i]+=+0;
++++++++if+(r+==+1)value[i]+=++0;
++++++++if+(r+==+2)value[i]+=+255;

++++++++r%2B%2B;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|239400|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>uchar * value = img2.data; //Pointer to the first pixel data ,it's return array in all values 
int r = 2;
for (size_t i = 0; i &lt; img2.cols* (img2.rows * img2.channels()); i++)
{

 if (r &gt; 2) r = 0;

 if (r == 0) value[i] = 0;
 if (r == 1)value[i] = 0;
 if (r == 2)value[i] = 255;

 r++;
}
</code></pre>

I have searched internet and stackoverflow thoroughly, but I haven't found answer to my question:

How can I get/set (both) RGB value of certain (given by x,y coordinates) pixel in OpenCV? What's important-I'm writing in C++, the image is stored in cv::Mat variable. I know there is an IplImage() operator, but IplImage is not very comfortable in use-as far as I know it comes from C API.

Yes, I'm aware that there was already this <a href="https://stackoverflow.com/questions/4742251/pixel-access-in-opencv-2-2">Pixel access in OpenCV 2.2</a> thread, but it was only about black and white bitmaps.

EDIT:

Thank you very much for all your answers. I see there are many ways to get/set RGB value of pixel. I got one more idea from my close friend-thanks Benny! It's very simple and effective. I think it's a matter of taste which one you choose.

<pre><code>Mat image;
</code></pre>

(...)

<pre><code>Point3_&lt;uchar&gt;* p = image.ptr&lt;Point3_&lt;uchar&gt; &gt;(y,x);
</code></pre>

And then you can read/write RGB values with:

<pre><code>p-&gt;x //B
p-&gt;y //G
p-&gt;z //R
</code></pre>

Accessing certain pixel RGB value in openCV

我已经彻底搜索了互联网和stackoverflow，但我还没有找到我的问题的答案：如何在OpenCV中获取/设置(两者)特定(由x，y坐标给出)像素的RGB值？重要的是-我是用C++编写的，图像存储在cv::Mat变量中。我知道有一个IplImage()运算符，但是IplImage使用起来并不是很舒服--据我所知它来自...

问访问openCV中的某些像素RGB值
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