blocks|key|525775|text|请参阅Accessing+a+matrix+element+in+the+"Mat"+object+(not+the+CvMat+object)+in+OpenCV+C%2B%2B的第一个答案|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|525776|然后循环遍历cout+<<+M.at<double>(0,0);中的所有元素，而不仅仅是0,0|style|CODE|525777|或者更好的是使用C%2B%2B接口：|525778|cv::Mat+M;
cout+<<+"M+=+"+<<+endl+<<+"+"++<<+M+<<+endl+<<+endl;|code-block|syntax|javascript|525779|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/1844736/accesing-a-matrix-element-in-the-mat-object-not-the-cvmat-object-in-opencv-c^0|3|2B|0|0|6|Q|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|6|7|10|8|@$A|11|B|12|F|G]]|9|@]|C|$]]|$1|H|3|I|5|6|7|13|8|@]|9|@]|C|$]]|$1|J|3|K|5|L|7|14|8|@]|9|@]|C|$M|N]]|$1|O|3|-4|5|6|7|15|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]]]

See the first answer to <a href="https://stackoverflow.com/questions/1844736/accesing-a-matrix-element-in-the-mat-object-not-the-cvmat-object-in-opencv-c">Accessing a matrix element in the &quot;Mat&quot; object (not the CvMat object) in OpenCV C++</a> 
Then just loop over all the elements in <code>cout &lt;&lt; M.at&lt;double&gt;(0,0);</code> rather than just 0,0

Or better still with the C++ interface:

<pre><code>cv::Mat M;
cout &lt;&lt; "M = " &lt;&lt; endl &lt;&lt; " " &lt;&lt; M &lt;&lt; endl &lt;&lt; endl;
</code></pre>

blocks|key|525790|text|#include+<opencv2/imgproc/imgproc.hpp>
#include+<opencv2/highgui/highgui.hpp>

#include+<iostream>
#include+<iomanip>

using+namespace+cv;
using+namespace+std;

int+main(int+argc,+char**+argv)
{
++++double+data[4]+=+{-0.0000000077898273846583732,+-0.03749374753019832,+-0.0374787251930463,+-0.000000000077893623846343843};
++++Mat+src+=+Mat(1,+4,+CV_64F,+&data);
++++for(int+i=0;+i<4;+i%2B%2B)
++++++++cout+<<+setprecision(3)+<<+src.at<double>(0,i)+<<+endl;

++++return+0;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|525791|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>#include &lt;opencv2/imgproc/imgproc.hpp&gt;
#include &lt;opencv2/highgui/highgui.hpp&gt;

#include &lt;iostream&gt;
#include &lt;iomanip&gt;

using namespace cv;
using namespace std;

int main(int argc, char** argv)
{
 double data[4] = {-0.0000000077898273846583732, -0.03749374753019832, -0.0374787251930463, -0.000000000077893623846343843};
 Mat src = Mat(1, 4, CV_64F, &amp;data);
 for(int i=0; i&lt;4; i++)
 cout &lt;&lt; setprecision(3) &lt;&lt; src.at&lt;double&gt;(0,i) &lt;&lt; endl;

 return 0;
}
</code></pre>

blocks|key|742344|text|我认为使用matrix.at<type>(x,y)不是通过Mat对象进行迭代的最佳方式！如果我没记错的话，每次调用矩阵时，matrix.at<type>(x,y)都会从矩阵的开头开始迭代(不过我可能错了)。我建议使用cv::MatIterator_|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|742345|cv::Mat+someMat(1,+4,+CV_64F,+&someData);;
cv::MatIterator_<double>+_it+=+someMat.begin<double>();
for(;_it!=someMat.end<double>();+_it%2B%2B){
++++std::cout+<<+*_it+<<+std::endl;
}|code-block|syntax|javascript|742346|entityMap^0|5|K|1P|K|30|G|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|U|8|@]|D|@]|E|$]]]|L|$]]

I think using the <code>matrix.at&lt;type&gt;(x,y)</code> is not the best way to iterate trough a Mat object!
If I recall correctly <code>matrix.at&lt;type&gt;(x,y)</code> will iterate from the beginning of the matrix each time you call it(I might be wrong though).
I would suggest using <code>cv::MatIterator_</code>

<pre><code>cv::Mat someMat(1, 4, CV_64F, &amp;someData);;
cv::MatIterator_&lt;double&gt; _it = someMat.begin&lt;double&gt;();
for(;_it!=someMat.end&lt;double&gt;(); _it++){
 std::cout &lt;&lt; *_it &lt;&lt; std::endl;
}
</code></pre>

blocks|key|525993|text|如果您使用的是opencv3，则可以像python+numpy+style一样打印Mat|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|525994|Mat+xTrainData+=+(Mat_<float>(5,2)+<<+1,+1,+1,+1,+2,+2,+2,+2,+2,+2);

cout+<<+"xTrainData+(python)++=+"+<<+endl+<<+format(xTrainData,+Formatter::FMT_PYTHON)+<<+endl+<<+endl;|code-block|syntax|javascript|525995|输出如下所示，你可以看到它更具可读性，更多信息请参见here。|525996|​|525997|📷|atomic|525998|525999|但在大多数情况下，不需要输出Mat中的所有数据，可以按行范围输出，如0~2行：|526000|#include+<opencv2/imgproc/imgproc.hpp>
#include+<opencv2/highgui/highgui.hpp>

#include+<iostream>
#include+<iomanip>

using+namespace+cv;
using+namespace+std;

int+main(int+argc,+char**+argv)
{
++++//row:+6,+column:+3，unsigned+one+channel
++++Mat+image1(6,+3,+CV_8UC1,+5);

++++//+output+row:+0+~+2
++++cout+<<+"image1+row:+0~2+=+"<<+endl+<<+"+"++<<+image1.rowRange(0,+2)+<<+endl+<<+endl;

++++//row:+8,+column:+2，unsigned+three+channel
++++Mat+image2(8,+2,+CV_8UC3,+Scalar(1,+2,+3));

++++//+output+row:+0+~+2
++++cout+<<+"image2+row:+0~2+=+"<<+endl+<<+"+"++<<+image2.rowRange(0,+2)+<<+endl+<<+endl;

++++return+0;
}|526001|输出如下：|526002|526003|526004|526005|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.opencv.org/3.1.0/d6/d6d/tutorial_mat_the_basic_image_container.html|1|IMAGE|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/0bf80050a5db7dbec35d174f3e0c4855.png|imageAlt|2|https://ask.qcloudimg.com/http-save/yehe-900000/09b0628b2e09baf5acbc015d7beefb42.png^0|J|I|0|0|Q|4|0|0|0|0|1|1|0|0|0|0|0|0|0|1|2|0|0^^$0|@$1|2|3|4|5|6|7|1H|8|@$9|1I|A|1J|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|1K|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1L|8|@]|D|@$9|1M|A|1N|1|1O]]|E|$]]|$1|M|3|N|5|6|7|1P|8|@]|D|@]|E|$]]|$1|O|3|P|5|Q|7|1Q|8|@]|D|@$9|1R|A|1S|1|1T]]|E|$]]|$1|R|3|N|5|6|7|1U|8|@]|D|@]|E|$]]|$1|S|3|T|5|6|7|1V|8|@]|D|@]|E|$]]|$1|U|3|V|5|H|7|1W|8|@]|D|@]|E|$I|J]]|$1|W|3|X|5|6|7|1X|8|@]|D|@]|E|$]]|$1|Y|3|N|5|6|7|1Y|8|@]|D|@]|E|$]]|$1|Z|3|P|5|Q|7|1Z|8|@]|D|@$9|20|A|21|1|22]]|E|$]]|$1|10|3|N|5|6|7|23|8|@]|D|@]|E|$]]|$1|11|3|-4|5|6|7|24|8|@]|D|@]|E|$]]]|12|$13|$5|14|15|16|E|$17|18]]|19|$5|1A|15|1B|E|$1C|1D|1E|-4]]|1F|$5|1A|15|1B|E|$1C|1G|1E|-4]]]]

If you are using opencv3, you can print Mat like <code>python numpy style</code>:

<pre><code>Mat xTrainData = (Mat_&lt;float&gt;(5,2) &lt;&lt; 1, 1, 1, 1, 2, 2, 2, 2, 2, 2);

cout &lt;&lt; "xTrainData (python) = " &lt;&lt; endl &lt;&lt; format(xTrainData, Formatter::FMT_PYTHON) &lt;&lt; endl &lt;&lt; endl;
</code></pre>

Output as below, you can see it'e more readable, see <a href="https://docs.opencv.org/3.1.0/d6/d6d/tutorial_mat_the_basic_image_container.html" rel="noreferrer">here</a> for more information.

<a href="https://i.stack.imgur.com/wSBkr.png" rel="noreferrer"><img src="https://i.stack.imgur.com/wSBkr.png" alt="enter image description here"></a>

But in most case, there is no need to output all the data in Mat, you can output by row range like 0 ~ 2 row:

<pre><code>#include &lt;opencv2/imgproc/imgproc.hpp&gt;
#include &lt;opencv2/highgui/highgui.hpp&gt;

#include &lt;iostream&gt;
#include &lt;iomanip&gt;

using namespace cv;
using namespace std;

int main(int argc, char** argv)
{
 //row: 6, column: 3，unsigned one channel
 Mat image1(6, 3, CV_8UC1, 5);

 // output row: 0 ~ 2
 cout &lt;&lt; "image1 row: 0~2 = "&lt;&lt; endl &lt;&lt; " " &lt;&lt; image1.rowRange(0, 2) &lt;&lt; endl &lt;&lt; endl;

 //row: 8, column: 2，unsigned three channel
 Mat image2(8, 2, CV_8UC3, Scalar(1, 2, 3));

 // output row: 0 ~ 2
 cout &lt;&lt; "image2 row: 0~2 = "&lt;&lt; endl &lt;&lt; " " &lt;&lt; image2.rowRange(0, 2) &lt;&lt; endl &lt;&lt; endl;

 return 0;
}
</code></pre>

Output as below:

<a href="https://i.stack.imgur.com/yt4sG.png" rel="noreferrer"><img src="https://i.stack.imgur.com/yt4sG.png" alt="enter image description here"></a>

blocks|key|526056|text|除了上面的优秀答案之外，您还可以通过FileStorage打印Mat值，当然，如果您的情况考虑使用文件|type|unstyled|depth|inlineStyleRanges|entityRanges|data|526057|//+create+our+writer+
FileStorage+fs("test.yml",+FileStorage::WRITE);
fs+<<+"Result"+<<+Mat::eye(5,5,+CV_64F);
//+release+the+file+
fs.release();

//+read+file
FileStorage+fs2("test.yml",+FileStorage::READ);

Mat+r2;
fs2["Result"]+>>+r2;
std::cout+<<+r2+<<+std::endl;

fs2.release();|code-block|syntax|javascript|526058|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|$]]

Additionally to the above excellent answers, you can print out Mat values by FileStorage, of course if your case considers utilizing a file
<pre><code>// create our writer 
FileStorage fs(&quot;test.yml&quot;, FileStorage::WRITE);
fs &lt;&lt; &quot;Result&quot; &lt;&lt; Mat::eye(5,5, CV_64F);
// release the file 
fs.release();

// read file
FileStorage fs2(&quot;test.yml&quot;, FileStorage::READ);

Mat r2;
fs2[&quot;Result&quot;] &gt;&gt; r2;
std::cout &lt;&lt; r2 &lt;&lt; std::endl;

fs2.release();
</code></pre>

I want to dump the values of a matrix in OpenCV to the console using cout. I quickly learned that I do not understand OpenvCV's type system nor C++ templates well enough to accomplish this simple task.

Would a reader please post (or point me to) a little function or code snippet that prints a Mat?

Regards,
Aaron

PS: Code that uses the newer C++ Mat interface as opposed to the older CvMat interface is preferential.

Print out the values of a (Mat) matrix in OpenCV C++

我想使用cout将OpenCV中的矩阵的值转储到控制台。我很快意识到，我对OpenvCV的类型系统和C++模板的理解还不够好，无法完成这个简单的任务。能不能请读者发个帖子(或者给我指给我)一个打印Mat的小函数或代码片段？向你致敬，亚伦PS:使用较新的C++ Mat接口而不是较旧的CvMat接口的代码优先。

问在OpenCV C++中打印出(Mat)矩阵的值
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