Can I determine the number of channels in cv::Mat Opencv

Question

This maybe rudimentary, but is it possible to know how many channels a cv::Mat has? For eg, we load an RGB image, I know there are 3 channels. I do the following operations, just to get the laplacian of the image, which is straight from the Opencv Documentation.

int main(int argc, char **argv)
{
     Mat src = imread(argv[1],1),src_gray,dst_gray,abs_dst_gray;

     cvtColor(src,src_gray,COLOR_BGR2GRAY);
     GaussianBlur( src, src, Size(3,3), 0, 0, BORDER_DEFAULT );
     Laplacian(src_gray,dst_gray,ddepth,kernel_size,scale,delta,BORDER_DEFAULT);
     convertScaleAbs(dst_gray,abs_dst_gray);
}

After converting to Grayscale, we should have only one channel. But how can I determine the number of channels of abs_dst_gray in program? Is there any function to do this? Or is it possible through any other method, which should be written by the programmer? Please help me here.

Thanks in advance.

Have a look at the anser i gave in another thread. I explained how to get the cannels and type of a matrix and how you can access single elements afterwards: http://stackoverflow.com/questions/7399344/save-cv-16sc2-mat-to-a-file-opencv/22102303#22102303 — Sebastian Schmitz, Mar 27 '14 at 11:08

score 63 · Accepted Answer · answered Jun 28 '13 at 11:55

63

Call Mat.channels() :

cv::Mat img(1,1,CV_8U,cvScalar(0));
std::cout<<img.channels();

Output:

which is the number of channels.

Also, try:

std::cout<<img.type();

Output:

which belongs to CV_8U (look here at line 542). Study file types_c.h for each define.

answered Jun 28 '13 at 11:55

LovaBill

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This gives the data type @William. How do I get the no.of channels? – Lakshmi Narayanan Jun 28 '13 at 11:57
1

Of course. Everybody here are willing to help, @LakshmiNarayanan. Just post, and if I have some free time, I'll give it a try. – LovaBill Jun 28 '13 at 12:13
2

@LakshmiNarayanan Post the other doubt in a new question please. – hetepeperfan Jun 28 '13 at 12:19
@hetepeperfan I have asked it here http://stackoverflow.com/questions/17364987/knowing-the-value-of-an-mat-element-opencv Please bare with me if its pretty rudimentary. – Lakshmi Narayanan Jun 28 '13 at 12:42
3

William's link seems dead. Here's a substitute: http://ninghang.blogspot.co.uk/2012/11/list-of-mat-type-in-opencv.html – Sipty Oct 22 '15 at 14:40

score 14 · Answer 2 · answered Jun 28 '13 at 11:57

14

you might use:

Mat::channels()

http://docs.opencv.org/modules/core/doc/basic_structures.html#mat-channels

answered Jun 28 '13 at 11:57

hetepeperfan

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Can I determine the number of channels in cv::Mat Opencv

2 Answers2

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