Size of Matrix OpenCV

Question

I know this might be very rudimentary  but I am new to OpenCV  Could you please tell me how to obtain the size of a matrix in OpenCV   I googled and I am still searching  but if any of you know the answer  please help me   Size as in number of rows and columns   And is there a way to directly obtain the maximum value of a 2D matrix

User · Answer

Note that apart from rows and columns there is a number of channels and type. When it is clear what type is, the channels can act as an extra dimension as in CV_8UC3 so you would address a matrix as

uchar a = M.at<Vec3b>(y, x)[i];

So the size in terms of elements of elementary type is M.rows * M.cols * M.cn

To find the max element one can use

Mat src;
double minVal, maxVal;
minMaxLoc(src, &minVal, &maxVal);

User · Answer

cv Mat mat  int rows   mat rows  int cols   mat cols   cv  Size s   mat size    rows   s height  cols   s width    Also note that stride    cols  this means that actual size of the row can be greater than element size x cols  This is different from the issue of continuous Mat and is related to data alignment

User · Answer

For 2D matrix   mat rows     Number of rows in a 2D array   mat cols     Number of columns in a 2D array   Or  C    Size Mat  size   const  The method returns a matrix size  Size cols  rows    When the matrix is more than 2-dimensional  the returned size is  -1  -1    For multidimensional matrix  you need to use   int thisSizes 3     2  3  4   cv  Mat mat3D 3  thisSizes  CV 32FC1      mat3D size tells the size of the matrix     mat3D size 0    2     mat3D size 1    3     mat3D size 2    4    Note  here 2 for z axis  3 for y axis  4 for x axis  By x  y  z  it means the order of the dimensions  x index changes the fastest

User · Answer

A complete C   code example  may be helpful for the beginners   include  lt iostream gt   include  lt string gt   include  opencv highgui h   using namespace std  using namespace cv   int main         cv Mat M 102 201 CV 8UC1       int rows   M rows      int cols   M cols       cout lt  lt rows lt  lt     lt  lt cols lt  lt endl       cv  Size sz   M size        rows   sz height      cols   sz width       cout lt  lt rows lt  lt     lt  lt cols lt  lt endl      cout lt  lt sz lt  lt endl      return 0

User · Answer

If you are using the Python wrappers  then  assuming your matrix name is mat     mat shape gives you an array of the type-  height  width  channels  mat size gives you the size of the array   Sample Code   import cv2 mat   cv2 imread  sample png   height  width  channel   mat shape  3  size   mat size

[opencv] Size of Matrix OpenCV

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