OpenCV create Mat from byte array

Question

In my C++ dll I am creating Mat from byte array:

BYTE * ptrImageData;  //Image data is in this array passed to this function

Mat newImg = Mat(nImageHeight,          


        

Answer 1

Here is link to docs: http://docs.opencv.org/modules/core/doc/basic_structures.html#mat-mat

In general you should take care about two things:

1. When you pass external data into matrix constructor, the external data is not automatically deallocated, so you should take care of it. If you want OpenCV matrix to care about memory, then you should copy matrix (you can do it in many ways, e.g. using Mat::clone or Mat::copyTo methods.
2. External data may not be continuous, i.e. size of row may be bigger than width multiplied by number of channels multiplied by size of data element. So you may want specify "step" as last argument of constructor. If you allocate external data manually and 100% sure that it is continuous, then you may not pass step and rely on automatic step calculation.

I am not familiar with C#, but it seems to me that you release data right after ProcessImage call. So if ProcessImage is asynchronous or somehow caches your matrix (i.e. lifetime of matrix is longer that ProcessImage call), then you should care about memory management.