colRange method
Creates a matrix header for the specified column span.
The method makes a new header for the specified column span of the matrix. Similarly to Mat::row and Mat::col , this is an O(1) operation.
https://docs.opencv.org/4.x/d3/d63/classcv_1_1Mat.html#aadc8f9210fe4dec50513746c246fa8d9
Implementation
Mat colRange(int start, int end) {
final p = calloc<cvg.Mat>();
cvRun(() => cffi.Mat_colRange(ref, start, end, p));
final dst = Mat._(p);
return dst;
}