add note about "maxCorners <= 0" case in goodFeaturesToTrack

modules/imgproc/include/opencv2/imgproc.hpp

@@ -1828,7 +1828,8 @@ with qualityLevel=B .
 @param image Input 8-bit or floating-point 32-bit, single-channel image.
 @param corners Output vector of detected corners.
 @param maxCorners Maximum number of corners to return. If there are more corners than are found,
-the strongest of them is returned.
+the strongest of them is returned. `maxCorners <= 0` implies that no limit on the maximum is set
+and all detected corners are returned.
 @param qualityLevel Parameter characterizing the minimal accepted quality of image corners. The
 parameter value is multiplied by the best corner quality measure, which is the minimal eigenvalue
 (see cornerMinEigenVal ) or the Harris function response (see cornerHarris ). The corners with the