dd a note in findcontours doc

modules/imgproc/include/opencv2/imgproc.hpp

@@ -3744,6 +3744,7 @@ CV_EXPORTS_W int connectedComponentsWithStats(InputArray image, OutputArray labe
 The function retrieves contours from the binary image using the algorithm @cite Suzuki85 . The contours
 are a useful tool for shape analysis and object detection and recognition. See squares.cpp in the
 OpenCV sample directory.
+@note Since opencv 3.2 source image is not modified by this function.
 
 @param image Source, an 8-bit single-channel image. Non-zero pixels are treated as 1's. Zero
 pixels remain 0's, so the image is treated as binary . You can use cv::compare, cv::inRange, cv::threshold ,