Documented the Python version of findContours (issue #1697)

modules/imgproc/doc/structural_analysis_and_shape_descriptors.rst

@@ -124,6 +124,8 @@ Finds contours in a binary image.
 
 .. ocv:function:: void findContours( InputOutputArray image, OutputArrayOfArrays contours, int mode, int method, Point offset=Point())
 
+.. ocv:pyfunction:: cv2.findContours(image, mode, method[, contours[, hierarchy[, offset]]]) -> contours, hierarchy
+
 .. ocv:cfunction:: int cvFindContours( CvArr* image, CvMemStorage* storage, CvSeq** firstContour, int headerSize=sizeof(CvContour), int mode=CV_RETR_LIST, int method=CV_CHAIN_APPROX_SIMPLE, CvPoint offset=cvPoint(0, 0) )
 
 .. ocv:pyoldfunction:: cv.FindContours(image, storage, mode=CV_RETR_LIST, method=CV_CHAIN_APPROX_SIMPLE, offset=(0, 0)) -> cvseq
@@ -134,7 +136,7 @@ Finds contours in a binary image.
 
     :param hierarchy: Optional output vector containing information about the image topology. It has as many elements as the number of contours. For each contour  ``contours[i]`` , the elements  ``hierarchy[i][0]`` ,  ``hiearchy[i][1]`` ,  ``hiearchy[i][2]`` , and  ``hiearchy[i][3]``  are set to 0-based indices in  ``contours``  of the next and previous contours at the same hierarchical level: the first child contour and the parent contour, respectively. If for a contour  ``i``  there are no next, previous, parent, or nested contours, the corresponding elements of  ``hierarchy[i]``  will be negative.
 
-    :param mode: Contour retrieval mode.
+    :param mode: Contour retrieval mode (if you use Python see also a note below).
 
             * **CV_RETR_EXTERNAL** retrieves only the extreme outer contours. It sets  ``hierarchy[i][2]=hierarchy[i][3]=-1``  for all the contours.
 
@@ -144,7 +146,7 @@ Finds contours in a binary image.
 
             * **CV_RETR_TREE** retrieves all of the contours and reconstructs a full hierarchy of nested contours. This full hierarchy is built and shown in the OpenCV  ``contours.c``  demo.
 
-    :param method: Contour approximation method.
+    :param method: Contour approximation method (if you use Python see also a note below).
 
             * **CV_CHAIN_APPROX_NONE** stores absolutely all the contour points. That is, any 2 subsequent points ``(x1,y1)`` and ``(x2,y2)`` of the contour will be either horizontal, vertical or diagonal neighbors, that is, ``max(abs(x1-x2),abs(y2-y1))==1``.
 
@@ -159,6 +161,7 @@ The function retrieves contours from the binary image using the algorithm
 
 .. note:: Source ``image`` is modified by this function.
 
+.. note:: If you use the new Python interface then the ``CV_`` prefix has to be omitted in contour retrieval mode and contour approximation method parameters (for example, use ``cv2.RETR_LIST`` and ``cv2.CHAIN_APPROX_NONE`` parameters). If you use the old Python interface then these parameters have the ``CV_`` prefix (for example, use ``cv.CV_RETR_LIST`` and ``cv.CV_CHAIN_APPROX_NONE``).
 
 drawContours
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