%DRAWKEYPOINTS  Draws keypoints
%
%    im = cv.drawKeypoints(im, keypoints)
%    im = cv.drawKeypoints(im, keypoints, 'OptionName', optionValue, ...)
%
% ## Input
% * __im__ Image on which keypoints are to be drawn.
% * __keypoints__ Keypoints from the source image. A 1-by-N structure array.
%       It has the following fields:
%       * __pt__ coordinates of the keypoint [x,y]
%       * __size__ diameter of the meaningful keypoint neighborhood
%       * __angle__ computed orientation of the keypoint (-1 if not applicable).
%             Its possible values are in a range [0,360) degrees. It is measured
%             relative to image coordinate system (y-axis is directed downward),
%             ie in clockwise.
%       * __response__ the response by which the most strong keypoints have been
%             selected. Can be used for further sorting or subsampling.
%       * __octave__ octave (pyramid layer) from which the keypoint has been
%             extracted.
%       * **class_id** object id that can be used to clustered keypoints by an
%             object they belong to.
%
% ## Output
% * __im__ Output image. Its content depends on the option values defining
%         what is drawn in the output image. See possible options below.
%         By default, the source image, and single keypoints will be drawn.
%         For each keypoint, only the center point will be drawn (without
%         a circle around the keypoint with the keypoint size and orientation).
%
% ## Options
% * __Color__ Color of keypoints. If all -1, random colors are picked up.
%         default [-1,-1,-1,-1]
% * __NotDrawSinglePoints__ Single keypoints will not be drawn. default
%         false.
% * __DrawRichKeypoints__ For each keypoint, the circle around keypoint
%         with keypoint size and orientation will be drawn. default false.
%
% See also cv.drawMatches
%