c++ - OpenCV - Contour Lines on Gradient Every Interval -

c++ - OpenCV - Contour Lines on Gradient Every Interval -

i'm trying contour lines of next image: http://i.stack.imgur.com/j5zbm.png

what i'm trying lines every x amount of interval, either close if exclusively within image, or left open ended if nail black background.

i've tried 2 techniques using opencv , both don't quite give need.

the first utilize binary threshold every x interval , using find contours on temporary images. result close want, wraps around border of image. http://imgur.com/8fqhozs

the sec utilize inrange @ x interval values , find contours. eliminated wrapping problem, created issue thicker sections of 1 color create enclosed poly. http://imgur.com/wq2samb

has had experience trying similar? i'm collecting points , creating geo-spacial polys , lines, other alternative effort post processing, concerned speed of , rather in opencv if possible.

c++ opencv gradient contour