Made it so contours are drawn on copy of original image, rather than original
Made it so contours are drawn on copy of original image, rather than original

stiphyMT/plantcv,stiphyMT/plantcv,AntonSax/plantcv,danforthcenter/plantcv,danforthcenter/plantcv,stiphyMT/plantcv,jshoyer/plantcv,AntonSax/plantcv,danforthcenter/plantcv,jshoyer/plantcv