How can i obtain a nice contour of a cropped and median filtered image?

When i use the contour function on my image obtained after cropping and median filtering the image is giving a very bad contour and that too in black and white but when i apply the contour function to this image (cropped and filter) seperately the output is nice. My requirement is to obtain this task with a single code. If anyone can tell me a method apart from this or suggest a suitable method it would be very helpful.