Mastering OpenCV with Practical Computer Vision Projects

Generating a black-and-white sketch

To obtain a sketch (black-and-white drawing) of the camera frame, we will use an edge-detection filter; whereas to obtain a color painting, we will use an edge-preserving filter (bilateral filter) to further smooth the flat regions while keeping the edges intact. By overlaying the sketch drawing on top of the color painting, we obtain a cartoon effect as shown earlier in the screenshot of the final app.

There are many different edge detection filters, such as Sobel, Scharr, Laplacian filters, or Canny-edge detector. We will use a Laplacian edge filter since it produces edges that look most similar to hand sketches compared to Sobel or Scharr, and that are quite consistent compared to a Canny-edge detector, ...