Non-Photorealistic Rendering

edgePreservingFilter

Filtering is the fundamental operation in image and video processing. Edge-preserving smoothing filters are used in many different applications [EM11].

C++: void edgePreservingFilter(InputArray src, OutputArray dst, int flags=1, float sigma_s=60, float sigma_r=0.4f)

Parameters:

• src – Input 8-bit 3-channel image.
• dst – Output 8-bit 3-channel image.
• flags –

  Edge preserving filters:

  • RECURS_FILTER = 1
  • NORMCONV_FILTER = 2
• sigma_s – Range between 0 to 200.
• sigma_r – Range between 0 to 1.

detailEnhance

This filter enhances the details of a particular image.

C++: void detailEnhance(InputArray src, OutputArray dst, float sigma_s=10, float sigma_r=0.15f)

Parameters:

• src – Input 8-bit 3-channel image.
• dst – Output image with the same size and type as src.
• sigma_s – Range between 0 to 200.
• sigma_r – Range between 0 to 1.

pencilSketch

Pencil-like non-photorealistic line drawing

C++: void pencilSketch(InputArray src, OutputArray dst1, OutputArray dst2, float sigma_s=60, float sigma_r=0.07f, float shade_factor=0.02f)

Parameters:

• src – Input 8-bit 3-channel image.
• dst1 – Output 8-bit 1-channel image.
• dst2 – Output image with the same size and type as src.
• sigma_s – Range between 0 to 200.
• sigma_r – Range between 0 to 1.
• shade_factor – Range between 0 to 0.1.

stylization

Stylization aims to produce digital imagery with a wide variety of effects not focused on photorealism. Edge-aware filters are ideal for stylization, as they can abstract regions of low contrast while preserving, or enhancing, high-contrast features.

C++: void stylization(InputArray src, OutputArray dst, float sigma_s=60, float sigma_r=0.45f)

Parameters:

• src – Input 8-bit 3-channel image.
• dst – Output image with the same size and type as src.
• sigma_s – Range between 0 to 200.
• sigma_r – Range between 0 to 1.

[EM11]

Eduardo S. L. Gastal, Manuel M. Oliveira, “Domain transform for edge-aware image and video processing”, ACM Trans. Graph. 30(4): 69, 2011.