Non-Photorealistic Computer Graphics

Content

• Pixel Manipulation of Images

  • Halftoning Methods

    • • Ordered Dithering (Takeaway Concept: Dither Matrix pattern and/or size can be modified to create image artifacts/patterns)

      • Error Diffusion (Takeaway Concept: Rendered output and error computation can be modified in the Floyd-Steinberg algorithm to create image artifacts/patterns)

• • • Screening - note that each of the following methods are image-independent dithering methods.

    • Basic Method

      • Tuning Image and Screen Intensities - Histogram Equalization, Block-by-Block Histogram Equalization of Dither Screens, Adaptive Histogram Equalization of Dither Screens

      • Procedural Screening - (Takeaway Concept: separate concerns into 2 separate problems, 1 dealing with the intensity computation and 1 dealing with mapping positions)

        • dither kernel - compute an intensity level for each pair of input values s and t (where s, t are within [0, 1])

        • mapping function - transforms input pixel positions (x, y) into pairs of parameters (s, t)

    • Embedding Shapes in Dither Screens - average intensity of blocks to find corresponding symbol.

    • Screening with Texts

    • Embedding Morphed Contours

• • Stippling

    • • Automatic Methods - treat density as height map. If random value at location is > height, then render dot.

References