Dither

Dithering is the intentional use of noise to reduce the error of compression.

Example below:

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  Figure 1. Original photo; note the smoothness in the detail.

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  Figure 2. Original image using the web-safe color palette with no dithering applied. Note the large flat areas and loss of detail.

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  Figure 3. Original image using the web-safe color palette with Floyd–Steinberg dithering. Note that even though the same palette is used, the application of dithering gives a better representation of the original.

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  Figure 4. Here, the original has been reduced to a 256-color optimized palette with Floyd–Steinberg dithering applied. The use of an optimized palette, rather than a fixed palette, allows the result to better represent the colors in the original image.

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  Figure 5. Depth is reduced to a 16-color optimized palette in this image, with no dithering. Colors appear muted, and color banding is pronounced.

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  Figure 6. This image also uses the 16-color optimized palette, but the use of dithering helps to reduce banding.

Dither Media

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  Reducing amplitude resolution plot

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  An illustration of dithering. Red and blue are the only colors used but, as the red and blue squares are made smaller, the patch appears magenta.

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  256 color dithering with IrfanView

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  Color dithering on a towel

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  A smooth gradient using ordered dithering from black to white, using only three colors (black, gray and white)

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  Michelangelo's David - 63 grijswaarden

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  Michelangelo's David - drempel

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  Michelangelo's David - ruis

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  Michelangelo's David - halftoon