Bandwidth Conservation Society /
Tutorial / Comparison Number 2 / CRLI
5-Bit GIF, Adaptive Palette / 7,554 Bytes
This image was opened and saved using Adobe Photoshop (v2.5.1). The
original PICT was converted to 5-Bit Indexed Color using an Adaptive Palette,
No Diffusion. The flattening (posterization) of the colors (in the shadow areas
and in the sky), is a modest cost when compared to the massive decrease in
5-Bit GIF, Adaptive Palette / CRLI / 4,434 Bytes
Consecutive Run Length Insertion is a compression overlay strategy to the
GIF format. With the understanding that GIF uses a Run Length Encoding (RLE) method
to provide optimum compression, the insertion of 1-pixel, mono-color bands at a
regular intervals utilizes the strengths of RLE. Note: For optimum compression
enhancement use Horizontal bands.
4-Bit GIF, Adaptive Palette / CRLI / 3,275 Bytes
Taking the CRLI strategy to the extreme, this is a 4-bit file. While
probably too radical for everyday applications this format may allow the clever
webmaster to use larger screen-acreage, tighter, more compact graphics.
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