Bandwidth Conservation Society /
Tutorial / Comparison Number 2
JPEG Source File / 25,874 Bytes
For comparison, we've included the source file in JPEG format. The image
was orginally designed and rendered with KPT Bryce as a Macintosh PICT file. It
was then opened and saved using GIF Converter. The JPEG options were set to No Compression and
Millions of Colors.
8-Bit GIF, System Palette / 12,594 Bytes
Here, the image was opened and saved using Adobe Photoshop (v2.5.1). The
original PICT was converted to Index Color, with the System Palette and
Diffusion options selected.
Notice the heavy dithering in the sky and shadow areas. By forcing the image
into the available 256 Macintosh System colors, the heavy dithering encumbers
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
There is one more radical trick the brash webmaster can perform. Dubbed
Consecutive Run Length Data Insertion (CRLI, perhaps pronounced "curly"),
this one can pull another 3K off the already compact 7.5k image. There is a cost.
Take a look.
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