Optimizing Web Graphics: GIF Plug-in Comparison | WebReference

Optimizing Web Graphics: GIF Plug-in Comparison

Figure 1b - GIF Plug-in Comparison (64/128-Color GIF)
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PS 64 colors Non-dithered 128 colors Dith. 134 Netscape
64 Colors = 8.4K128 Colors = 10.7KN/A Dithered 134* Netscape 13.4K
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PG 64 colors Non-dithered 128 colors 128 colors Optimized Dithered 128 Netscape
64 Colors = 10.1K128 Colors = 13.0K128 Colors Opt. = 12.2KDith. 128 Netscape** 13.1K
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DB 3 64 Colors Non-dithered 128 colors Dithered 134 Netscape
64 Colors = 10.3KNon-dith. = 13.5KN/ADith. 134* Netscape 13.0K
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IR Perceptive 64 Colors IR Perceptive128 Colors N/A 64 Colors  Dithered 63% Web
64 Colors Perceptive = 9.3K128 Colors Perceptive = 11.8KN/A64 Colors, dithered 63% Web = 9.4K
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FW 64 Colors FW 128 Colors N/A 64 Colors Dithered 64%
64 Colors = 9.7K128 Colors = 12.2KN/A64 Colors, dithered 63% Web = 10.5K
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ImageVice 64 Colors (zero Convergence) 128 Colors (zero convergence) 128 Colors (defaults) 64 Colors (defaults)
64 Colors (zero convergence) = 10.0K128 Colors (zero convergence) = 12.9K128 Colors Defaults = 11.5K64 Colors (Defaults) = 8.9K
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HVS 2 64 Colors (more shading) 128 Colors (more shading) N/A 64 Colors Dithered 64% Netscape
64 Colors (more shading) = 10.6K128 Colors (more shading) = 13.5KN/ADithered 64 Netscape** = 11.3K

GIF images were compressed in Photoshop 3.05 (with the GIF89a plug-in), PhotoGIF 2.0, Debabelizer 3, Imageready 1.0b2, Fireworks 1.0, ImageVice 1.0, and HVS ColorGIF 2.0. The default adaptive palette was used on all but the Netscape palette images and Imageready, which defaults to a perceptive palette (similar to HVS). (HVS ColorGIF version 2.0 was used at the more shading setting to minimize banding. ImageVice 1.0 was used at zero convergence (to minimize banding and horizontal lines) and at the default settings. Imageready and Fireworks were used at their default settings. Dith. = Dithered, Opt. = Optimize Palette. All images are Copyright 2001 Jupitermedia Corp. and may not be reused without the author's permission.

*In Photoshop there is no straightforward way to index an RGB image to a specific bit depth within a user-specified palette. The 134 colors in these images are the result of reducing to the 216-color non-dithering Netscape palette. In Debabelizer it's also difficult to reduce to the Netscape palette at a specific bit depth, but you can use the base palette selection method to do this. Debabelizer, Fireworks, and Imageready also work with all the plug-ins mentioned in this article, including HVS products. PhotoGIF, HVS ColorGIF, Fireworks, Imageready can all reduce to specific bit depths within fixed palettes.

**Note that when reducing directly from an RGB image to a subset of a fixed palette (in this case the Netscape 216-color palette) PhotoGIF stores the full palette. The two examples above use a trick to reduce the palette size to the exact number of colors used by opening the GIF, changing the mode to RGB, and indexing again to the exact number of colors. If you look at the color table before and after you'll see that it shrinks. This trick saves about .5K.

Comparison

GIFs

The programs are listed in order of color reduction quality, worst to first. Photoshop does not reduce full-color images as well as PhotoGIF, Debabelizer, Imageready, Fireworks, ImageVice, or HVS PhotoGIF. Note the blockiness and banding in the 64 and 128-color non-dithered GIFs. PhotoGIF reduces color better than Photoshop at the expense of some file size. Debabelizer reduces colors better than PhotoGIF at the expense of a slight increase in file size. Note that the color bands are less pronounced in the 128-color GIF. Imageready reduces colors better with the default "perceptive" palette vs. the adaptive palette, and produces smaller files with the perceptive palette. Imageready also produced slightly smaller files than Fireworks at the same bit depth, with the perceptive palette setting. Fireworks produced slightly smoother bands than Imageready, but the difference is subtle.

ImageVice 1.0 reduces colors better than Debabelizer 3, and is a marked improvement over BoxTop's other product PhotoGIF. HVS ColorGIF produces the smoothest banding, by a small margin over ImageVice. The 128 color images are nearly in indistinguishable.

Fireworks, ImageVice and HVS ColorGIF are in a class by themselves. All reduce color more intelligently with less discernible banding than all other tested programs. Fireworks, Imagevice, and ImageReady make short work out of the 128 color balloons, with smooth transitions between color bands. At the 64 color setting the quantization algorithms of these three programs starts to show in blocky bands, and HVS ColorGIF really shines. The quality of the 64-color GIF created by HVS ColorGIF is amazing. With extreme reductions like this, setting the "smoothing" setting (which controls how wide or noticeable the banding is) to the highest setting gives the best results. The file sizes are similar to PhotoGIF's at these settings, but can be decreased by setting the smoothing to a lower setting at the expense of increased banding.

Both PhotoGIF and HVS ColorGIF have an "Optimize Palette Usage" checkbox that removes little-used colors from the image, and reduces file size even further (though HVS ColorGIF 2.0 has this checkbox disabled on all but the Netscape palette). The documentation says to be careful with this option, as some images may degrade. Out of all these images I would use the HVS ColorGIF 128 Color Optimized image, at 13.5K.

Dithering - Photoshop offers only diffusion dithering while the other products offer adjustable amounts of dithering. Debabelizer has awesome control over color palettes, but there's no one-step way to reduce to a specific palette at a lower bit depth with or without dithering.

Comments are welcome


Created: June 10, 1996
Revised: Jun. 13, 1998

URL: http://webreference.com/dev/graphics/compare.html