A Guide to Web image Compression Software: WebVise
Software type: GIF/JPEG optimisers
WebVise is a very sophisticated suite of programs that allows you to do a range of things to GIFs and JPEGs. It comes as a plugin to Photoshop and other packages like PaintShopPro, and also as a stand-alone version. The two versions come as separate demo programs. Both versions behave in exactly the same way.
It has a non-standard interface that is very elegant but a bit hard to get used to if you're used to the standard Windows or Mac message boxes. But it is a great deal easier to look at than the Alien Skin and Kai's Power Tools interfaces, which I find ugly and hard to use. I must concede I don't warm to it, but that's very much a matter of taste. One aspect I think is bad is that the interface box cannot be resized or moved: it sits in the middle of the screen whether you like it or not. It's sized to work best on a 640x480 screen. How many graphics designers use that these days?
The Photoshop plugin demo program (and the registered version, which the demo becomes when you feed it with the right code) is a big download, nearly 6 megabytes (for Windows), but the server is fast. The stand alone version is around 3.5 megabytes.
The Install program (Windows) is effective, though there's a point where it asks you where to put the plugins, which is a little ambiguous (just tell it where the Photoshop etc plugins folder lives). The uninstall program is 100% effective, in case you don't like it and don't want to register the program. One point: if you're using the demo and run out of trials, uninstalling and reinstalling won't get you more: it leaves a record somewhere that it checks. So use your trial file saves cautiously.
Enough of the background, how does it work and what does it do?
Well, there are really four programs rolled into one: a digital watermarking utility, a GIF reducer and palette modifier, a JPEG compressor and a dither colour generator. They are all accessed from the main screen, which comes showing the watermark logo - just click on that to access the other actions.
The watermark program embeds information - names, copyright dates, messages etc in the fabric of the file. Useful if you want to stop people pirating your images.
The GIF and JPEG compressors consist of a control area and a viewing area, though you only see the "after" image, not the before and after, and since you can't move the main interface screen off to one side, you can't readily do a comparison between before and after. The file size is also given, along with a hypothetical download time for different modem speeds. Unfortunately the file size is truncated to the nearest tenth of a kilobyte, so you can't tell exactly how small the file is, to judge whether any slight extra compression is worthwhile.
The GIF interface works well, allowing you to alter the red/blue/green levels, image size and dithering level, and to chose you colour depth (though only by number of bits, which restricts you from selecting, say 40 colours - only 32 or 64 can be chosen in that region). The dithering is quite effective. There is also a fringe transparency control to avoid dark or bright areas next to transparent colours.
The JPEG interface is quite unusual, with a lot more control than normal. There are five sliders: an overall or global compression level, a tonal range compression control, a colour compression control, a size selector and a control to select a range of colours for special treatment to avoid compression artifacts.
What do these controls do? The Global control is the standard compression level or quality control. The Tonal Range control uses an averaging process on tonal ranges, which AutoFX claims improves the compression on some images. The Colour compression control allows you to shrink the size of the file by introducing heavier colour compression, or to set the colours at a lower level of compression to retain their intensity. It works very well. The Size control allows you to resize the image. The most unusual control is the Shield Range selector and colour control. You select a particular colour from the image that is likely to display compression artifacts, and you can reduce the level of these artifacts by changing the shield range. An interesting idea, which seems to work on some images.
You can't magnify the image size to inspect compression artifacts, however. File sizes appear to be competitive with the best, though with the demo limit on the number of file saves, I wasn't able to test this thoroughly.
Certainly the JPEG compressor is among the most sophisticated of those I've tried.
Finally, the dither engine: it is different from ColorSafe or Ditherbox, in that it is applied directly to the image, not to a synthetic "fill" colour for later application. As far as I can tell, its purpose is to allow you to modify certain areas in the image that might be affected by dithering on low bit level colour displays, and change them to colours less likely to cause problems. Again, with the limited saving capabilities of the demo, I couldn't explore the effects of this control in much depth.
On top of this, there's a batch control that lets you process numbers of files. I didn't try this because of the demo save limit.
Synopsis? A sophisticated and complex program that requires a bit of learning to use well. The limited number of file saves before the demo expires means you can't really get the hang of it before there's no more room to play. It's an interesting program with a different interface. The stand alone program works well if you don't have Photoshop. This is one program you'll need to try for yourself to judge whether you like it or not. Fair value, considering all the controls you get.
Links to information about web graphics compression, palettes and related matters of interest.
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This information is Copyright © 1997 David Nicholls. These pages may be linked to, provided you don't embed them in frames, but may not be reproduced in any form without permission in writing from the author.