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11010 - Authorware Bitmap Optimization

by - Dietrich Schultz (former Authorware engineer)

Article appears courtesy of Danny Engelman’s Gems and Jewels of the AWARE list

I've got some questions regarding the Bitmap Optimization feature of Authorware.

My understanding is that this causes a second palette to be created for each 8-bit graphic in the file, and when the program is run in 8-bit, this second palette is used so that Authorware doesn't have to re-index images on the fly.

Correct. Note that this optimization really only matters under Win 3.1. My tests have shown that the optimization (or lack thereof) makes no difference under Windows 95--ie. it's always fast. It may just be the video cards I've tested, but so far it's been that way on all cards I've tried which leads to be believe that GDI was made much smarter in Win 95.

My question concerns the use of the SetPalette function. The TechNote (#3046) for this says that using SetPalette "will nullify any performance gains from bitmaps that have previously been optimized through Authorware. Does this mean that these performance gains are only nullified while the new palette is being used?


>And will it make a difference how I return to my default palette? That is, should I use SetPalette or ResetPalette to restore it?

I'm not sure. If you can use SetPalette it would have to be exactly the right palette.

>Also, if all graphics in a program have the same palette applied, and it is that palette that has been loaded into Authorware, is there any reason to use the Bitmap Optimization function?

Authorware automatically creates the second, indexed palette whenever you edit a display icon so if you loaded the course palette before creating the displays then everything will already be optimized anyway.

And finally, when I am creating an custom palette for my Authorware programs, should I create a palette of only 236 colors so that I can use the Preserve System Colors checkbox in Authorware without having to worry about my custom palette losing any colors? Or is it safe to create a custom palette with all 256 colors, with 20 of those colors being the system colors, and still use the Preserve System Colors checkbox? According to the TechNote, Authorware tosses out any colors that are the same as the System Colors, then adds them back in. I assume, then, that I SHOULD use Bitmap Optimization in this case, especially if the system colors in my custom palette were not in the same locations as the system colors in the Preserve-System-Colors palette created by Authorware.

Just use optimization all the time. There's really no reason not to. At worst it will have no effect (ie. if the runtime palette doesn't match the stored, "optimized" palette) and usually it will make the bitmaps draw faster.

Dietrich Schultz

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