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C4003 - How do I avoid palette problems?

by - Joseph Ganci

I am having to work with several images. I scanned them as RGB images, indexed the color to take them to 8 bit and they look good while in Photoshop, but go to hell in A3W - banding, etc. How do I avoid this? 

If in Photoshop you index the graphic to 8-bit System palette and not to a custom or adaptive palette, this should fix your problem.  I've never had a problem doing this when I've had a ton of differing graphics. 

The alternative is to dither them all to one nonsystem palette.  While the system palette has a good mix of colors, it isn't ideal if you are doing a course on say, oceanography and have a lot of greens and blues in your photos.  In that case, it's better to use Debabelizer or Photoshop to create a superpalette from all of your photos and then use that in Authorware.  You can apply this palette through the Modify, File, Palette setup menu.   

The best thing is to stick with one palette in Authorware, and all of your images to be saved in that palette.  The most useful one is System for this purpose. 

If you must use more than one palette because your graphics and photos are so diverse in their color makeup, you'll need to use the SetPalette UCD or U32 that comes with Authorware on the Windows side and the SetPalette XCMD on the Macintosh side every time you want to change the palette.  Authorware also comes with an example file.  Unfortunately, every time you do this, you will see a screen flash. 

Here's how to avoid this problem. If you can, make sure that several colors in each of your palettes are identical in location. Then, before you change palettes, make sure that whatever colors you have on the screen come only from those colors that are identical in each palette (or at least in the one just before and after your palette change). 

Since most palettes keep the pure black color (where RGB = 0, 0, 0) and pure white color (where RGB = 255, 255, 255) located in the same places, you can usually safely have a screen that is composed of only black and white pixels while performing a palette change.  Note that this is not usually done since it leaves little leeway in screen design.  Most authors end up "fading" to a black or white screen between palette changes to avoid the palette flash.  This is hardly ever recommended for training or educational applications, since you don't want the screen fading out during a lesson.  For kiosk application, however, this is sometimes acceptable. 

To wrap up, it's best to stick to one palette if at all possible. Go to our Download Area to download the Indeo Multimedia palette, which is excllent when you're using digital video in your files.

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