Microsoft KB Archive/133173

PUB3: Why Some Objects Dither with 256-Color Video

= PUB3: Why Some Objects Dither with 256-Color Video =

Q133173
- The information in this article applies to:

- Microsoft Publisher for Windows 95, version 3.0 - Microsoft Publisher 97 -

SUMMARY

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If you run Publisher while your display is configured for 256 colors, many different objects will appear dithered. If you open the same publication when your display is configured for 32,000 or more colors, the same objects display without dithering.

Dithering is the process of simulating one color by breaking it up into a pattern of dots of different colors.

These types of objects may dither when displayed at a color depth of 256 colors:

- Imported graphics - OLE objects - Recolored pictures - Publisher drawing objects filled with tints, shades, or gradients

These types of objects will not dither when displayed at a color depth of 256 colors:

- Text - Single-pixel thick lines - Publisher drawing objects filled with any color in the Colors dialog box with the Basic Colors button selected

MORE INFORMATION

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Many Windows 95 programs have a fixed palette of 256 nondithering colors to use when Windows 95 is running with a display configured for 256 colors. Publisher is one of these.

When Publisher renders an object to the display driver, it determines whether the video driver should display that object using one of the colors on the palette or using the best approximation of the actual color through dithering.

The objects that Publisher does not dither are those objects that become hard to use if they are dithered. Dithered text, for example, is often very difficult to read.

The types of objects that Publisher allows to dither are those objects that suffer visually if their colors are changed too much--for example, if you have an object that has a gradient fill from light-blue to black. The standard 256 color palette may only have two or three shades between light blue and black, which is not enough to display a nice gradient. In this case, a dithered gradient gives a better approximation of what the object will look like when you print it.

For the same reason, it would be difficult to tell the difference between a tint of 10-percent yellow and a tint of 2-percent yellow using the standard palette. Dithering these tints makes it possible to visually identify and compare objects filled with these colors.

If you change your Windows 95 display settings to a color depth of High Color 15-bit (32,768 colors), High Color 16-bit (65,536 colors), or True Color (16,777,216 colors), Publisher won't use its palette, and no objects will dither.

You cannot modify the algorithm Publisher uses to decide which object to dither and which to display as pure colors.

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