PPT97: Semi-Transparent PNG Images Appear Dithered in PowerPoint (172565)
The information in this article applies to:
- Microsoft PowerPoint 97 for Windows
This article was previously published under Q172565 SUMMARY
If you insert a Portable Network Graphic (PNG) image in a PowerPoint slide,
any semi-transparent portions of the image appear grainy (dithered). If you
examine the image closely, the semi-transparent areas of the picture appear
to be drawn by alternating pixels of the foreground color with pixels of
the slide background color.
NOTE: You only see this effect when you view the graphics in Slide or Notes
view. When you run the slide show, the graphics appear without dithering.
MORE INFORMATION
A PNG file is a type of bitmap. In other words, the picture data is stored
as a rectangular array of dots of different colors. Each dot is described
as a mixture of 256 shades of red, 256 shades of green, 256 shades of blue,
and (optionally) 256 shades of transparency. The transparency component is
called an alpha channel.
If you import semi-transparent images into a photo compositing program
(such as Microsoft Image Composer), you can layer them to achieve various
special effects. For example, if you place the image of a semi-transparent
wineglass filled with red wine in front of the image of a gift box, you can
still see the gift box through the wine. It just has a red tint to it.
When you are in Slide view or Notes view, PowerPoint tries to improve
performance by using a coarser preview of the graphic. When you actually
run the slide show, PowerPoint displays the graphic at full fidelity.
Modification Type: | Major | Last Reviewed: | 11/9/2000 |
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Keywords: | kbdraw kbinfo KB172565 |
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