PPT2000: Semi-Transparent PNG Images Appear Dithered in PowerPoint (212420)
The information in this article applies to:
- Microsoft PowerPoint 2000
This article was previously published under Q212420 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.
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 composting 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
wine glass 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 import a picture that contains transparency information,
PowerPoint generates a mask, which substitutes the slide background for the
masked pixels. This mask is not semi-transparent; it either shows or hides
(masks) a pixel. To simulate semi-transparency, PowerPoint generates a mask
that hides alternate pixels in a semi-transparent area.
NOTE: These images will display with a higher level of fidelity during the slide show.
| Modification Type: | Major | Last Reviewed: | 6/15/2001 |
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| Keywords: | kbdraw kbinfo KB212420 |
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