RE: Format of graphics in Word documents

[Fred Ridder <docudoc -at- hotmail -dot- com>]

Sean Brierly wrote (in part):
>    Remember, a GIF is limited to 256 colors, so
> if you test, make sure you test a BMP with 256 colors and a PNG with 256
> colors to the GIF, which cannot have more than 256 colors; all must have
> the same number of pixels, of course.
> 
> IOW, if you embed a PNG in a Word document, and it's 24-bit, then the
> resulting file will be larger than if you had embedded a GIF. Why?
> Because the GIF downsamples the color to 8-bit and you are thus not
> embedding the same image in both cases.
 
This is not exactly correct regarding GIF. Yes, GIF is limited to 256 different
colors, but it does not "downsample the color to 8-bit". GIF uses an indexed
or paletized color scheme, where the 256 most prevalent colors in the original
image (defined to whatever color depth was used in the original image) are 
mapped to 8-bit index numbers. If the original image actually uses more than
256 different colors (common in a photographic image but not necessarily
the case in line art or screen shots unless the image uses graduated fills or
fountains), some of the color values will be mapped to the closest index
color, resulting in some degree of posterization. If the original image actually 
uses fewer than 256 different colors, a GIF version of the image will retain 
full color fidelity.
 
-Fred Ridder
 
 
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