A bug & note on using .png graphics....

[Combs, Richard]

Art Campbell wrote:  
 
> I think we're using slightly different terms when describing 
> the same files.
> In photos/photoshop, an 8-bit depth means 8 bits of red, 
> green, and blue info. 16 million shades (256X256X256). Which 
<snip> 
> The color definition thing is really wierd. I never saw that 
> happen before.
> Odd that it only seems to be png. I can see it being useful 
> though if you have to color-match something in a layout to a 
> graphic color, but it's still really odd that it'd pop up 
> here. And it'd certainly add to file bloat.
> 
> Makes me wonder if the crash was happening because the number 
> of colors exceeded a maximum number in the file....

Like I said, I'm no expert, but I've never heard the term "8-bit" used
to describe an image that uses 24 bits to define each pixel, and I'd be
very surprised if Photoshop uses the term that way. 

Color depth is generally specified as "bits per pixel (bpp)" -- see this
Wikipedia topic: 

http://en.wikipedia.org/wiki/Color_depth 

It describes indexed color of various bit depths, including: 

"8-bit color (2^8 = 256 colors) VGA at low resolution, Super VGA"

And it contains this Truecolor definition:

"24-bit Truecolor uses 8 bits to represent red, 8 bits to represent
blue, and 8 bits to represent green. 2^8 = 256 levels of each of these
three colors can therefore be combined to give a total of 16,777,216
mixed colors (256 x 256 x 256)."

As for the RGB color definitions, I'm confused as to whether your files
have them or not. Do you see hundreds of color definitions of the form
"RGB 000, 082, 044"? If so, there are (or were) palettized 256-color PNG
graphics in the FM doc. AFAIK, that's the only place from which they can
come. 

If all your PNGs are/were 16-million-color files, you shouldn't have
hundreds of defined RGB colors in the doc. 

Richard


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Richard G. Combs
Senior Technical Writer
Polycom, Inc.
richardDOTcombs AT polycomDOTcom
303-223-5111
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rgcombs AT gmailDOTcom
303-777-0436
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