von dp am 17.April 97 um 22:41:18:
zu: palettes, palettes, palettes von dp am 15.Maerz 97 um 17:11:44:
NO WAY! Read this:
Adobe Photoshop is an indispensable program for making images for the
web. But for web designers, it's less than ideal. Let me show you a
problem. If you make a circle in which the most prominent color is a
certain red (say, 205, 53, 21) and you reduce the colors using an
adaptive palette, Photoshop returns a palette in which that same color,
which should be unchanged, has shifted to a very similar, but nonteheless
different, shade of red (in this case 201, 51, 19). This occurs because
Photoshop reduces colors from a 24-bit (8x8x8) color space to a 15-bit
(5x5x5) color space before executing its Median Cut algorythm to find the
best palette. After the reduction, the resulting 15-bit palette gets a
few extra bits tacked on to show the final palette colors as RGB. Those
extra bits cause the color shift you detect, and the color shift causes a
dithered area when displayed on a browser with only 256 colors.
The only colors not affected are the eight at the corners of the color
cube (color cube known to web designers).
Every other color will experience some shift after adaptive color
reduction in Photoshop. If you are in a pinch, you can open the color
table and type in the real values. While this works, it's tedious and no
one should have to do it.
I hope to see solution from Adobe,in the form of a true-color export
plug-in (see the Adobe site). For now, I use Debabelizer to do my final
color reductions, because Debabelizer does not shift colors. See the book
sit (killersites.com) for late breaking news on Photoshop and adaptive
color palettes.
Finally, Photoshop doesn't let the user see the color palette while
viewing the image. I've requested this feature over and over, but Adobe
doesn't have time to do it. As an exercise in interactive product
development, there are forms at the Book Site where you can give your
feedback, which we will forward to various manufacturers.
(from: Creating Killer Web sites, by David Siegel, Hayden Books, ISBN:
1-56830-289-4)
So, Debabelizer rules!
D. Plänitz