Index Color - Image Exact

[Joanne Keeler]

I am trying to change a flattened image from RGB to Index and want to use the Exact feature, but it is grayed out and will not let me use it. Can someone tell me what I might be doing wrong. Any help would be greatly appreciated. Thank you.

[Burton Ogden]

Joanne,

On the Indexed Color dialog you didn't say what your choice was in the Palette field, but if it was "Adaptive" you should change your Dither selection (in the Options area) from "None" to "Diffusion". It also might make a difference what version of Photoshop you are using. I am using 5.0.2.

-- Burton --

[dennis johnson]

The "exact" option will only be available if there are fewer than 256 colors in the original image. Converting to indexed color when an image has more than that number of colors will - of necessity - cause some colors to be discarded, thus the conversion cannot be "exact".

[dennis johnson]

The "exact" option will only be available if there are fewer than 256 colors in the original image. Converting to indexed color when an image has more than that number of colors will - of necessity - cause some colors to be discarded, thus the conversion cannot be "exact".

[Burton Ogden]

Dennis,

The "exact" option will only be available if there are fewer than 256
colors in the original image.




That may be true for later versions of Photoshop, but for Photoshop 5.0.2 it isn't. In PS 5.0.2 take an image that you know has more than 256 colors, convert to Indexed and in the Indexed Color dialog choose Palette as Adaptive, Color Depth 8 bits/pixel, Colors 256, change Dither from None to Diffusion (that is crucial), Color Matching can be either Faster or Best, and you can check the Preserve Exact Colors checkbox.

Admittedly this seems a bit illogical and may be a bug in PS 5.0.2. But try it in your version of Photoshop.

-- Burton --

[Chris Cox]

Preserve exact colors doesn' have anything to do with the number of colors -- it has to do with the dithering. You might want to read the manual about the indexed color options....

[dennis johnson]

Burton,

Preserve Exact Colors is not what I was talking about, nor - I believe - is it what Joanne was asking about.

I quote from the Photoshop online Help regarding conversion from RGB to Indexed Color mode (Photoshop 7.01):

"Exact (option) -

Creates a palette using the exact colors appearing in the RGB image--an option available only if the image uses 256 or fewer colors. Because the image's palette contains all colors in the image, there is no dithering."

[Burton Ogden]

Dennis,

Preserve Exact Colors is not what I was talking about, nor - I believe
- is it what Joanne was asking about.




You're probably right. When Joanne said

I am trying to change a flattened image from RGB to Index and want to
use the Exact feature...




she should have said the Exact palette.

-- Burton --