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Palettes


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Rainalkar

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Is it possible to make out which colors in an 8 bit palette are not (or vice versa) part of the picture to which the palette is associated to? If not in Photoshop, perhaps someone knows some other way? It's really important to me.

Thank you very much in advance
 
If I got it right just the first thing that came to mind:
Change color table to Grayscale, create Threshold layer. Now in the Threshold dialog start from level one and go up one by one pressing Up arrow, meanwhile looking at the Histogram panel. Those levels that DO NOT change stats in Histogram panel are missing gray levels in your image corresponding to the indexes оf the unused colors in your pallete.
 
The palette consists of 256 different colors, however, I am sure that not all of them are used. I need to either find out which colors are (un)used.
 
You are probably going to want a script to analyze the image. As far as doing that with standard means, it is an interesting problem, but I can only seem to come up with really complicated means of figuring out the result you want. Someone may know a quicker answer. In years of troubleshooting, my experience has taught me that those asking the questions are not always asking the right ones. Can you tell me what it is you are trying to accomplish? There may be a different, easier solution.
 
Oh, if you want to find out which colors are USED then just turn the image to RGB mode and then again to Indexed, this time choosing Exact for pallete. Open Image->Color table... There you have it! Only colors that are used.
 
That works great, thanks. Now, the last thing - if it could be possible: the system with switching from RGB back to Indexed does produce the colors used, placing them on positions 1,2,3... in the palette. This just crossed my mind, I think it's very complicated, but maybe you could know: is it possible to do the similar, however in a way that it would produce the new palette retaining the positions of the used colors, while switching every unused palette color with some other. Example: a picture contains red, blue, green colors. Their positions in the palette, which is full of other unusedcolors, are (1,3), (3,2), (5,5). Is it possible to automatically alter the palette so that red, blue, green colors retain their positions in the palette, but all other colors are replaced with some other, like white?

Thank you very much for your answers so far
 
It would make things much easier if you tell why did you want it in the first place. As for now it sounds like some very uncommon task.
 
That worked great, now I have another issue... I have pictures, 50+, all in 8-bit color and all using the same palette. Is it possible to find out which colors are used in all of the pictures combined?

I now know how to do this for each picture, but since there are many colors used in many pictures I cannot really compare palettes for each picture to see which colors overlap - that would take me untill Christmas.
 
I will try to explain, albeit my non native English: I have 50+ pictures which use the same, entirely used up palette. However, I KNOW that some colors in that palette are unused in neither picture. I need to alter some of those pictures by using additional colors that are not part of the original palette, but the resulting palette must afterwards be applied to all of the pictures. So, ideally, if I knew which colors are unused in ANY picture, I would just replace those colors with the ones I need.

Could you help me in detail with Imageready, I never really used it? What did you have in mind? Thanks
 
There is a master pallete in Image Ready which combines all the pictures to one pallete. Really not sure you want the very same thing, but seems to me that is what you want. (It's pretty hard to get it given your posts, you know, but I try my best)
 
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