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First steps towards a new adjustment tool

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  • #16
    Re: First steps towards a new adjustment tool

    Black and white shoe is easy. What about colored shoe? Every part of it has not only value, but also hue and saturation. Also highlight of a black shoe would be white, how would you tell the mid point, from which nothing should be changed? White should stay white. Also output depends on input. If you target image slightly different from reference, it would look different even if you get numbers perfectly right.

    People asking "how to" because they don't know, not because they don't have tools.
    Last edited by Tulack; 06-25-2015, 03:32 PM.

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    • #17
      Re: First steps towards a new adjustment tool

      Originally posted by pixaeiro View Post
      That would be awesome! Thanks!
      See Erik Reinhard's site for one. I own one of his books, and he's an excellent writer. Most of his papers are reachable from that link. Francoise Pitie did some interesting work, treating pixel level transitions as a probability density function.

      fast local color transfer via dominant colors mapping

      I can't find an unprivileged link for Xiao and Ma. It provides some of the earlier work in gradient preserving mappings. The ones above are more digestible anyway. It's also worth reviewing the wiki on the LMS color space, which is frequently used for reference in examining methods of decomposing an image into visually orthogonal channels. If you're interested in the segmentation aspects, google soft scissors or poisson image editing (poisson's equation in case you're interested).

      There are some books that might also help here, but anything really helpful won't be elementary reading.Others have attempted it in commercial products with my favorite being VSCO.

      If you're interested in more fundamental books about color, see Wyzecki and Stiles, Mark Fairchilds, Noboru Ohta, Jan Morovic. For basic implementations of open source color engines, see littleCMS or ArgyllCMS. I'm not digging up links on each book, but I would suggest you try an academic library. The books are otherwise quite expensive. Wyzecki and Stiles is really a hardcore science book used primarily for reference. The papers also sometimes refer to math texts when explaining the breakdown of their algorithms. They don't do this with anything elementary, including probability. Anything I link there is going to be fairly hardcore.

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      • #18
        Re: First steps towards a new adjustment tool

        Originally posted by Tulack View Post
        Black and white shoe is easy. What about colored shoe? Every part of it has not only value, but also hue and saturation. Also highlight of a black shoe would be white, how would you tell the mid point, from which nothing should be changed? White should stay white. Also output depends on input. If you target image slightly different from reference, it would look different even if you get numbers perfectly right.

        People asking "how to" because they don't know, not because they don't have tools.
        I sometimes wonder how you reach these conclusions. You are veering into technical areas rather than artistic ones, and it's a bad idea.

        Methods of automating a match relative to some metric have been attempted due to the labor cost of something which is ultimately tedious. Further hue, saturation, and value aren't completely decoupled in terms of human vision. A more modern way of looking at this would be one of examining cone response under a standardized model, as we can't completely control for visual processing. See LMS for one. I started to expand on that, but it's just too much material for a given post. The point was that yes there has been progress in automated variations on this. I linked one commercialized example in the previous post. That you can achieve the same thing today is irrelevant. I've altered colors by hand with various layers, masks, channel mixer, retinting bright reflections, etc. No one denied that was possible.

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        • #19
          Re: First steps towards a new adjustment tool

          Did a quick & dirty test just to see if I understand the problem. I didn't use curves, and the results aren't perfect, but is this similar to the desired goal?

          (The results are posterized, but I think I can take care of that.)
          Attached Files

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          • #20
            Re: First steps towards a new adjustment tool

            It's a step, but hue tools already exist. Can it remap luminosity, or just color?
            Learn by teaching
            Take responsibility for learning

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            • #21
              Re: First steps towards a new adjustment tool

              Basically what I did:

              -find optimal 16 color palette in source image, sort by luminosity, stretch palette to 256 colors (could be more)
              -map colors to the destination image via RGB distance (r * r + g * g + b * b)

              So it's mapping color, but in an averaged out way. I'm not sure I fully understand the problem yet, but perhaps the goal is to make the destination image's histogram similar to that of the source image?

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              • #22
                Re: First steps towards a new adjustment tool

                Funny you should mention histograms. My first iteration of this idea I pitched directly to Adobe, as a histogram matching tool. But it was quickly demonstrated to me that this is a poor way to approach this. At the time I fought it, but I've since come to agree.

                Which is why I brought up the Premiere tool several posts up, as adding location to histogram seems like a plausible direction. But it only made things more confused.
                Learn by teaching
                Take responsibility for learning

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                • #23
                  Re: First steps towards a new adjustment tool

                  If L/M/D means light/medium/dark:

                  Code:
                  1st image:
                  |LLLLLLLLLLLLLLLL|MMMMMMMM|DDDDDDDD|
                  
                  2nd image:
                  |LLLLLL|MMMMMMMMMMMMMM|DDDDDDDDDDDD|
                  Pretend dragging the split marks in the second image to match the first.

                  Is this the idea?

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                  • #24
                    Re: First steps towards a new adjustment tool

                    Originally posted by Doug Nelson View Post
                    Funny you should mention histograms. My first iteration of this idea I pitched directly to Adobe, as a histogram matching tool. But it was quickly demonstrated to me that this is a poor way to approach this. At the time I fought it, but I've since come to agree.

                    Which is why I brought up the Premiere tool several posts up, as adding location to histogram seems like a plausible direction. But it only made things more confused.
                    It was also done more than a decade ago. You pitched them something they were well aware of and had probably tested internally. In fact that's one of the papers I didn't link (because it sucks). The naive approach was to match both mean and median.

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