6 Replies Latest reply on Nov 19, 2012 6:30 AM by rob day

    Color match area

    luca del carlo Newcomer

      I have a B&W pic I'd like to sum the overall grayscale values into one number and create a swatch from this. How would one do this?

        • 1. Re: Color match area
          [Jongware] Mythic

          With Photoshop, perhaps. Blur-and-blur-some-more until your image is all but a gray blur. Then measure it.

          • 2. Re: Color match area
            rob day Rockstar

            PhotoShop's Histogram panel in expanded view gives the median pixel value. So in this case it would be 100|100|100 RGB:


            Screen shot 2012-11-19 at 8.06.28 AM.png

            • 3. Re: Color match area
              [Jongware] Mythic

              It shows a value "100", so I'm guessing this is not a percentage . So this must be in 1/256ths? Or, if the maximum value for all-white is "255", 1/255ths?


              Wait -- that cannot be right, I just called up a simple graphic (black lines on white background) and it shows "255". Maybe you should look at the "Mean" value, 2 items up? Statistics is one of the few fields of maths in which I'm surprisingly bad, I could not recall the difference between Mean, StdDev, and Median if my life depended on it ...

              • 4. Re: Color match area
                rob day Rockstar

                You're right Mean is the average.

                • 5. Re: Color match area
                  [Jongware] Mythic

                  <g> I tried my blur/blur/blur/and blur even more, but it doesn't lead to anything useful after all.


                  Since the Mean is "109.88" in your image, I suspect this isn't a percentage either If it is 1/256ths, there still is a lingering question ... Luca wants a grayscale swatch, which is measured as a percentage of [Black], that is, 0% is white and 100% is full black.


                  So would the value needed be 109.88/256 * 100% = 42.9% [Black] or does Photoshop measure "the other way around", as usual for RGB, and is the value of Black therefore 100 - 42.9 = 57.1%?

                  • 6. Re: Color match area
                    rob day Rockstar

                    Black therefore 100 - 42.9 = 57.1%?


                    I think that's probably right. Photoshop's Curve dialog lets you choose between 8-bits and ink percentage:


                    Screen shot 2012-11-19 at 9.26.57 AM.png


                    Screen shot 2012-11-19 at 9.27.05 AM.png