5 Replies Latest reply on Feb 9, 2012 12:26 AM by PECourtejoie

    How to reduce number of colors in an image

    erleichda Level 1

      I am fairly new to Photoshop and I'm learning as I go, so I apologize for using your time.  I haven't worked with images that much - I've used MS Digital Image Suite with photos from my camera.  That's the extent of my knowledge.


      I am taking over a job from someone who is gone and I can't ask him how to do this.  He used Photoshop to reduce the number of colors in an image (for example, a color drawing or clipart) to 2-6 colors.  I haven't been able to figure this out.  I've visited this site that explains how to reduce tones but it's still a lot of colors.  I thought I might learn something from this link that explained how to make Photoshop cartoons, but I didn't.  I've done a lot of searching but nothing seems to explain this.  I know that the other guy had some knowledge of Photoshop but he wasn't a power user.


      Thanks to anyone who will help me.  (I am using CS5.)

        • 1. Re: How to reduce number of colors in an image
          c.pfaffenbichler Level 9

          Naturally there are several options for what you are asking – but it also depends on what you really need as end result.

          One possibility might be

          Layer > New Adjustment Layer > Posterize

          Another one would be to create copy of the image and use

          Image > Mode > Indexed Color

          and then edit the Palette (number of colors for example) and Options as needed.

          • 2. Re: How to reduce number of colors in an image
            Trevor.Dennis Adobe Community Professional (Moderator)

            It sounds like you are talking about a cartoon type gif image, and the Indexed colour is definitely the way to do that as above, but if you want to keep it as a jpg then Save for Web is a very useful tool, and you can see what affect it has on file size as you adjust the output options.  But I think you already had the right answer.

            • 3. Re: How to reduce number of colors in an image
              erleichda Level 1

              Sorry I didn't put in more detail.  These are for drawings that belong to me or that I have a license for.  They're png and jpg files but they are not going on the web.  I need to reduce the colors down to no more than 4.  I tried the posterize idea, and earlier today I found a 'Save for web and devices' idea which does something very similar to the Image>Mode>Indexed color idea above, which I just tried  (thanks, c.pf). 


              I don't know what this other guy did (the one I talked about in my first message) but they insist he did it very easily using Photoshop (CS5).  I tried a lot of things before and after I wrote this help message, based on web suggestions.  But I realized with these last two ideas I tried that this can't be done, at least not completely.  In my head, I thought that I would be able to reduce the picture to (for this example) 4 colors of my choosing.  The colors can be any pms color. 


              So, based on your help I found that if the areas were enclosed I could make them black and white and use color fill.  But some of the items aren't one color even though they look like it.  I would have to paint the pixels one color and this would take a long time even if they were enclosed. They tell me he just made these and he didn't have much of a knowledge of Photoshop, either.  But it's looking like it's not that simple.  Thanks again for your help.

              • 4. Re: How to reduce number of colors in an image
                Paulo Skylar Level 4

                It is not clear to me what your issues are with the previous suggestions.


                If you change your image to index color mode, specify 4 colors, force custom colors and select your choice of 4 Pantone colors then it would seem that ALL your criteria are met.  Perhaps you could post an example of an original & modified imaged that the previous designer produced and specify what is wrong with the index color approach, someone might be able to help.



                • 5. Re: How to reduce number of colors in an image
                  PECourtejoie Adobe Community Professional

                  Are you sure that he was using Photoshop? (see my third solution)

                  There are some plug-ins for Photoshop, but they basically do the same as the posterize or index mode: http://www.topazlabs.com/simplify/ (commercial) see this panel for colorizing comic art: http://vimeo.com/user3771002/videos


                  I would rather use posterize, as an adjustment layer, as you can control it.

                  Try with this layer stack, from bottom to top:

                  Convert the original image in a Smart Object, in order to use Smart filters and blur the image (Gaussian Blur, or noise>median or blur>smart blur or blur>surface blur could be interesting internatives) would be useful, to make smoother posterized areas.

                  A dodge/burn layers (a neutral gray layer in overlay mode) to adjust areas using the Dodge/burn tools.

                  the Posterize Adjustment layer, with very few colors

                  On top of it, put a gradient map adjustment layer, to control the posterized colors

                  Vectorizing in Illustrator can also be used to reduce the number of colors. Live Trace: http://help.adobe.com/en_US/illustrator/cs/using/WS714a382cdf7d304e7e07d0100196cbc5f-6229a .html

                  More on the topic: http://help.adobe.com/en_US/illustrator/cs/using/WS714a382cdf7d304e7e07d0100196cbc5f-622aa .html