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QImage reduce color to nearest indexed palette

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  • Shadowblitz16S Shadowblitz16

    thankyou so much kshegunov I will take a look at this.
    however I see that you use the boost library and I seem to not have it.
    can you explain where to get it?

    jsulmJ Offline
    jsulmJ Offline
    jsulm
    Lifetime Qt Champion
    wrote on last edited by
    #7

    @Shadowblitz16 For which platform, OS and compiler?

    https://forum.qt.io/topic/113070/qt-code-of-conduct

    1 Reply Last reply
    0
    • Shadowblitz16S Shadowblitz16

      thankyou so much kshegunov I will take a look at this.
      however I see that you use the boost library and I seem to not have it.
      can you explain where to get it?

      kshegunovK Offline
      kshegunovK Offline
      kshegunov
      Moderators
      wrote on last edited by kshegunov
      #8

      @Shadowblitz16 said in Convert Image to Array based pixel data?:

      however I see that you use the boost library and I seem to not have it.
      can you explain where to get it?

      http://www.boost.org/

      Note that I use only the statistics framework (header-only) so you don't need to compile anything before hand. You just need to point your project file to the boost directory (through the INCLUDEPATH variable). Also, since I only use the min, max and mean accumulator extractors from that library you can simply provide your own implementations and not care about including boost at all.

      Read and abide by the Qt Code of Conduct

      1 Reply Last reply
      2
      • Shadowblitz16S Offline
        Shadowblitz16S Offline
        Shadowblitz16
        wrote on last edited by
        #9

        Thankyou kshegunov I will do that

        1 Reply Last reply
        0
        • Shadowblitz16S Offline
          Shadowblitz16S Offline
          Shadowblitz16
          wrote on last edited by Shadowblitz16
          #10

          @kshegunov I'm not sure if this does what I want.

          I'm trying to make my game draw things from pixel data not convert them back into indexed images.

          this way I can store the tiledata directly into a json file representing the tiles and there index
          here is an example json explaining what format I want my tiles in

          {
          	"TILES": [
          		[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
          		[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
          	  	...all the way to 65535...
          		[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
          	]
          }
          

          EDIT: here is what I got for a loading function so far

          QImage TileTable::load_image(QString file, int tilewidth, int tileheight)
          {
              QImage image(file);
              image.convertToFormat(QImage::Format_RGB444);
          
              char data[65536]; // need a 2d array here later
              int  len = (image.width / tilewidth) * (image.height / tileheight);
          
              for(int i=0; i<len; i++)
              {
                  int x = i % tile_width;
                  int y = i / tile_height;
                  QImage subImage = image.copy(x,y,tilw_width, tile_height);
                  
                  //Todo convert subImage to to array of palette indexes
                  
                  data[i] = subImage; //temparary I want to eventully store a array of indexed pixels here
              }
          }
          

          I just need a way of converting the image

          kshegunovK 1 Reply Last reply
          0
          • Shadowblitz16S Shadowblitz16

            @kshegunov I'm not sure if this does what I want.

            I'm trying to make my game draw things from pixel data not convert them back into indexed images.

            this way I can store the tiledata directly into a json file representing the tiles and there index
            here is an example json explaining what format I want my tiles in

            {
            	"TILES": [
            		[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
            		[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
            	  	...all the way to 65535...
            		[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
            	]
            }
            

            EDIT: here is what I got for a loading function so far

            QImage TileTable::load_image(QString file, int tilewidth, int tileheight)
            {
                QImage image(file);
                image.convertToFormat(QImage::Format_RGB444);
            
                char data[65536]; // need a 2d array here later
                int  len = (image.width / tilewidth) * (image.height / tileheight);
            
                for(int i=0; i<len; i++)
                {
                    int x = i % tile_width;
                    int y = i / tile_height;
                    QImage subImage = image.copy(x,y,tilw_width, tile_height);
                    
                    //Todo convert subImage to to array of palette indexes
                    
                    data[i] = subImage; //temparary I want to eventully store a array of indexed pixels here
                }
            }
            

            I just need a way of converting the image

            kshegunovK Offline
            kshegunovK Offline
            kshegunov
            Moderators
            wrote on last edited by kshegunov
            #11

            Well, I have provided sample code for the conversion. If you don't want to save the data back to an image, you need to modify the code and save the index in an array, but I don't really see a big difference so should be easy to adapt.
            Instead of setPixelColor used here you just save the index of the palette color in your array, should be as simple as this.

            Read and abide by the Qt Code of Conduct

            1 Reply Last reply
            1
            • Shadowblitz16S Offline
              Shadowblitz16S Offline
              Shadowblitz16
              wrote on last edited by
              #12

              @kshegunov I see you didn't use the QImage.bits() method like i did can you explain why?

              kshegunovK 1 Reply Last reply
              0
              • Shadowblitz16S Shadowblitz16

                @kshegunov I see you didn't use the QImage.bits() method like i did can you explain why?

                kshegunovK Offline
                kshegunovK Offline
                kshegunov
                Moderators
                wrote on last edited by kshegunov
                #13

                QImage::bits returns internal data, thus it requires me to know what is the image's format and data padding (if any). Using the pixel modification API does not, on the other hand. Moreover, as this all boils down to interpolation in RGB space, having a color value represented in other color spaces isn't as useful, because the "finding closest" approximation requires a bit more work. For example if I used CMYK I'd have to use 4D color space, if I were to work in HSV I'd have to calculate distances in cylindrical coordinate system, which while possible makes it more complicated for no good reason.

                Read and abide by the Qt Code of Conduct

                1 Reply Last reply
                2
                • Shadowblitz16S Offline
                  Shadowblitz16S Offline
                  Shadowblitz16
                  wrote on last edited by
                  #14

                  thankyou kshegunov however when I add an image and try to reduce its color by lowering the color count it doesn't do anything can you explain why?

                  kshegunovK 1 Reply Last reply
                  0
                  • Shadowblitz16S Shadowblitz16

                    thankyou kshegunov however when I add an image and try to reduce its color by lowering the color count it doesn't do anything can you explain why?

                    kshegunovK Offline
                    kshegunovK Offline
                    kshegunov
                    Moderators
                    wrote on last edited by
                    #15

                    You mean for my toy application?
                    The color count should be a power of two, so 16, 32, 64, 128 are valid, but not say 3, 9, 11.

                    Read and abide by the Qt Code of Conduct

                    1 Reply Last reply
                    0
                    • Shadowblitz16S Offline
                      Shadowblitz16S Offline
                      Shadowblitz16
                      wrote on last edited by
                      #16

                      oh I see why its called color reduction now...
                      it doesn't index the image it just reduces the color..

                      kshegunovK 1 Reply Last reply
                      0
                      • Shadowblitz16S Shadowblitz16

                        oh I see why its called color reduction now...
                        it doesn't index the image it just reduces the color..

                        kshegunovK Offline
                        kshegunovK Offline
                        kshegunov
                        Moderators
                        wrote on last edited by
                        #17

                        @Shadowblitz16 said in QImage reduce color to nearest indexed palette:

                        it doesn't index the image it just reduces the color..

                        I don't follow, what's the difference?
                        An index-colored image is a table of colors (again 8, 16, 32 etc. in number) and instead of assigning RGB values directly to the pixels you assign them indices from that table. My toy app does the table, but instead of saving the table and using index-colored format it just uses the colors directly, but it's basically the same principle. If you open the image histogram you'll see only that number of colors that would otherwise be in the color table.

                        Read and abide by the Qt Code of Conduct

                        1 Reply Last reply
                        0
                        • Shadowblitz16S Offline
                          Shadowblitz16S Offline
                          Shadowblitz16
                          wrote on last edited by
                          #18

                          but it should round the colors to the nearest color on the palette if the palette size isn't big enough to hold all the colors.

                          kshegunovK 1 Reply Last reply
                          0
                          • Shadowblitz16S Shadowblitz16

                            but it should round the colors to the nearest color on the palette if the palette size isn't big enough to hold all the colors.

                            kshegunovK Offline
                            kshegunovK Offline
                            kshegunov
                            Moderators
                            wrote on last edited by kshegunov
                            #19

                            It does - here

                            Read and abide by the Qt Code of Conduct

                            1 Reply Last reply
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                            • Shadowblitz16S Offline
                              Shadowblitz16S Offline
                              Shadowblitz16
                              wrote on last edited by Shadowblitz16
                              #20

                              hmm its not doing it for me.. for example I gave it an image and specified a palette size of 4.
                              after it was done processing it just recolored parts of the image..

                              EDIT: now it doesn't look like its doing anything.

                              EDIT2: ok so when I open the file browser to load an image, all my images are listed as paint.net images when they are not.
                              I think its getting the file extension confused with the default program that opens the file.

                              kshegunovK 1 Reply Last reply
                              0
                              • Shadowblitz16S Shadowblitz16

                                hmm its not doing it for me.. for example I gave it an image and specified a palette size of 4.
                                after it was done processing it just recolored parts of the image..

                                EDIT: now it doesn't look like its doing anything.

                                EDIT2: ok so when I open the file browser to load an image, all my images are listed as paint.net images when they are not.
                                I think its getting the file extension confused with the default program that opens the file.

                                kshegunovK Offline
                                kshegunovK Offline
                                kshegunov
                                Moderators
                                wrote on last edited by
                                #21

                                @Shadowblitz16 said in QImage reduce color to nearest indexed palette:

                                hmm its not doing it for me.. for example I gave it an image and specified a palette size of 4.
                                after it was done processing it just recolored parts of the image..

                                What do you suppose an index based image is to look like?
                                Open any image, put it in photoshop, gimp or w/e make it index-based with a palette size of 4 and observe what happens.

                                Read and abide by the Qt Code of Conduct

                                1 Reply Last reply
                                1
                                • mrjjM Offline
                                  mrjjM Offline
                                  mrjj
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #22

                                  Hi
                                  Unless you use Dithering, a palette of 4 color will destroy most images :)
                                  ![alt text](0_1493897430493_upload-216d44af-ee00-457b-b63b-636f672371d1 image url)

                                  1 Reply Last reply
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