Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt Extensions
  • Unsolved
Collapse
Brand Logo
  1. Home
  2. Qt Development
  3. General and Desktop
  4. Line Tracer/Digitizer
Forum Update on Monday, May 27th 2025

Line Tracer/Digitizer

Scheduled Pinned Locked Moved Unsolved General and Desktop
14 Posts 4 Posters 1.2k Views
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • P ParanoidAndroid

    @mrjj

    I need it to automatically detect the line and plot the points so instead of the user clicking several points on the line they instead click a couple and the program autofills the other points according to the line

    mrjjM Offline
    mrjjM Offline
    mrjj
    Lifetime Qt Champion
    wrote on last edited by mrjj
    #4

    @ParanoidAndroid
    Ok and are those lines straight or more like a spline / curve ?
    if just a line then
    https://www.geeksforgeeks.org/program-find-line-passing-2-points/

    but since you asked for help i assume its something more complicated ?

    P 1 Reply Last reply
    0
    • mrjjM mrjj

      @ParanoidAndroid
      Ok and are those lines straight or more like a spline / curve ?
      if just a line then
      https://www.geeksforgeeks.org/program-find-line-passing-2-points/

      but since you asked for help i assume its something more complicated ?

      P Offline
      P Offline
      ParanoidAndroid
      wrote on last edited by
      #5

      @mrjj They can be any 2D line graph splines, straight, lines curves

      mrjjM 1 Reply Last reply
      0
      • P ParanoidAndroid

        @mrjj They can be any 2D line graph splines, straight, lines curves

        mrjjM Offline
        mrjjM Offline
        mrjj
        Lifetime Qt Champion
        wrote on last edited by
        #6

        @ParanoidAndroid
        Ok. so we need the data these
        2D line graph splines, straight, lines curves are based on if we are to calculate its
        function based on a few points.

        Can i see one images with the drawn curves you wish to calculate ?

        1 Reply Last reply
        0
        • P Offline
          P Offline
          ParanoidAndroid
          wrote on last edited by
          #7

          Here is an example of the splineGraph3.png

          1 Reply Last reply
          0
          • kshegunovK Offline
            kshegunovK Offline
            kshegunov
            Moderators
            wrote on last edited by
            #8

            You need to read math, I'm afraid. Rational B-splines, normal cubic splines or polyharmonic splines could work in your case, however I leave the wikipedia-ing to you. ;)

            Read and abide by the Qt Code of Conduct

            P 1 Reply Last reply
            3
            • kshegunovK kshegunov

              You need to read math, I'm afraid. Rational B-splines, normal cubic splines or polyharmonic splines could work in your case, however I leave the wikipedia-ing to you. ;)

              P Offline
              P Offline
              ParanoidAndroid
              wrote on last edited by
              #9

              @kshegunov
              Is there no way to say track the colour of the spline and give pixel coordinates

              kshegunovK 1 Reply Last reply
              0
              • P ParanoidAndroid

                @kshegunov
                Is there no way to say track the colour of the spline and give pixel coordinates

                kshegunovK Offline
                kshegunovK Offline
                kshegunov
                Moderators
                wrote on last edited by
                #10

                Sorry, I don't understand the question. Please rephrase.

                Read and abide by the Qt Code of Conduct

                P 1 Reply Last reply
                0
                • kshegunovK kshegunov

                  Sorry, I don't understand the question. Please rephrase.

                  P Offline
                  P Offline
                  ParanoidAndroid
                  wrote on last edited by
                  #11

                  @kshegunov instead of using mathematics could you say click to select the colour of the line and then have the application give the coordinates of every pixel connected with that colour

                  mrjjM 1 Reply Last reply
                  0
                  • P ParanoidAndroid

                    @kshegunov instead of using mathematics could you say click to select the colour of the line and then have the application give the coordinates of every pixel connected with that colour

                    mrjjM Offline
                    mrjjM Offline
                    mrjj
                    Lifetime Qt Champion
                    wrote on last edited by
                    #12

                    @ParanoidAndroid
                    Hi
                    If all images are as clean as this, you can easily scan to find the blue color and hence the Y coordinate.
                    https://doc.qt.io/qt-5/qimage.html#pixel-1
                    or the faster way
                    https://doc.qt.io/qt-5/qimage.html#scanLine

                    But it wont be fast as such but unless
                    tiny mini board it should be fine:)

                    P 1 Reply Last reply
                    1
                    • mrjjM mrjj

                      @ParanoidAndroid
                      Hi
                      If all images are as clean as this, you can easily scan to find the blue color and hence the Y coordinate.
                      https://doc.qt.io/qt-5/qimage.html#pixel-1
                      or the faster way
                      https://doc.qt.io/qt-5/qimage.html#scanLine

                      But it wont be fast as such but unless
                      tiny mini board it should be fine:)

                      P Offline
                      P Offline
                      ParanoidAndroid
                      wrote on last edited by
                      #13

                      @mrjj thankyou for your help. Will this give an x coordinate aswell

                      jsulmJ 1 Reply Last reply
                      0
                      • P ParanoidAndroid

                        @mrjj thankyou for your help. Will this give an x coordinate aswell

                        jsulmJ Offline
                        jsulmJ Offline
                        jsulm
                        Lifetime Qt Champion
                        wrote on last edited by
                        #14

                        @ParanoidAndroid said in Line Tracer/Digitizer:

                        Will this give an x coordinate aswell

                        Just iterate over all x coordinates and search for y like @mrjj suggested. Or iterate over y and get x...

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

                        1 Reply Last reply
                        0

                        • Login

                        • Login or register to search.
                        • First post
                          Last post
                        0
                        • Categories
                        • Recent
                        • Tags
                        • Popular
                        • Users
                        • Groups
                        • Search
                        • Get Qt Extensions
                        • Unsolved