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Cross compile OpenCV to a RaspberryPI

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  • Kent-DorfmanK Offline
    Kent-DorfmanK Offline
    Kent-Dorfman
    wrote on last edited by
    #2
    This post is deleted!
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    • hamzaelaziziH hamzaelazizi

      Hello, i've been trying to make an application that combines Qt and OpenCV, and then deploy this application on a RaspberryPi.
      i managed to cross compile Qt to run applications i built on my host machine on the RaspberryPi but whenever i want to use OpenCV with it, i fail to get to work. The first time i had incompatible libraries with ARM (they were x86-64) and now when i installed ARM version of OpenCV i get this error in Qt Creator (cannot find -lm).
      Can u please tell me how to cross compile OpenCV as well ? Thank you

      jsulmJ Offline
      jsulmJ Offline
      jsulm
      Lifetime Qt Champion
      wrote on last edited by
      #3

      @hamzaelazizi said in Cross compile OpenCV to a RaspberryPI:

      Can u please tell me how to cross compile OpenCV as well ?

      Why don't you simply install OpenCV packages (including dev packages) on your RaspberryPi (using apt) and then symply sync your sysroot?

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

      hamzaelaziziH 1 Reply Last reply
      0
      • jsulmJ jsulm

        @hamzaelazizi said in Cross compile OpenCV to a RaspberryPI:

        Can u please tell me how to cross compile OpenCV as well ?

        Why don't you simply install OpenCV packages (including dev packages) on your RaspberryPi (using apt) and then symply sync your sysroot?

        hamzaelaziziH Offline
        hamzaelaziziH Offline
        hamzaelazizi
        wrote on last edited by
        #4

        @jsulm May i ask how do i sync my sysroot exactly because i've already installed OpenCV in my RaspberryPi

        jsulmJ 1 Reply Last reply
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        • hamzaelaziziH hamzaelazizi

          @jsulm May i ask how do i sync my sysroot exactly because i've already installed OpenCV in my RaspberryPi

          jsulmJ Offline
          jsulmJ Offline
          jsulm
          Lifetime Qt Champion
          wrote on last edited by
          #5

          @hamzaelazizi Depends on how you created it. There are different ways. For example you can simply connect the SD card from your RaspberryPi to your development machine. Or you can copy the /usr content (at least lib and include subfolders) to your development machine.

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

          hamzaelaziziH 1 Reply Last reply
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          • jsulmJ jsulm

            @hamzaelazizi Depends on how you created it. There are different ways. For example you can simply connect the SD card from your RaspberryPi to your development machine. Or you can copy the /usr content (at least lib and include subfolders) to your development machine.

            hamzaelaziziH Offline
            hamzaelaziziH Offline
            hamzaelazizi
            wrote on last edited by
            #6

            @jsulm do i need to install OpenCV On the host machine as well ?

            jsulmJ 1 Reply Last reply
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            • hamzaelaziziH hamzaelazizi

              @jsulm do i need to install OpenCV On the host machine as well ?

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

              @hamzaelazizi No, why should you if you want to cross compile? Host libraries have nothing to do with RaspberryPi.

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

              hamzaelaziziH 1 Reply Last reply
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              • jsulmJ jsulm

                @hamzaelazizi No, why should you if you want to cross compile? Host libraries have nothing to do with RaspberryPi.

                hamzaelaziziH Offline
                hamzaelaziziH Offline
                hamzaelazizi
                wrote on last edited by
                #8

                @jsulm then what path should i include in my .pro file ? i've created a small qt program on my host machine and i simply want to open an image and display it on the raspberry but i don't know what to include in my .pro file and when i compile it i get the error saying " :-1: error: cannot find -lm "

                jsulmJ 1 Reply Last reply
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                • hamzaelaziziH hamzaelazizi

                  @jsulm then what path should i include in my .pro file ? i've created a small qt program on my host machine and i simply want to open an image and display it on the raspberry but i don't know what to include in my .pro file and when i compile it i get the error saying " :-1: error: cannot find -lm "

                  jsulmJ Offline
                  jsulmJ Offline
                  jsulm
                  Lifetime Qt Champion
                  wrote on last edited by
                  #9

                  @hamzaelazizi said in Cross compile OpenCV to a RaspberryPI:

                  then what path should i include in my .pro file ?

                  The libraries you need I guess? Or what exactly are you asking?
                  In this case OpenCV libs you're using.
                  In QtCreator you should have a Kit for cross compilation where you set your cross compiled Qt and also path to your sysroot.
                  You need to understand the difference between compiling for host and cross compalation. If you compile for the host then libraries/headers installed on your host are used. But if you're doing cross compilation libraries and headers are taken from the sysroot.
                  You can find here information about QtCreator set-up for cross compilation: https://www.ics.com/blog/configuring-qt-creator-raspberry-pi

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

                  hamzaelaziziH 1 Reply Last reply
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                  • jsulmJ jsulm

                    @hamzaelazizi said in Cross compile OpenCV to a RaspberryPI:

                    then what path should i include in my .pro file ?

                    The libraries you need I guess? Or what exactly are you asking?
                    In this case OpenCV libs you're using.
                    In QtCreator you should have a Kit for cross compilation where you set your cross compiled Qt and also path to your sysroot.
                    You need to understand the difference between compiling for host and cross compalation. If you compile for the host then libraries/headers installed on your host are used. But if you're doing cross compilation libraries and headers are taken from the sysroot.
                    You can find here information about QtCreator set-up for cross compilation: https://www.ics.com/blog/configuring-qt-creator-raspberry-pi

                    hamzaelaziziH Offline
                    hamzaelaziziH Offline
                    hamzaelazizi
                    wrote on last edited by
                    #10

                    @jsulm i copied my folders "lib" and "include" where most of my OpenCV libraries are from the raspberry to the sysroot folder on my host machine but when i try to compile it keeps saying ":-1: error: cannot find -lm" i don't know why ?? i know it's an issue related to the math library but i don't know why it says this

                    jsulmJ 1 Reply Last reply
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                    • hamzaelaziziH hamzaelazizi

                      @jsulm i copied my folders "lib" and "include" where most of my OpenCV libraries are from the raspberry to the sysroot folder on my host machine but when i try to compile it keeps saying ":-1: error: cannot find -lm" i don't know why ?? i know it's an issue related to the math library but i don't know why it says this

                      jsulmJ Offline
                      jsulmJ Offline
                      jsulm
                      Lifetime Qt Champion
                      wrote on last edited by
                      #11

                      @hamzaelazizi How do you build?
                      Do you build in QtCreator?
                      How does your sysroot look like? Its structure should be: PATH_TO_SYSROOT/usr/* (* is lib and include)

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

                      hamzaelaziziH 1 Reply Last reply
                      0
                      • jsulmJ jsulm

                        @hamzaelazizi How do you build?
                        Do you build in QtCreator?
                        How does your sysroot look like? Its structure should be: PATH_TO_SYSROOT/usr/* (* is lib and include)

                        hamzaelaziziH Offline
                        hamzaelaziziH Offline
                        hamzaelazizi
                        wrote on last edited by
                        #12

                        @jsulm yes i build in Qt Creator
                        i didn't understand your second question but here is my sysroot path : "/home/rpi-qt/sysroot/* (* is lib and include and local)
                        local is the file i copied with the OpenCV libraries in
                        when i build and compile another project, it works and i can deploy the application on the Raspberry but when i try to do something with OpenCV it shows that error "cannot find -lm"

                        JonBJ 1 Reply Last reply
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                        • hamzaelaziziH hamzaelazizi

                          @jsulm yes i build in Qt Creator
                          i didn't understand your second question but here is my sysroot path : "/home/rpi-qt/sysroot/* (* is lib and include and local)
                          local is the file i copied with the OpenCV libraries in
                          when i build and compile another project, it works and i can deploy the application on the Raspberry but when i try to do something with OpenCV it shows that error "cannot find -lm"

                          JonBJ Online
                          JonBJ Online
                          JonB
                          wrote on last edited by JonB
                          #13

                          @hamzaelazizi said in Cross compile OpenCV to a RaspberryPI:

                          error "cannot find -lm"

                          It is looking for file libm.a. Probably because OpenCV needs the math library. On Ubuntu, for example, that is in /usr/lib/x86_64-linux-gnu/libm.a. I don't know where yours is/is supposed to be, in your cross-compilation situation. Linux command find / -name libm.a -print 2>/dev/null on whichever machine, and wherever you need to look down from where mine specifies /, should find it if present.

                          hamzaelaziziH 1 Reply Last reply
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                          • JonBJ JonB

                            @hamzaelazizi said in Cross compile OpenCV to a RaspberryPI:

                            error "cannot find -lm"

                            It is looking for file libm.a. Probably because OpenCV needs the math library. On Ubuntu, for example, that is in /usr/lib/x86_64-linux-gnu/libm.a. I don't know where yours is/is supposed to be, in your cross-compilation situation. Linux command find / -name libm.a -print 2>/dev/null on whichever machine, and wherever you need to look down from where mine specifies /, should find it if present.

                            hamzaelaziziH Offline
                            hamzaelaziziH Offline
                            hamzaelazizi
                            wrote on last edited by
                            #14

                            @JonB in case i was able to find its location, how can i tell Qt Creator to look for that library in that path ?

                            JonBJ 1 Reply Last reply
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                            • hamzaelaziziH hamzaelazizi

                              @JonB in case i was able to find its location, how can i tell Qt Creator to look for that library in that path ?

                              JonBJ Online
                              JonBJ Online
                              JonB
                              wrote on last edited by
                              #15

                              @hamzaelazizi
                              I have updated my post to give you a Linux find command to help you locate it.
                              Let's see where, if anywhere, it tells you it finds it before we know how to proceed.
                              I don't do cross-compilation so I don't know where you need to look or what to do about it when you find it, you may need @jsulm's help when you have told us where it is....

                              hamzaelaziziH 2 Replies Last reply
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                              • JonBJ JonB

                                @hamzaelazizi
                                I have updated my post to give you a Linux find command to help you locate it.
                                Let's see where, if anywhere, it tells you it finds it before we know how to proceed.
                                I don't do cross-compilation so I don't know where you need to look or what to do about it when you find it, you may need @jsulm's help when you have told us where it is....

                                hamzaelaziziH Offline
                                hamzaelaziziH Offline
                                hamzaelazizi
                                wrote on last edited by
                                #16

                                @JonB it gave me all these locations:

                                /home/rnsaoberon/rpi-qt/tools/cross-pi-gcc-8.3.0-2/arm-linux-gnueabihf/libc/usr/lib/libm.a
                                /home/rnsaoberon/rpi-qt/sysroot/lib/arm-linux-gnueabihf/libm.a
                                /home/rnsaoberon/rpi-qt/sysroot/usr/lib/arm-linux-gnueabihf/libm.a
                                /usr/arm-linux-gnueabi/libhf/libm.a
                                /usr/lib/x86_64-linux-gnu/libm.a
                                /usr/arm-linux-gnueabihf/lib/libm.a

                                i used the one with the Bold writing

                                1 Reply Last reply
                                0
                                • JonBJ JonB

                                  @hamzaelazizi
                                  I have updated my post to give you a Linux find command to help you locate it.
                                  Let's see where, if anywhere, it tells you it finds it before we know how to proceed.
                                  I don't do cross-compilation so I don't know where you need to look or what to do about it when you find it, you may need @jsulm's help when you have told us where it is....

                                  hamzaelaziziH Offline
                                  hamzaelaziziH Offline
                                  hamzaelazizi
                                  wrote on last edited by
                                  #17

                                  @JonB after i included the one i told you about i started having other errors :

                                  undefined reference to cv::imshow
                                  undefined reference to cv::imread undefined reference to cv::wait
                                  undefined reference to `cv::Mat

                                  JonBJ 1 Reply Last reply
                                  0
                                  • hamzaelaziziH hamzaelazizi

                                    @JonB after i included the one i told you about i started having other errors :

                                    undefined reference to cv::imshow
                                    undefined reference to cv::imread undefined reference to cv::wait
                                    undefined reference to `cv::Mat

                                    JonBJ Online
                                    JonBJ Online
                                    JonB
                                    wrote on last edited by
                                    #18

                                    @hamzaelazizi
                                    As I said, since I know nothing about cross-compilation or RPi you will have to await a comment from e.g. @jsulm as to what you are supposed to do....

                                    hamzaelaziziH 1 Reply Last reply
                                    0
                                    • JonBJ JonB

                                      @hamzaelazizi
                                      As I said, since I know nothing about cross-compilation or RPi you will have to await a comment from e.g. @jsulm as to what you are supposed to do....

                                      hamzaelaziziH Offline
                                      hamzaelaziziH Offline
                                      hamzaelazizi
                                      wrote on last edited by
                                      #19

                                      @JonB Okey i'll be waiting for him to reply back, hopefully he does

                                      jsulmJ 1 Reply Last reply
                                      0
                                      • hamzaelaziziH hamzaelazizi

                                        @JonB Okey i'll be waiting for him to reply back, hopefully he does

                                        jsulmJ Offline
                                        jsulmJ Offline
                                        jsulm
                                        Lifetime Qt Champion
                                        wrote on last edited by
                                        #20

                                        @hamzaelazizi Try this (add it to your pro file):

                                        LIBS += -L/usr/lib/arm-linux-gnueabihf -lm
                                        

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

                                        hamzaelaziziH 1 Reply Last reply
                                        2
                                        • jsulmJ jsulm

                                          @hamzaelazizi Try this (add it to your pro file):

                                          LIBS += -L/usr/lib/arm-linux-gnueabihf -lm
                                          
                                          hamzaelaziziH Offline
                                          hamzaelaziziH Offline
                                          hamzaelazizi
                                          wrote on last edited by
                                          #21

                                          @jsulm yes i changed the path to the one i have and it worked but it then started showing these different errors :

                                          undefined reference to cv::imshow
                                          undefined reference to cv::imread
                                          undefined reference to cv::wait
                                          undefined reference to cv::Mat

                                          1 Reply Last reply
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