OpenCV

OpenCV 2.3

The buildroot openCV package is not available yet in the buildroot version used by ARMadeus, however I will explain a little workaround to cross-compile this graphical library and use it on your ARMadeus plateform. I was inspired by the Opencv 2.1 section downwards.

This section has been written using an APF51 with the git-trunk ARMadeus version.

Buildroot configuration

• Install lib4vl

In your armadeus directory:

$ make menuconfig

Package Selection for the target  --->
  Hardware handling  --->
    [*] libv4l
      [*]   v4l2-ctl

• Take a look in...

Package Selection for the target  --->
  Libraries  --->
    Graphics  --->

... if the interesting format (jpg, png etc ...) for your application is checked.

Compiling and installing OpenCV-2.3.1

• Prepare the directories

$ mkdir OpenCV-2.3.1
$ cd OpenCV-2.3.1
$ mkdir build
$ mkdir src

• Get the source

$ cd src
$ wget http://sourceforge.net/projects/opencvlibrary/files/opencv-unix/2.3.1/OpenCV-2.3.1a.tar.bz2
$ tar xvjf OpenCV-2.3.1a.tar.bz2
$ cd ../

• Patch the source

This (dirty?) patch fix a compatibility problem with the long double type on ARM plateforme (fabsl not available).

OpenCV-2.3.1.patch

$ patch -p0 < OpenCV-2.3.1.patch

• Build Makefile from CMake

$ cd build
$ cmake -DCMAKE_BUILD_TYPE=RELEASE -DCMAKE_TOOLCHAIN_FILE:PATH=your_armadeus_directory/buildroot/output/toolchainfile.cmake -DCMAKE_INSTALL_PREFIX=your_armadeus_directory/buildroot/output/staging/usr/ -DCMAKE_BUILD_TYPE=RELEASE ../src/OpenCV-2.3.1/

Check if no error and the install path. You can configure your OpenCV compilation with...

$ cmake-gui

• Build OpenCV-2.3.1

$ make && make install

• Copy the libraries into your rootfs filesystem.

In your armadeus directory:

$ cp buildroot/output/staging/usr/lib/libopencv_* buildroot/output/target/usr/lib/

Test & example

This test was made with a Logitech QuickCam Communicate STX.

Configure your Linux Kernel

In your armadeus directory:

$ make linux-menuconfig

Check if the V4L driver is correctly checked:

Device Drivers  --->
  <M> Multimedia support  --->
     <M>   Video For Linux

And configure your driver, in our case for the Logitech QuickCam Communicate STX:

Device Drivers  --->
  <M> Multimedia support  --->
     [*]   Video capture adapters  --->
       [*]   V4L USB devices  --->
         <M>   GSPCA based webcams  --->
           <M>   ZC3XX USB Camera Driver

Reflash kernel and rootfs.

Build your application

In your armadeus directory

$ cd buildroot/output/build
$ mkdir opencv_example
$ cd opencv_example

In this directory, copy these files:

Makefile

opencv_example

$ make

Run the application test

On your APF board

# modprobe videodev
# modprobe gspca_zc3xx

Where gspca_zc3xx corresponding to my logitech webcam.

Then run the opencv_example application et check the picture test.jpg.

OpenCV 2.1

Page under construction... Informations on this page are not guaranteed !!

Forewords

This section explains how to (cross-)compile OpenCV 2.1.0 or later for your APF-board.

Pre-requisite

The CMake infrastructure has been integrated in Buildroot since the BR release 2011.02.

The CMake infrastructure is available in armadeus SDK since the armadeus-4.1 release (since it is based on BR release 2011.05).

Note: Using elder armadeus SDK requires having CMake 2.6 or later installed on the host system.

Build OpenCV

Note: The tutorial hereafter (patch and OpenCV configuration) is for the OpenCV 2.1.0 release. This may changes in newer OpenCV releases. Updates are welcome ;-)

1. Setup the CMake toolchain file:
   1. Using armadeus-4.1 SDK or later (or git view): this file is generated by buildroot and is located in armadeus-4.1/buildroot/output/toolchainfile.cmake.
   2. Using armadeus-4.0 SDK or former: the toolchainfile.cmake must be manually edited.
2. Create source and build directories

   mkdir -pv opencv-on-armadeus/{src,build}

3. Grab the OpenCV source archive.

   cd opencv-on-armadeus/src && wget http://sourceforge.net/projects/opencvlibrary/files/opencv-unix/2.1/OpenCV-2.1.0.tar.bz2 && tar xvvjf OpenCV-2.1.0.tar.bz2

4. Here, you'll have to apply this patch to avoid compilation failed:

   patch -p0 < OpenCV-2.1.0.patch

5. Run CMake (generate Makefiles)

   1. cd ~/opencv-on-armadeus/build && cmake -DCMAKE_TOOLCHAIN_FILE:PATH=/path/to/toolchainfile.cmake ../src/OpenCV-2.1.0

   2. It will certainly complain about unfound libraries and some other things, so adjust these things running:

      cmake-gui

6. Compile OpenCV libraries

   VERBOSE=1 make

Note: cmake-gui Click twice on Configure when you change something. When configuring exit without any error, click on Generate to generate Makefiles. If your configuration is too messy, reset it by deleting the cache (File/Delete Cache) or remove the CMakeCache.txt file in the build directory. Don't hesitate to do so if something (eg. paths) is wrong ;) To see the cmake-command that corresponds to the configuration you have just set in cmake-gui: Tools/Show my changes

Available features (for armadeus-4.0 release or former)

CMake looks for all required tool in the path specified in toolchainfile.cmake; therefore, some options, targets, libraries, ... are not available:

• Build:
  • Latex Doc  : Not available in Buildroot
  • New Python support  : Not available (require Python >=2.6, Buildroot provides Python 2.4)
  • Swing Python support : Not available (require Python >=2.6, Buildroot provides Python 2.4)
  • Octave support  : Not available in Buildroot
• Python
  • Executable  : Not found (require Python >=2.6, Buildroot provides Python 2.4)
  • Include dirs.  : Found
  • Library  : Not found (require Python >=2.6, Buildroot provides Python 2.4)
• With
  • V4L  : Disable it (Buildroot provides it, but linker failed)
• OpenCV
  • 3rd party libs.  : You can enable it.

Note: You may need to enable some packages in your Armadeus configuration to get some libraries (libjpeg, libpng and libtiff) found by CMake.

Run OpenCV applications on your APF-board

1. In the build directory, you should find a bin and a lib sub-directories. Copy them (at least the lib directory) on your target.

2. export LD_LIBRARY_PATH=/path/to/the/OpenCVlibdir

3. Run your application. You can try cvtest (some tests may fail because of missing resources), it will take a while... a long while ;)

See also

• OpenCV install guide

Appendices

OpenCV-2.3.1.patch

Index: src/OpenCV-2.3.1/modules/flann/include/opencv2/flann/dist.h
===================================================================
--- src/OpenCV-2.3.1/modules/flann/include/opencv2/flann/dist.h	2011-09-12 20:42:27.000000000 +0200
+++ src/OpenCV-2.3.1/modules/flann/include/opencv2/flann/dist.h	2012-02-05 15:10:28.715982724 +0100
@@ -60,7 +60,7 @@
 inline double abs<double>(double x) { return fabs(x); }
 
 template<>
-inline long double abs<long double>(long double x) { return fabsl(x); }
+inline long double abs<long double>(long double x) { return fabs(x); }
 
 
 template<typename T>

OpenCV-2.1.0.patch

--- OpenCV-2.1.0/3rdparty/flann/constants.h.origin	2010-06-08 01:14:22.171416516 +0200
+++ OpenCV-2.1.0/3rdparty/flann/constants.h	2010-06-08 01:15:06.912417891 +0200
@@ -41,7 +41,7 @@ enum flann_algorithm_t {
 	KMEANS = 2,
 	COMPOSITE = 3,
 	SAVED = 254,
-	AUTOTUNED = 255,
+	AUTOTUNED = 255
 };
 
 enum flann_centers_init_t {
--- OpenCV-2.1.0/3rdparty/flann/flann.h.origin	2010-06-08 01:14:32.588443815 +0200
+++ OpenCV-2.1.0/3rdparty/flann/flann.h	2010-06-08 01:15:06.912417891 +0200
@@ -267,7 +267,7 @@ LIBSPEC int flann_compute_cluster_center
 
 
 #ifdef __cplusplus
-};
+}
 
 
 #include "flann.hpp"
--- OpenCV-2.1.0/3rdparty/include/flann/constants.h.origin	2010-06-08 01:14:54.503416676 +0200
+++ OpenCV-2.1.0/3rdparty/include/flann/constants.h	2010-06-08 01:15:06.912417891 +0200
@@ -41,7 +41,7 @@ enum flann_algorithm_t {
 	KMEANS = 2,
 	COMPOSITE = 3,
 	SAVED = 254,
-	AUTOTUNED = 255,
+	AUTOTUNED = 255
 };
 
 enum flann_centers_init_t {
--- OpenCV-2.1.0/3rdparty/include/flann/flann.h.origin	2010-06-08 01:14:44.672417690 +0200
+++ OpenCV-2.1.0/3rdparty/include/flann/flann.h	2010-06-08 01:15:06.912417891 +0200
@@ -267,7 +267,7 @@ LIBSPEC int flann_compute_cluster_center
 
 
 #ifdef __cplusplus
-};
+}
 
 
 #include "flann.hpp"

opencv_example

Makefile

CC=../../host/usr/bin/arm-unknown-linux-uclibcgnueabi-gcc
all:
        $(CC) -Wall -o opencv_example -L../../staging/usr/lib/ -I../../staging/usr/include/ -lopencv_highgui opencv_example.c
clean:
        rm -rf opencv_example

opencv_example.c

#include <stdio.h>
#include <time.h>
#include <opencv/cv.h>
#include <opencv/highgui.h>

int main(int argc, char *argv[])
{

    CvCapture* capture = cvCreateCameraCapture(CV_CAP_V4L2);
    IplImage *img;

    if(!capture) {
        printf("Can't get capture device\n");
        exit(EXIT_FAILURE);
    }

    /* Grab some picture because the first ones is very dark */
    while (clock() / CLOCKS_PER_SEC < 3)
        cvGrabFrame(capture);

    /* Get one picture and save it as test.jpg */
    img = cvRetrieveFrame(capture, 0);
    cvSaveImage("test.jpg", img, 0);

  cvReleaseImage(&img );
  cvReleaseCapture(&capture);

  return EXIT_SUCCESS;
}