Mostra la font per a OpenCV a Ubuntu 18.04

__TOC__
=Instal·lació=
Seguim el següent tutorial:
*https://linuxize.com/post/how-to-install-opencv-on-ubuntu-18-04/

Building the OpenCV library from source is the recommended way of installing OpenCV. It will be optimized for your particular system and you will have complete control over the build options.

1. Install the required dependencies:
<pre>
sudo apt install build-essential cmake git pkg-config libgtk-3-dev \
    libavcodec-dev libavformat-dev libswscale-dev libv4l-dev \
    libxvidcore-dev libx264-dev libjpeg-dev libpng-dev libtiff-dev \
    gfortran openexr libatlas-base-dev python3-dev python3-numpy \
    libtbb2 libtbb-dev libdc1394-22-dev
</pre>
2. Clone the OpenCV's and OpenCV contrib repositories:
<pre>
mkdir ~/opencv_build && cd ~/opencv_build
git clone https://github.com/opencv/opencv.git
git clone https://github.com/opencv/opencv_contrib.git
</pre>
3. Once the download is complete, create a temporary build directory, and switch to it:
<pre>
cd ~/opencv_build/opencv
mkdir build && cd build
</pre>
Set up the OpenCV build with CMake:
<pre>
cmake -D CMAKE_BUILD_TYPE=RELEASE \
    -D CMAKE_INSTALL_PREFIX=/usr/local \
    -D INSTALL_C_EXAMPLES=ON \
    -D INSTALL_PYTHON_EXAMPLES=ON \
    -D OPENCV_GENERATE_PKGCONFIG=ON \
    -D OPENCV_EXTRA_MODULES_PATH=~/opencv_build/opencv_contrib/modules \
    -D BUILD_EXAMPLES=ON ..
</pre>
<pre>
...
--   OpenCV modules:
--     To be built:                 aruco bgsegm bioinspired calib3d ccalib core datasets dnn dnn_objdetect dnn_superres dpm face features2d flann freetype fuzzy gapi hfs highgui img_hash imgcodecs imgproc line_descriptor ml objdetect optflow phase_unwrapping photo plot python3 quality rapid reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking ts video videoio videostab xfeatures2d ximgproc xobjdetect xphoto
--     Disabled:                    world
--     Disabled by dependency:      -
--     Unavailable:                 cnn_3dobj cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev cvv hdf java js matlab ovis python2 sfm viz
--     Applications:                tests perf_tests examples apps
--     Documentation:               NO
--     Non-free algorithms:         NO
-- 
--   GUI: 
--     GTK+:                        YES (ver 3.22.30)
--       GThread :                  YES (ver 2.56.4)
--       GtkGlExt:                  NO
--     VTK support:                 NO
-- 
--   Media I/O: 
--     ZLib:                        /usr/lib/x86_64-linux-gnu/libz.so (ver 1.2.11)
--     JPEG:                        /usr/lib/x86_64-linux-gnu/libjpeg.so (ver 80)
--     WEBP:                        build (ver encoder: 0x020e)
--     PNG:                         /usr/lib/x86_64-linux-gnu/libpng.so (ver 1.6.34)
--     TIFF:                        /usr/lib/x86_64-linux-gnu/libtiff.so (ver 42 / 4.0.9)
--     JPEG 2000:                   build (ver 1.900.1)
--     OpenEXR:                     build (ver 2.3.0)
--     HDR:                         YES
--     SUNRASTER:                   YES
--     PXM:                         YES
--     PFM:                         YES
-- 
--   Video I/O:
--     DC1394:                      YES (2.2.5)
--     FFMPEG:                      YES
--       avcodec:                   YES (57.107.100)
--       avformat:                  YES (57.83.100)
--       avutil:                    YES (55.78.100)
--       swscale:                   YES (4.8.100)
--       avresample:                NO
--     GStreamer:                   NO
--     v4l/v4l2:                    YES (linux/videodev2.h)
-- 
--   Parallel framework:            pthreads
-- 
--   Trace:                         YES (with Intel ITT)
-- 
--   Other third-party libraries:
--     Intel IPP:                   2019.0.0 Gold [2019.0.0]
--            at:                   /home/joan/opencv_build/opencv/build/3rdparty/ippicv/ippicv_lnx/icv
--     Intel IPP IW:                sources (2019.0.0)
--               at:                /home/joan/opencv_build/opencv/build/3rdparty/ippicv/ippicv_lnx/iw
--     Lapack:                      NO
--     Eigen:                       NO
--     Custom HAL:                  NO
--     Protobuf:                    build (3.5.1)
-- 
--   OpenCL:                        YES (no extra features)
--     Include path:                /home/joan/opencv_build/opencv/3rdparty/include/opencl/1.2
--     Link libraries:              Dynamic load
-- 
--   Python 3:
--     Interpreter:                 /usr/bin/python3 (ver 3.6.9)
--     Libraries:                   /usr/lib/x86_64-linux-gnu/libpython3.6m.so (ver 3.6.9)
--     numpy:                       /usr/local/lib/python3.6/dist-packages/numpy/core/include (ver 1.17.4)
--     install path:                lib/python3.6/dist-packages/cv2/python-3.6
-- 
--   Python (for build):            /usr/bin/python2.7
-- 
--   Java:                          
--     ant:                         NO
--     JNI:                         NO
--     Java wrappers:               NO
--     Java tests:                  NO
-- 
--   Install to:                    /usr/local
-- -----------------------------------------------------------------
-- 
-- Configuring done
-- Generating done
-- Build files have been written to: /home/joan/opencv_build/opencv/buil
</pre>
4. Start the compilation process:

<pre>
$ make -j8

...
[100%] Built target opencv_python3
</pre>

5. Install OpenCV with:
<pre>
sudo make install
</pre>
6. To verify whether OpenCV has been installed successfully, type the following command and you should see the OpenCV version:
<pre>
pkg-config --modversion opencv4
4.2.0

$ python3 -c "import cv2; print(cv2.__version__)"
4.2.0-dev
</pre>
=Primeres proves amb python3=
*https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_core/py_basic_ops/py_basic_ops.html#basic-ops

<pre>
$ python3
Python 3.6.9 (default, Nov  7 2019, 10:44:02) 
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import cv2
>>> import numpy as np
>>> img = cv2.imread('1151.jpg')
>>> px = img[100,100]

>>> print (px)
[255 255 255]
>>> blue = img[100,100,0]
>>> print (blue)
255
>>> print (img.shape)
(911, 670, 3)
>>> print (img.size)
1831110
>>> print (img.dtype)
uint8
</pre>
=Primeres proves amb C++=
Però a '''/usr/include''' encara no hi ha cap carpeta relacionada amb '''opencv'''.
<pre>
$ sudo apt-get install libopencv-dev
</pre>
Ara sí:
<pre>
$ ls /usr/include
...
opencv
opencv2
...
</pre>
Però també: (potser això ja ho tenia i no calia instal·lar la llibreria...)
<pre>
$ ls /usr/local/include
opencv4
</pre>

<pre>
$ pkg-config --cflags opencv
-I/usr/include/opencv

$ pkg-config --cflags opencv4
-I/usr/local/include/opencv4/opencv -I/usr/local/include/opencv4


$ pkg-config --modversion opencv
3.2.0

$ pkg-config --modversion opencv4
4.2.0
</pre>
<pre>
$ pkg-config --libs opencv
-lopencv_shape -lopencv_stitching -lopencv_superres -lopencv_videostab -lopencv_aruco -lopencv_bgsegm -lopencv_bioinspired -lopencv_ccalib -lopencv_datasets -lopencv_dpm -lopencv_face -lopencv_freetype -lopencv_fuzzy -lopencv_hdf -lopencv_line_descriptor -lopencv_optflow -lopencv_video -lopencv_plot -lopencv_reg -lopencv_saliency -lopencv_stereo -lopencv_structured_light -lopencv_phase_unwrapping -lopencv_rgbd -lopencv_viz -lopencv_surface_matching -lopencv_text -lopencv_ximgproc -lopencv_calib3d -lopencv_features2d -lopencv_flann -lopencv_xobjdetect -lopencv_objdetect -lopencv_ml -lopencv_xphoto -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -lopencv_photo -lopencv_imgproc -lopencv_core

$ pkg-config --libs opencv4
-L/usr/local/lib -lopencv_gapi -lopencv_stitching -lopencv_aruco -lopencv_bgsegm -lopencv_bioinspired -lopencv_ccalib -lopencv_dnn_objdetect -lopencv_dnn_superres -lopencv_dpm -lopencv_highgui -lopencv_face -lopencv_freetype -lopencv_fuzzy -lopencv_hfs -lopencv_img_hash -lopencv_line_descriptor -lopencv_quality -lopencv_rapid -lopencv_reg -lopencv_rgbd -lopencv_saliency -lopencv_stereo -lopencv_structured_light -lopencv_phase_unwrapping -lopencv_superres -lopencv_optflow -lopencv_surface_matching -lopencv_tracking -lopencv_datasets -lopencv_text -lopencv_dnn -lopencv_plot -lopencv_videostab -lopencv_videoio -lopencv_xfeatures2d -lopencv_shape -lopencv_ml -lopencv_ximgproc -lopencv_video -lopencv_xobjdetect -lopencv_objdetect -lopencv_calib3d -lopencv_imgcodecs -lopencv_features2d -lopencv_flann -lopencv_xphoto -lopencv_photo -lopencv_imgproc -lopencv_core
</pre>
I faig el primer exemple que obtinc de:
*https://pydeeplearning.com/opencv/install-opencv-with-c-on-ubuntu-18-04/

script '''img-display.cpp''':
<pre>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>

using namespace cv;
using namespace std;

int main( int argc, char** argv )
{
    if( argc != 2)
    {
     cout <<" Usage: display_image ImageToLoadAndDisplay" << endl;
     return -1;
    }

    Mat image;
    image = imread(argv[1], CV_LOAD_IMAGE_COLOR);   // Read the file

    if(! image.data )                              // Check for invalid input
    {
        cout << "Could not open or find the image" << std::endl ;
        return -1;
    }

    namedWindow( "Display window", WINDOW_AUTOSIZE );// Create a window for display.
    imshow( "Display window", image );                // Show our image inside it.

    waitKey(0);             // Wait for a keystroke in the window
    return 0;
}
</pre>
<pre>
$ g++ img-display.cpp -o img-display `pkg-config --cflags --libs opencv`

$ ./img-display 1151.jpg
</pre>


{{Autor}}, gener 2020