Update OpenCV 4 source installation Ubuntu blog.

Install-OpenCV-4-on-Ubuntu-from-source/CMakeLists.txt

@@ -0,0 +1,15 @@
+cmake_minimum_required(VERSION 2.8.12)
+
+PROJECT(Project)
+
+SET(OpenCV_DIR /path/to/opencv/config)
+find_package(OpenCV REQUIRED)
+
+include_directories(${OpenCV_INCLUDE_DIRS})
+
+MACRO(add_example name)
+  ADD_EXECUTABLE(${name} ${name}.cpp)
+  TARGET_LINK_LIBRARIES(${name} ${OpenCV_LIBS})
+ENDMACRO()
+
+add_example(sampleCode)

Install-OpenCV-4-on-Ubuntu-from-source/README.md

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+# Code for Install OpenCV 4 on Ubuntu from source
+
+This repository contains the sample code for [Install OpenCV 4 on Ubuntu from source](https://learnopencv.com/install-opencv-4-on-ubuntu-18-04/)
+
+## Run Code:
+
+### C++
+```
+mkdir build
+cd build
+cmake ..
+cmake --build . --config Release
+cd ..
+./build/sampleCode
+```
+
+### Python
+```
+python sampleCode.py 
+```
+
+# AI Courses by OpenCV
+
+Want to become an expert in AI? [AI Courses by OpenCV](https://opencv.org/courses/) is a great place to start. 
+
+<a href="https://opencv.org/courses/">
+<p align="center"> 
+<img src="https://www.learnopencv.com/wp-content/uploads/2020/04/AI-Courses-By-OpenCV-Github.png">
+</p>
+</a>

Install-OpenCV-4-on-Ubuntu-from-source/sampleCode.cpp

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+#include <opencv2/opencv.hpp>
+#include <iostream>
+
+using namespace std;
+using namespace cv;
+
+int main(int argc, char **argv)
+{
+    // Print OpenCV Version
+    cout << CV_VERSION << endl;
+
+    // Read image
+    Mat image = imread("boy.jpg", 1);
+
+    // Convert image to grayscale
+    cvtColor(image, image, COLOR_BGR2GRAY);
+
+    // Display image
+    imshow("Display", image);
+    waitKey(0);
+
+    // Save grayscale image
+    imwrite("boyGray.jpg",image);
+
+    return 0;
+}

Install-OpenCV-4-on-Ubuntu-from-source/sampleCode.py

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+import cv2 as cv
+
+# Print OpenCV Version
+print(cv.__version__)
+
+# Read image
+image = cv.imread("boy.jpg", 1)
+
+# Convert image to grayscale
+image = cv.cvtColor(image, cv.COLOR_BGR2GRAY)
+
+# Display image
+cv.imshow("Display", image)
+cv.waitKey(0)
+
+# Save grayscale image
+cv.imwrite("boyGray.jpg",image)

README.md

@@ -100,7 +100,7 @@ Want to become an expert in AI? [AI Courses by OpenCV](https://opencv.org/course
 |[Install OpenCV 4 on Windows (C++ and Python)](https://www.learnopencv.com/install-opencv-4-on-windows/) | [Code](https://github.com/spmallick/learnopencv/tree/master/InstallScripts/Windows-4) |
 |[Hand Keypoint Detection using Deep Learning and OpenCV](https://www.learnopencv.com/hand-keypoint-detection-using-deep-learning-and-opencv/) | [Code](https://github.com/spmallick/learnopencv/tree/master/HandPose)|
 |[Deep learning based Object Detection and Instance Segmentation using Mask R-CNN in OpenCV (Python / C++)](https://www.learnopencv.com/deep-learning-based-object-detection-and-instance-segmentation-using-mask-r-cnn-in-opencv-python-c/) | [Code](https://github.com/spmallick/learnopencv/tree/master/Mask-RCNN) |
-|[Install OpenCV 4 on Ubuntu 18.04 (C++ and Python)](https://www.learnopencv.com/install-opencv-4-on-ubuntu-18-04/) | [Code](https://github.com/spmallick/learnopencv/blob/master/InstallScripts/installOpenCV-4-on-Ubuntu-18-04.sh) |
+|[Install OpenCV 4 on Ubuntu (C++ and Python)](https://www.learnopencv.com/install-opencv-4-on-ubuntu-18-04/) | [Code](https://github.com/spmallick/learnopencv/blob/master/Install-OpenCV-4-on-Ubuntu-from-source) |
 |[Install OpenCV 4 on Ubuntu 16.04 (C++ and Python)](https://www.learnopencv.com/install-opencv-4-on-ubuntu-16-04/) | [Code](https://github.com/spmallick/learnopencv/blob/master/InstallScripts/installOpenCV-4-on-Ubuntu-16-04.sh) |
 |[Multi-Person Pose Estimation in OpenCV using OpenPose](https://www.learnopencv.com/multi-person-pose-estimation-in-opencv-using-openpose/) | [Code](https://github.com/spmallick/learnopencv/tree/master/OpenPose-Multi-Person) |
 |[Heatmap for Logo Detection using OpenCV (Python)](https://www.learnopencv.com/heatmap-for-logo-detection-using-opencv-python/) | [Code](https://github.com/spmallick/learnopencv/tree/master/heatmap)|