PlotOpenCv C++ library

v1.2.0

Table of contents

• Overview
• Versions
• Library files
• plot class description
  • Class declaration
  • getVersion method
  • Class constructor
  • addPlot (1D) method
  • addPlot (2D) method
  • clean method
  • show method
• Build and connect to your project
• Example

Overview

PlotOpenCv C++ library provides the visualization of 2-dimensional line charts. This library is built upon the OpenCV, providing users with a convenient and efficient tool for visualizing data through line charts. With PlotOpenCv, users can create multiple line charts within a single window and tune various chart parameters, such as line width, color, and more. It utilizes C++17 standard. The library is licensed under the Apache 2.0 license.

Versions

Table 1 - Library versions.

Version	Release date	What’s new
1.0.0	08.09.2023	First version.
1.0.1	18.09.2023	- Update used container for plots.
1.0.2	16.04.2024	- Antialiased line drawing implemented. - Window size issue fixed. - Documentation updated.
1.0.3	17.05.2024	- Documentation updated.
1.1.0	19.07.2024	- CMake structure updated. - Files renamed.
1.2.0	23.07.2024	- Files structure changed to hide opencv headers. - Library interface changed.

Library files

The library is supplied only by source code. The user is given a set of files in the form of a CMake project (repository). The repository structure is shown below:

CMakeLists.txt -------------- Main CMake file of the library.
src ------------------------- Library source code folder.
    CMakeLists.txt ---------- CMake file of the library.
    PlotOpenCv.h ------------ Main library header file.
    PlotOpenCvVersion.h ----- Header file with library version.
    PlotOpenCvVersion.h.in -- File for CMake to generate version header.
    PlotOpenCv.cpp ---------- C++ implementation file.
    Impl -------------------- Folder with plot implementation.
        PlotOpenCvImpl.h ---- Plot implementation header file.
        PlotOpenCvImpl.cpp -- C++ implementation file.
test ------------------------ Folder for test application.
    CMakeLists.txt ---------- CMake file of test application.
    main.cpp ---------------- Source code of test application.

Plot class description

Class declaration

Plot class declared in PlotOpenCv.h file. Class declaration:

namespace cr
{
namespace utils
{

/**
 * @brief Plot color.
*/
class PlotColor
{
public:
    /// Class constructor
    PlotColor(int b, int g, int r) : b(b), g(g), r(r) {}
    /// Blue color 0-255.  
    int b{0};
    /// Green color 0-255.
    int g{0};
    /// Red color 0-255.
    int r{0};
};

/**
 * @brief Plot class.
 */
class Plot
{
public:

    /// Get string of current library version.
    static std::string getVersion();

    /// Class constructor.
    Plot(std::string name, int width = 1280, int height = 720, 
         PlotColor backgroundColor = PlotColor(255, 255, 255),
         PlotColor scaleLineColor = PlotColor(0, 128, 128));

    /// Class destructor.
    ~Plot();

    /// Render plots on window.
    template <typename T>
    void addPlot(std::vector<T>& points, int id, int start = 0, int end = 0,
                 PlotColor color = PlotColor(255, 255, 255), int thickness = 1);

    /// Method to render plots on window.
    template <typename T>
    void addPlot(std::vector<std::vector<T>>& points, int id, 
                 int start = 0, int end = 0,
                 PlotColor color = PlotColor(255, 255, 255), int thickness = 1);

    /// Method to clean window.
    void clean();

    /// Method to show window.
    void show();
};
}
}

getVersion method

The getVersion() method returns string of current version of PlotOpenCv. Method declaration:

static std::string getVersion();

Method can be used without PlotOpenCv class instance:

std::cout << "PlotOpenCv class version: " << PlotOpenCv::getVersion();

Console output:

PlotOpenCv class version: 1.2.0

Class constructor

The Plot class constructor requires basic parameters. Constructor declaration:

Plot(std::string name, int width = 1280, int height = 720, 
     PlotColor backgroundColor = PlotColor(255, 255, 255),
     PlotColor scaleLineColor = PlotColor(0, 128, 128));

Parameter	Value
name	OpenCV window name.
width	Window width, pixels.
height	Window height, pixels.
backgroundColor	Background color, BGR.
scaleLineColor	Scale line color, BGR.

Example of class initialization:

Plot graph("Test graph", 1280, 640, PlotColor(50, 50, 50));

addPlot (for 1D dataset) method

The addPlot(…) method serves the purpose of incorporating a new line chart into the existing window. It either introduces a new plot if the provided id is not yet present, or updates an existing plot associated with the given identifier. Method declaration:

void addPlot(std::vector<T> &points, int id, int start = 0, int end = 0,
            cv::Scalar color = cv::Scalar(255, 255, 255), int thickness = 1);

Parameter	Value
Points	One dimensional vector which includes vertical points. Vector format : {y1, y2, … }
id	Identifier for chart on a window. Provides user to update a chart or add new one.
start	Start index of plot from vector when user wants to plot a specific range from a dataset. Should be 0 for whole dataset.
end	End index of plot from vector when user wants to plot a specific range from a dataset. Should be 0 for whole dataset.
color	Color of chart line.
thickness	Thickness of chart line.

addPlot (for 2D dataset) method

The addPlot(…) method serves the purpose of incorporating a new line chart into the existing window. It either introduces a new plot if the provided id is not yet present, or updates an existing plot associated with the given identifier. Method declaration:

template <typename T>
void addPlot(std::vector<std::vector<T>>& points, int id, 
             int start = 0, int end = 0,
             PlotColor color = PlotColor(255, 255, 255), int thickness = 1);

Parameter	Value
Points	Two dimensional vector which includes vertical and horizontal points. Vector format:[{x1,y1}, {x2,y2}, … ]
id	Identifier for chart on a window. Provides user to update a chart or add new one.
start	Start index of plot from vector when user wants to plot a specific range from a dataset. Should be 0 for whole dataset.
end	End index of plot from vector when user wants to plot a specific range from a dataset. Should be 0 for whole dataset.
color	Color of chart line.
thickness	Thickness of chart line.

Table 2 - Supported data types.

Supported data types
unsigned char
char
unsigned int
unsigned short
short int
int
float
double

show method

The show() method is responsible for displaying a window containing all the plotted line charts. Method declaration:

void show();

clean method

The clean() method is responsible for cleaning a window containing all the plotted line charts. Method declaration:

void clean();

Build and connect to your project

Typical commands to build PlotOpenCv library:

cd PlotOpenCv
mkdir build
cd build
cmake ..
make

If you want connect PlotOpenCv library to your CMake project as source code you can make follow. For example, if your repository has structure:

CMakeLists.txt
src
    CMakeList.txt
    yourLib.h
    yourLib.cpp

Create folder 3rdparty in your repository and copy PlotOpenCv repository folder there. New structure of your repository:

CMakeLists.txt
src
    CMakeList.txt
    yourLib.h
    yourLib.cpp
3rdparty
    PlotOpenCv

Create CMakeLists.txt file in 3rdparty folder. CMakeLists.txt should contain:

cmake_minimum_required(VERSION 3.13)

################################################################################
## 3RD-PARTY
## dependencies for the project
################################################################################
project(3rdparty LANGUAGES CXX)

################################################################################
## SETTINGS
## basic 3rd-party settings before use
################################################################################
# To inherit the top-level architecture when the project is used as a submodule.
SET(PARENT ${PARENT}_YOUR_PROJECT_3RDPARTY)
# Disable self-overwriting of parameters inside included subdirectories.
SET(${PARENT}_SUBMODULE_CACHE_OVERWRITE OFF CACHE BOOL "" FORCE)

################################################################################
## CONFIGURATION
## 3rd-party submodules configuration
################################################################################
SET(${PARENT}_SUBMODULE_PLOT_OPENCV                     ON  CACHE BOOL "" FORCE)
if (${PARENT}_SUBMODULE_PLOT_OPENCV)
    SET(${PARENT}_PLOT_OPENCV                           ON  CACHE BOOL "" FORCE)
    SET(${PARENT}_PLOT_OPENCV_TEST                      OFF CACHE BOOL "" FORCE)
endif()

################################################################################
## INCLUDING SUBDIRECTORIES
## Adding subdirectories according to the 3rd-party configuration
################################################################################
if (${PARENT}_SUBMODULE_PLOT_OPENCV)
    add_subdirectory(PlotOpenCv)
endif()

File 3rdparty/CMakeLists.txt adds folder PlotOpenCv to your project and excludes test applications from compiling (by default test applications and example excluded from compiling if PlotOpenCv included as sub-repository).The new structure of your repository:

CMakeLists.txt
src
    CMakeList.txt
    yourLib.h
    yourLib.cpp
3rdparty
    CMakeLists.txt
    PlotOpenCv

Next you need include folder 3rdparty in main CMakeLists.txt file of your repository. Add string at the end of your main CMakeLists.txt:

add_subdirectory(3rdparty)

Next you have to include PlotOpenCv library in your src/CMakeLists.txt file:

target_link_libraries(${PROJECT_NAME} PlotOpenCv)

Done!

Example

The example demonstrates how to use PlotOpenCv library.

#include <vector>
#include <opencv2/opencv.hpp>
#include <opencv2/highgui.hpp>
#include "PlotOpenCv.h"

int main()
{    
	plot graph("Test graph", 1280, 720, PlotColor(0, 128, 128) PlotColor(50, 50, 50));

    std::vector<float> linePoints(9000);
    std::vector<std::vector<float>> linePoints2(5000, std::vector<float>(2));

    graph.addPlot(linePoints, 0, 0, 0, PlotColor(255,0,0), 5);
    graph.addPlot(linePoints2, 1, 0, 0, PlotColor(0,255,0), 2);

    graph.show();
    cv::waitKey(0);
    return 0;
}

Example charts shows what visual effects user should expect depending on input data: