First Samplle for OpenCV with ImGui

CMakeLists.txt

cmake_minimum_required( VERSION 3.6 )

set( CMAKE_CXX_STANDARD 11 )
set( CMAKE_CXX_STANDARD_REQUIRED ON )
set( CMAKE_CXX_EXTENSIONS OFF )

find_package( Git )
execute_process(
  COMMAND ${GIT_EXECUTABLE} clone "https://github.com/ocornut/imgui.git" -b v1.72b
  WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
)
set( IMGUI_DIR ${CMAKE_CURRENT_BINARY_DIR}/imgui )

set( imgui_files
  ${IMGUI_DIR}/imconfig.h
  ${IMGUI_DIR}/imgui.cpp
  ${IMGUI_DIR}/imgui.h
  ${IMGUI_DIR}/imgui_demo.cpp
  ${IMGUI_DIR}/imgui_draw.cpp
  ${IMGUI_DIR}/imgui_internal.h
  ${IMGUI_DIR}/imgui_widgets.cpp
  ${IMGUI_DIR}/imstb_rectpack.h
  ${IMGUI_DIR}/imstb_textedit.h
  ${IMGUI_DIR}/imstb_truetype.h
)

set( imgui_impl_files
  ${IMGUI_DIR}/examples/imgui_impl_glfw.h
  ${IMGUI_DIR}/examples/imgui_impl_glfw.cpp
  ${IMGUI_DIR}/examples/imgui_impl_opengl3.h
  ${IMGUI_DIR}/examples/imgui_impl_opengl3.cpp
)

set( gl3w
  ${IMGUI_DIR}/examples/libs/gl3w/GL/gl3w.c
)

project( sample )
add_executable( sample ${imgui_files} ${imgui_impl_files} ${gl3w} main.cpp )

set_property( DIRECTORY PROPERTY VS_STARTUP_PROJECT "sample" )

find_package( OpenCV REQUIRED )
find_package( OpenGL REQUIRED )

include( ExternalProject )
ExternalProject_Add(
  glfw PREFIX glfw
  GIT_REPOSITORY https://github.com/glfw/glfw.git
  GIT_TAG 3.3
  CMAKE_ARGS
    "-DCMAKE_INSTALL_PREFIX=<INSTALL_DIR>"
    "-DCMAKE_BUILD_TYPE=Release"
    "-DGLFW_BUILD_DOCS=OFF"
    "-DGLFW_BUILD_EXAMPLES=OFF"
    "-DGLFW_BUILD_TESTS=OFF"
)
ExternalProject_Get_Property( glfw INSTALL_DIR )
set( GLFW_DIR ${INSTALL_DIR} )
set( GLFW_INCLUDE_DIR ${GLFW_DIR}/include )
set( GLFW_LIBRARIES   ${GLFW_DIR}/lib/${CMAKE_STATIC_LIBRARY_PREFIX}glfw3${CMAKE_STATIC_LIBRARY_SUFFIX} )
add_dependencies( sample glfw )

if( OpenCV_FOUND AND OPENGL_FOUND )
  include_directories( ${IMGUI_DIR} )
  include_directories( ${IMGUI_DIR}/examples )
  include_directories( ${IMGUI_DIR}/examples/libs/gl3w )
  include_directories( ${OPENGL_INCLUDE_DIR} )
  include_directories( ${GLFW_INCLUDE_DIR} )

  target_link_libraries( sample ${OpenCV_LIBS} )
  target_link_libraries( sample ${OPENGL_LIBRARIES} )
  target_link_libraries( sample ${GLFW_LIBRARIES} )
endif()

main.cpp

#include <iostream>
#include <opencv2/opencv.hpp>

#include "imgui.h"
#include "imgui_impl_glfw.h"
#include "imgui_impl_opengl3.h"
#include <GL/gl3w.h>
#include <GLFW/glfw3.h>

int main( int argc, char* argv[] )
{
    cv::Mat image = cv::imread( "../lena.jpg", cv::IMREAD_COLOR );
    if( image.empty() ){
        return -1;
    }
    cv::cvtColor( image, image, cv::COLOR_BGR2RGBA );

    if( !glfwInit() ){
        return -1;
    }

    GLFWwindow* window = glfwCreateWindow( 800, 600, "glfw window", nullptr, nullptr );
    glfwSetWindowCloseCallback( window, []( GLFWwindow* window ){ glfwSetWindowShouldClose( window, GL_FALSE ); } );
    glfwMakeContextCurrent( window );
    glfwSwapInterval( 1 );
    gl3wInit();

    IMGUI_CHECKVERSION();
    ImGui::CreateContext();

    ImGui_ImplGlfw_InitForOpenGL( window, true );
    ImGui_ImplOpenGL3_Init( "#version 330" );

    bool is_show = true;
    while( is_show ){
        glfwPollEvents();
        glClearColor( 0.0f, 0.0f, 0.0f, 1.0f );
        glClear( GL_COLOR_BUFFER_BIT );

        ImGui_ImplOpenGL3_NewFrame();
        ImGui_ImplGlfw_NewFrame();
        ImGui::NewFrame();

        ImGui::Begin( "imgui image", &is_show );
        GLuint texture;
        glGenTextures( 1, &texture );
        glBindTexture( GL_TEXTURE_2D, texture );
        glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
        glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
        glPixelStorei( GL_UNPACK_ROW_LENGTH, 0 );
        glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, image.cols, image.rows, 0, GL_RGBA, GL_UNSIGNED_BYTE, image.data );
        ImGui::Image( reinterpret_cast<void*>( static_cast<intptr_t>( texture ) ), ImVec2( image.cols, image.rows ) );
        ImGui::End();

        ImGui::Render();
        ImGui_ImplOpenGL3_RenderDrawData( ImGui::GetDrawData() );

        glfwSwapBuffers( window );
    }

    ImGui_ImplGlfw_Shutdown();
    ImGui_ImplOpenGL3_Shutdown();
    ImGui::DestroyContext();
    glfwTerminate();

    return 0;
}