imgui开发笔记＜4＞、image-slider online

　在线滑条二值化。

//
// Created by sry on 2021/6/30.
//

#include"imgui.h"
#include "imgui_impl_glfw.h"
#include "imgui_impl_opengl3.h"
#include <stdio.h>
// Initialize with gl3wInit()
#include<GL/gl3w.h>
// Include glfw3.h after our OpenGL definitions
#include <GLFW/glfw3.h>
#include<iostream>

#include<opencv2/opencv.hpp>

GLuint textureID;
cv::VideoCapture vcap;
bool FlagWetCamera = false;
bool FlagOpenCamera = false;

void imageProcess(const cv::Mat& image)
{
    //设置长宽
    int width = image.cols;
    int height = image.rows;
    int channel = image.channels();

    //获取图像指针
    int pixellength = width * height * channel;
    GLubyte* pixels = new GLubyte[pixellength];
    memcpy(pixels, image.data, pixellength * sizeof(char));

    // 使用GL指令生成贴图，获取贴图ID
    glGenTextures(1, &textureID);
    glBindTexture(GL_TEXTURE_2D, textureID);
    //必须一个RGB  一个BGR（opencv的mat类的颜色通道是BGR） 否则会出现颜色偏差
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, pixels);
    //纹理放大缩小使用线性插值
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glBindTexture(GL_TEXTURE_2D, 0);
    free(pixels);

}

static void glfw_error_callback(int error, const char* description)
{

    fprintf(stderr, "Glfw Error %d: %s\n", error, description);
}

int main()
{
    glfwSetErrorCallback(glfw_error_callback);
    if (!glfwInit())
    {
        return 1;
    }
    const char* glsl_version = "#version 130"; //
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
    // 创建窗口
    GLFWwindow* window = glfwCreateWindow(1280, 720, "Dear ImGui GLFW+OpenGL3 example", NULL, NULL);
    if (window == NULL)
    {
        return 1;
    }
    glfwMakeContextCurrent(window);
    glfwSwapInterval(1); //  开启垂直同步

    if (gl3wInit() != 0)
    {
        fprintf(stderr, "Failed to initialize OpenGL loader!\n");
        return -1;
    }
    // 启动 ImGui 上下文
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO();
    (void)io;

    io.WantSaveIniSettings = true;
    io.IniFilename = "sry.ini";

    // 主题
    ImGui::StyleColorsDark();
    // 启动 平台、渲染 后端
    ImGui_ImplGlfw_InitForOpenGL(window, true);
    ImGui_ImplOpenGL3_Init(glsl_version);
    ImVec4 clear_color = ImVec4(0.f, 0.75f, 0.f, 0.30f);

    // 基于OpenCV加载图片
    cv::Mat image = cv::imread("d:/lena.jpg", 0);
    /*cv::Mat imageBW = cv::Mat::zeros(image.size(), CV_8UC1);
    cv::threshold(image, imageBW, 255, 255, cv::THRESH_BINARY);
    cv::imshow("bw", imageBW);
    cv::waitKey(0);*/
    cv::Mat imageBW = cv::Mat::zeros(image.size(), CV_8UC1);
    static float t = 100.f;
    cv::threshold(image, imageBW, t, 255, cv::THRESH_BINARY);
    cv::Mat imageBW_ = cv::Mat::zeros(image.size(), CV_8UC3);
    cv::cvtColor(imageBW, imageBW_, cv::COLOR_GRAY2BGRA);
    while (!glfwWindowShouldClose(window))
    {
        // 处理所有待办时间
        glfwPollEvents();
        // 启动imgui frame,刷新帧
        ImGui_ImplOpenGL3_NewFrame();
        ImGui_ImplGlfw_NewFrame();
        ImGui::NewFrame();

        // 显示图像
        {
            // //设置窗口的padding为0是图片控件充满窗口
            ImGui::PushStyleVar(ImGuiStyleVar_FramePadding, ImVec2(0, 0));
            //设置窗口的边框大小为0
            ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0);
            // 改变窗口的背景颜色
            ImGui::PushStyleColor(ImGuiCol_WindowBg, ImVec4(0, 0, 100, 0.3));

            ImGui::Begin("camera", NULL, ImGuiWindowFlags_NoBringToFrontOnFocus);

            if (ImGui::SliderFloat("slider float", &t, 0.0f, 255.0f, "ratio = %.3f"))
            {
                cv::threshold(image, imageBW, t, 255, cv::THRESH_BINARY);
                cv::cvtColor(imageBW, imageBW_, cv::COLOR_GRAY2BGRA);
            }


            imageProcess(imageBW_);

            ImTextureID image_id = (GLuint*)textureID;
            ImGui::Image(image_id, ImGui::GetContentRegionAvail());
            //ImGui::Image(image_id, ImGui::GetContentRegionAvail(), ImVec2(0.0, 0.0), ImVec2(1.0, 1.0), ImVec4(0, 0, 255, 1), ImVec4(0, 255, 0, 1));

            ImGui::End();

            ImGui::PopStyleVar(2);
            ImGui::PopStyleColor(1);

        }


        // 渲染子窗口
        ImGui::Render();
        // 主窗口背景颜色
        gl3wClearColor(clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w);
        glClear(GL_COLOR_BUFFER_BIT);

        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
        glfwSwapBuffers(window);
    }

    // Release

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

    glfwDestroyWindow(window);
    glfwTerminate();
    return 1;
}