使用 openCV 和 openGL 显示来自网络摄像头的图像 [英] Display a image from the Webcam using openCV and openGL

问题描述

我正在使用 openCV 从网络摄像头捕捉图片.然后应该将框架转换为 openGL 纹理并显示在屏幕上.我得到了以下代码，但窗口仍然是黑色的.我对 openGL 很陌生，不知道为什么它不起作用.

I'm capturing a picture from a webcam with openCV. Then the frame should be transformed into an openGL texture and be shown on the screen. I got the following code but the window remains black. I'm very new to openGL and have no more ideas why it doesn't work.

int main ()
{
    int w = 800,h=600;

    glfwInit();

    //configure glfw 
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);


    GLFWwindow* window = glfwCreateWindow(w, h, "OpenGL", NULL, nullptr); // windowed
    glfwMakeContextCurrent(window);

    glewExperimental = GL_TRUE;
    glewInit();

    initializeCapturing();

    //init GL
    glViewport(0, 0, w, h); // use a screen size of WIDTH x HEIGHT
    glEnable(GL_TEXTURE_2D);     // Enable 2D texturing

    glMatrixMode(GL_PROJECTION);     // Make a simple 2D projection on the entire window
    glLoadIdentity();
    glOrtho(0.0, w, h, 0.0, 0.0, 100.0);

    glMatrixMode(GL_MODELVIEW);    // Set the matrix mode to object modeling

    glClearColor(0.0f, 0.0f, 0.0f, 0.0f); 
    glClearDepth(0.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear the window

    cv::Mat frame;
    captureFromWebcam(frame,capture0);


    /* OpenGL texture binding of the image loaded by DevIL  */
    GLuint texid;
    glGenTextures(1, &texid); /* Texture name generation */
    glBindTexture(GL_TEXTURE_2D, texid); /* Binding of texture name */
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); /* We will use linear interpolation for magnification filter */
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); /* We will use linear interpolation for minifying filter */
    glTexImage2D(GL_TEXTURE_2D, 0,3, frame.size().width, frame.size().height, 0, GL_RGB, GL_UNSIGNED_BYTE, 0); /* Texture specification */


    while(!glfwWindowShouldClose(window))
    {
        glfwPollEvents();

        if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
            glfwSetWindowShouldClose(window, GL_TRUE);

        // Clear color and depth buffers
       glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
       glBindTexture(GL_TEXTURE_2D,texid);
       glMatrixMode(GL_MODELVIEW);     // Operate on model-view matrix

        /* Draw a quad */
       glBegin(GL_QUADS);
           glTexCoord2i(0, 0); glVertex2i(0,   0);
           glTexCoord2i(0, 1); glVertex2i(0,   h);
           glTexCoord2i(1, 1); glVertex2i(w, h);
           glTexCoord2i(1, 0); glVertex2i(w, 0);
       glEnd();
       glFlush();
       glfwSwapBuffers(window);
    }


    releaseCapturing();
    glfwTerminate();

    return 1;
}

和其他程序

cv::VideoCapture capture0;
cv::VideoCapture capture1;

void captureFromWebcam(cv::Mat &frame, cv::VideoCapture &capture)
{
    capture.read(frame);
}

bool initializeCapturing()
{
    capture0.open(0);
    capture1.open(1);

    if(!capture0.isOpened() | !capture1.isOpened())
    {
        std::cout << "Ein oder mehrere VideoCaptures konnten nicht geöffnet werden" << std::endl;

        if(!capture0.isOpened())
            capture0.release(); 
        if(!capture1.isOpened())
            capture1.release();
        return false;
    }

    return true;
}

void releaseCapturing()
{
    capture0.release();
    capture1.release();
}

推荐答案

看起来你混合了在不同地方找到的几个代码片段.您正在请求 OpenGL 3.2 核心 配置文件.但是您使用的绘图代码是具有固定功能管道的即时模式，在核心配置文件中不可用.您基本上要求使用现代 GL 上下文，但绘图代码已完全过时，您选择的 GL 版本不再支持.

It looks like you mixed several code fragments you found at different places. You are rquesting an OpenGL 3.2 core profile. But the drawing code you are using is immediate mode with the fixed-function pipeline, which is not available in a core profile. You basically requested a modern GL context, but the drawing code is completely outdated and not supported any more by the GL version you selected.

作为快速修复，您可以简单地删除以下几行:

As a quick fix, you could simply remove the following lines:

glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);

这样做应该会为您提供一些旧的 GL 上下文或一些现代上下文的兼容性配置文件，具体取决于您使用的 GL 实现的操作系统.但是，您可以期望至少以这种方式获得 OpenGL 2.1(除非在完全不支持 GL2 的非常旧的硬件上，但即使这样对您的代码也可以).其余代码应该在这样的上下文中工作.

Doing so should provide you with some legacy GL context OR a compatibility profile of some modern context, depending on the operation system an GL implementation you use. However, you can expect from that to get at least OpenGL 2.1 that way (except on very old hardware not supporting GL2 at all, but even that would be OK for your code). The rest of the code should work in such a context.

我仍然建议您学习现代 GL，而不是您在这里使用的旧的、已弃用的遗留内容.

I still suggest that you learn mordern GL instead of the old, deprecated legacy stuff you are using here.

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