OpenGL不喜欢OpenCV调整大小

我想使用opencv mat数据作为opengl纹理 . 我正在开发一个Qt4.8应用程序(但通过qimage是我真正不需要的)扩展QGLWidget . 但有些事情是错的..

首先是截图中的问题,然后是我正在使用的代码 .

如果我没有调整cv :: Mat(从视频中抓取)的大小,一切都还可以 . 如果我将它缩放为维度的一半(scaleFactor = 2),一切都可以 . 如果比例因子是2.8或2.9 ..一切都很好 . 但是..在某种程度上,因为它是错误的 .

这里有一个漂亮的红色背景截图,用于理解opengl quad维度:

scaleFactor = 2
enter image description here

scaleFactor = 2.8
enter image description here

scaleFactor = 3
enter image description here

scaleFactor = 3.2
enter image description here

现在是paint方法的代码 . 我找到了将cv :: Mat数据复制到this nice blog post的gl纹理中的代码 .

void VideoViewer::paintGL()
{
    glClear (GL_COLOR_BUFFER_BIT);
    glClearColor (1.0, 0.0, 0.0, 1.0);

    glEnable(GL_BLEND);

    // Use a simple blendfunc for drawing the background
    glBlendFunc(GL_ONE, GL_ZERO);

    if (!cvFrame.empty()) {
        glEnable(GL_TEXTURE_2D);

        GLuint tex = matToTexture(cvFrame);
        glBindTexture(GL_TEXTURE_2D, tex);

        glBegin(GL_QUADS);
        glTexCoord2f(1, 1); glVertex2f(0, cvFrame.size().height);
        glTexCoord2f(1, 0); glVertex2f(0, 0);
        glTexCoord2f(0, 0); glVertex2f(cvFrame.size().width, 0);
        glTexCoord2f(0, 1); glVertex2f(cvFrame.size().width, cvFrame.size().height);
        glEnd();

        glDeleteTextures(1, &tex);
        glDisable(GL_TEXTURE_2D);

        glFlush();
    }
}

GLuint VideoViewer::matToTexture(cv::Mat &mat, GLenum minFilter, GLenum magFilter, GLenum wrapFilter)
{
    // http://r3dux.org/2012/01/how-to-convert-an-opencv-cvmat-to-an-opengl-texture/

    // Generate a number for our textureID's unique handle
    GLuint textureID;
    glGenTextures(1, &textureID);

    // Bind to our texture handle
    glBindTexture(GL_TEXTURE_2D, textureID);

    // Catch silly-mistake texture interpolation method for magnification
    if (magFilter == GL_LINEAR_MIPMAP_LINEAR  ||
        magFilter == GL_LINEAR_MIPMAP_NEAREST ||
        magFilter == GL_NEAREST_MIPMAP_LINEAR ||
        magFilter == GL_NEAREST_MIPMAP_NEAREST)
    {
        std::cout << "VideoViewer::matToTexture > "
                  << "You can't use MIPMAPs for magnification - setting filter to GL_LINEAR"
                  << std::endl;
        magFilter = GL_LINEAR;
    }

    // Set texture interpolation methods for minification and magnification
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, minFilter);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, magFilter);

    // Set texture clamping method
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrapFilter);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrapFilter);

    // Set incoming texture format to:
    // GL_BGR       for CV_CAP_OPENNI_BGR_IMAGE,
    // GL_LUMINANCE for CV_CAP_OPENNI_DISPARITY_MAP,
    // Work out other mappings as required ( there's a list in comments in main() )
    GLenum inputColourFormat = GL_BGR;
    if (mat.channels() == 1)
    {
        inputColourFormat = GL_LUMINANCE;
    }

    // Create the texture
    glTexImage2D(GL_TEXTURE_2D,     // Type of texture
                 0,                 // Pyramid level (for mip-mapping) - 0 is the top level
                 GL_RGB,            // Internal colour format to convert to
                 mat.cols,          // Image width  i.e. 640 for Kinect in standard mode
                 mat.rows,          // Image height i.e. 480 for Kinect in standard mode
                 0,                 // Border width in pixels (can either be 1 or 0)
                 inputColourFormat, // Input image format (i.e. GL_RGB, GL_RGBA, GL_BGR etc.)
                 GL_UNSIGNED_BYTE,  // Image data type
                 mat.ptr());        // The actual image data itself

    return textureID;
}

以及如何加载和缩放cv :: Mat:

void VideoViewer::retriveScaledFrame()
{
    video >> cvFrame;

    cv::Size s = cv::Size(cvFrame.size().width/scaleFactor, cvFrame.size().height/scaleFactor);
    cv::resize(cvFrame, cvFrame, s);
}

有时候图像被正确渲染有时不是..为什么?可以肯定的是,opencv和opengl之间的像素存储顺序不匹配有问题 . 但是,如何解决它?为什么有时候可以,有时候没有?

回答(1)

2 years ago

是的,它是内存中像素存储的问题 . OpenCV和OpenGL可以以不同的方式存储像素,我必须更好地理解它是如何工作的 .

在OpenGL中,您可以使用 glPixelStoreiGL_UNPACK_ALIGNMENTGL_UNPACK_ROW_LENGTH 指定这些参数 .

关于这个的一个很好的答案可以找到here .