c++ - 检测方 block opencv和c++

Question

您好，我正在从事计算机视觉项目，并尝试使用来自相机的 openCV/C++ 来检测正方形。我已经从 openCV 库下载了源代码，但似乎很难失去 fps​​。有人知道如何解决这个问题吗？下面有一个关于我的测试的视频链接，请查看: http://magicbookproject.blogspot.co.uk/2012/12/detect-paper-demo.html

这是代码，刚刚在另一篇文章中找到:

void find_squares(Mat& image, vector<vector<Point> >& squares)
{
// blur will enhance edge detection
Mat blurred(image);
medianBlur(image, blurred, 9);

Mat gray0(blurred.size(), CV_8U), gray;
vector<vector<Point> > contours;

// find squares in every color plane of the image
for (int c = 0; c < 3; c++)
{
    int ch[] = {c, 0};
    mixChannels(&blurred, 1, &gray0, 1, ch, 1);

    // try several threshold levels
    const int threshold_level = 2;
    for (int l = 0; l < threshold_level; l++)
    {
        // Use Canny instead of zero threshold level!
        // Canny helps to catch squares with gradient shading
        if (l == 0)
        {
            Canny(gray0, gray, 10, 20, 3); // 

            // Dilate helps to remove potential holes between edge segments
            dilate(gray, gray, Mat(), Point(-1,-1));
        }
        else
        {
                gray = gray0 >= (l+1) * 255 / threshold_level;
        }

        // Find contours and store them in a list
        findContours(gray, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);

        // Test contours
        vector<Point> approx;
        for (size_t i = 0; i < contours.size(); i++)
        {
                // approximate contour with accuracy proportional
                // to the contour perimeter
                approxPolyDP(Mat(contours[i]), approx, arcLength(Mat(contours[i]), true)*0.02, true);

                // Note: absolute value of an area is used because
                // area may be positive or negative - in accordance with the
                // contour orientation
                if (approx.size() == 4 &&
                        fabs(contourArea(Mat(approx))) > 1000 &&
                        isContourConvex(Mat(approx)))
                {
                        double maxCosine = 0;

                        for (int j = 2; j < 5; j++)
                        {
                                double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));
                                maxCosine = MAX(maxCosine, cosine);
                        }

                        if (maxCosine < 0.3)
                                squares.push_back(approx);
                }
        }
    }
}

Answer 1

如果您不介意失去准确性，您可以加快速度。例如

// find squares in every color plane of the image
for (int c = 0; c < 3; c++)

您正在循环三个颜色平面。只需检查一种颜色(好像图像是灰度图像)，速度应该提高三倍。

也可以在没有 Canny 的情况下尝试，这很慢。设置一个use_canny参数，

 if (l == 0 && use_canny)
     {
        Canny(gray0, gray, 10, 20, 3); // 

比较有无。我得到了可以接受的结果，而且速度要快得多。