如何在IOS中获得完美的文档边缘检测？

Question

如果问到问题，首先很抱歉。我正在开发一个可以检测文档角落的应用程序。我现在正在使用 openCV 来检测边缘。我使用openCV实现了这一点，但我没有得到完美的结果。

我也试过BradLarson GPUImage，但我能够从这开始。

我的代码检测文档的一角但不是一个完美的结果。

   void find_squares(Mat& image, cv::vector<cv::vector<cv::Point>>&squares)
{
    // blur will enhance edge detection
    Mat blurred(image);
    //cv::resize(image, image, cvSize(0.25, 0.25));
    Mat gray0(blurred.size(), CV_8U), gray;

    //medianBlur(image, blurred, 9); //default 9;
    GaussianBlur(image, blurred, cvSize(9, 9), 2.0,2.0);

    vector<vector<cv::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 = 4;
        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(), cv::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<cv::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);
                }
            }
        }
    }
}

所以我的问题是：

1）是否有其他库可以做到这一点。

2）上面的代码有问题吗？我应该在检测之前添加一些图像处理吗？

3）BradLarson GPUImage可以这样做吗？如果它可以有用于边缘检测的样本代码源？