检测具有不同背景的图像中文档的角落

问题描述

我正在构建文档扫描仪应用程序，需要检测图像中文档的角点以进行裁剪。 到目前为止，我的代码仅在图像背景较暗时有效。 但我想在所有背景下使用它。

这是我的代码

vector<Point> getPoints(Mat image)
{
      int width = image.size().width;
          int height = image.size().height;
          Mat image_proc = image.clone();
          vector<vector<Point> > squares;
          // blur will enhance edge detection
          Mat blurred(image_proc);
          cvtColor(image_proc,image_proc,CV_BGR2GRAY);
          medianBlur(image_proc,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,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,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);
                      }
                  }
              }

              double largest_area = -1;
              int largest_contour_index = 0;
              for(int i=0;i<squares.size();i++)
              {
                  double a =contourArea(squares[i],false);
                  if(a>largest_area)
                  {
                      largest_area = a;
                      largest_contour_index = i;
                  }
              }

              __android_log_print(ANDROID_LOG_VERBOSE,APPNAME,"Scaning size() %d",squares.size());
              vector<Point> points;
              if(squares.size() > 0)
              {
                  points = squares[largest_contour_index];
              }
              else
              {
                  points.push_back(Point(0,0));
                  points.push_back(Point(width,0));
                  points.push_back(Point(0,height));
                  points.push_back(Point(width,height));
              }

              return points;
   }

上面的函数返回图像内文档的角。

解决方法

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