--- /dev/null
+// The "Square Detector" program.
+// It loads several images sequentially and tries to find squares in
+// each image
+
+#include "opencv2/core/core.hpp"
+#include "opencv2/imgproc/imgproc.hpp"
+#include "opencv2/highgui/highgui.hpp"
+#include "opencv2/ocl/ocl.hpp"
+
+#include <iostream>
+#include <math.h>
+#include <string.h>
+
+using namespace cv;
+using namespace std;
+
+void help()
+{
+ cout <<
+ "\nA program using OCL module pyramid scaling, Canny, dilate functions; cpu contours, contour simpification and\n"
+ "memory storage (it's got it all folks) to find\n"
+ "squares in a list of images pic1-6.png\n"
+ "Returns sequence of squares detected on the image.\n"
+ "the sequence is stored in the specified memory storage\n"
+ "Call:\n"
+ "./squares\n"
+ "Using OpenCV version %s\n" << CV_VERSION << "\n" << endl;
+}
+
+
+int thresh = 50, N = 11;
+const char* wndname = "OpenCL Square Detection Demo";
+
+// helper function:
+// finds a cosine of angle between vectors
+// from pt0->pt1 and from pt0->pt2
+double angle( Point pt1, Point pt2, Point pt0 )
+{
+ double dx1 = pt1.x - pt0.x;
+ double dy1 = pt1.y - pt0.y;
+ double dx2 = pt2.x - pt0.x;
+ double dy2 = pt2.y - pt0.y;
+ return (dx1*dx2 + dy1*dy2)/sqrt((dx1*dx1 + dy1*dy1)*(dx2*dx2 + dy2*dy2) + 1e-10);
+}
+
+// returns sequence of squares detected on the image.
+// the sequence is stored in the specified memory storage
+void findSquares( const Mat& image, vector<vector<Point> >& squares )
+{
+ squares.clear();
+
+ Mat pyr, timg, gray0(image.size(), CV_8U), gray;
+ cv::ocl::oclMat pyr_ocl, timg_ocl, gray0_ocl(gray0), gray_ocl;
+
+ // down-scale and upscale the image to filter out the noise
+ ocl::pyrDown(ocl::oclMat(image), pyr_ocl);
+ ocl::pyrUp(pyr_ocl, timg_ocl);
+ timg = Mat(timg_ocl);
+
+ 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(&timg, 1, &gray0, 1, ch, 1);
+
+ // try several threshold levels
+ for( int l = 0; l < N; l++ )
+ {
+ // hack: use Canny instead of zero threshold level.
+ // Canny helps to catch squares with gradient shading
+ if( l == 0 )
+ {
+ // do canny on OpenCL device
+ // apply Canny. Take the upper threshold from slider
+ // and set the lower to 0 (which forces edges merging)
+ cv::ocl::Canny(gray0_ocl, gray_ocl, 0, thresh, 5);
+ // dilate canny output to remove potential
+ // holes between edge segments
+ ocl::dilate(gray0_ocl, gray_ocl, Mat(), Point(-1,-1));
+ gray = Mat(gray_ocl);
+ }
+ else
+ {
+ // apply threshold if l!=0:
+ // tgray(x,y) = gray(x,y) < (l+1)*255/N ? 255 : 0
+ gray = gray0 >= (l+1)*255/N;
+ }
+
+ // find contours and store them all as a list
+ findContours(gray, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);
+
+ vector<Point> approx;
+
+ // test each contour
+ 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);
+
+ // square contours should have 4 vertices after approximation
+ // relatively large area (to filter out noisy contours)
+ // and be convex.
+ // 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++ )
+ {
+ // find the maximum cosine of the angle between joint edges
+ double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));
+ maxCosine = MAX(maxCosine, cosine);
+ }
+
+ // if cosines of all angles are small
+ // (all angles are ~90 degree) then write quandrange
+ // vertices to resultant sequence
+ if( maxCosine < 0.3 )
+ squares.push_back(approx);
+ }
+ }
+ }
+ }
+}
+
+
+// the function draws all the squares in the image
+void drawSquares( Mat& image, const vector<vector<Point> >& squares )
+{
+ for( size_t i = 0; i < squares.size(); i++ )
+ {
+ const Point* p = &squares[i][0];
+ int n = (int)squares[i].size();
+ polylines(image, &p, &n, 1, true, Scalar(0,255,0), 3, CV_AA);
+ }
+
+ imshow(wndname, image);
+}
+
+
+int main(int /*argc*/, char** /*argv*/)
+{
+
+ //ocl::setBinpath("F:/kernel_bin");
+ vector<ocl::Info> info;
+ CV_Assert(ocl::getDevice(info));
+
+ static const char* names[] = { "pic1.png", "pic2.png", "pic3.png",
+ "pic4.png", "pic5.png", "pic6.png", 0 };
+ help();
+ namedWindow( wndname, 1 );
+ vector<vector<Point> > squares;
+
+ for( int i = 0; names[i] != 0; i++ )
+ {
+ Mat image = imread(names[i], 1);
+ if( image.empty() )
+ {
+ cout << "Couldn't load " << names[i] << endl;
+ continue;
+ }
+
+ findSquares(image, squares);
+ drawSquares(image, squares);
+
+ int c = waitKey();
+ if( (char)c == 27 )
+ break;
+ }
+
+ return 0;
+}