Open Source Computer Vision Library https://opencv.org/
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// The "Square Detector" program.
// It loads several images sequentially and tries to find squares in
// each image
#include "opencv2/core.hpp"
#include "opencv2/core/utility.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;
#define ACCURACY_CHECK 1
#if ACCURACY_CHECK
// check if two vectors of vector of points are near or not
// prior assumption is that they are in correct order
static bool checkPoints(
vector< vector<Point> > set1,
vector< vector<Point> > set2,
int maxDiff = 5)
{
if(set1.size() != set2.size())
{
return false;
}
for(vector< vector<Point> >::iterator it1 = set1.begin(), it2 = set2.begin();
it1 < set1.end() && it2 < set2.end(); it1 ++, it2 ++)
{
vector<Point> pts1 = *it1;
vector<Point> pts2 = *it2;
if(pts1.size() != pts2.size())
{
return false;
}
for(size_t i = 0; i < pts1.size(); i ++)
{
Point pt1 = pts1[i], pt2 = pts2[i];
if(std::abs(pt1.x - pt2.x) > maxDiff ||
std::abs(pt1.y - pt2.y) > maxDiff)
{
return false;
}
}
}
return true;
}
#endif
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
static 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
static void findSquares( const Mat& image, vector<vector<Point> >& squares )
{
squares.clear();
Mat pyr, timg, gray0(image.size(), CV_8U), gray;
// down-scale and upscale the image to filter out the noise
pyrDown(image, pyr, Size(image.cols/2, image.rows/2));
pyrUp(pyr, timg, image.size());
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 )
{
// apply Canny. Take the upper threshold from slider
// and set the lower to 0 (which forces edges merging)
Canny(gray0, gray, 0, thresh, 5);
// dilate canny output to remove potential
// holes between edge segments
dilate(gray, gray, Mat(), Point(-1,-1));
}
else
{
// apply threshold if l!=0:
// tgray(x,y) = gray(x,y) < (l+1)*255/N ? 255 : 0
cv::threshold(gray0, gray, (l+1)*255/N, 255, THRESH_BINARY);
}
// find contours and store them all as a list
findContours(gray, contours, RETR_LIST, 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);
}
}
}
}
}
// returns sequence of squares detected on the image.
// the sequence is stored in the specified memory storage
static void findSquares_ocl( const Mat& image, vector<vector<Point> >& squares )
{
squares.clear();
Mat gray;
cv::ocl::oclMat pyr_ocl, timg_ocl, gray0_ocl, 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);
vector<vector<Point> > contours;
vector<cv::ocl::oclMat> gray0s;
ocl::split(timg_ocl, gray0s); // split 3 channels into a vector of oclMat
// find squares in every color plane of the image
for( int c = 0; c < 3; c++ )
{
gray0_ocl = gray0s[c];
// 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(gray_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
cv::ocl::threshold(gray0_ocl, gray_ocl, (l+1)*255/N, 255, THRESH_BINARY);
gray = gray_ocl;
}
// find contours and store them all as a list
findContours(gray, contours, RETR_LIST, 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
static 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, LINE_AA);
}
}
// draw both pure-C++ and ocl square results onto a single image
static Mat drawSquaresBoth( const Mat& image,
const vector<vector<Point> >& sqsCPP,
const vector<vector<Point> >& sqsOCL
)
{
Mat imgToShow(Size(image.cols * 2, image.rows), image.type());
Mat lImg = imgToShow(Rect(Point(0, 0), image.size()));
Mat rImg = imgToShow(Rect(Point(image.cols, 0), image.size()));
image.copyTo(lImg);
image.copyTo(rImg);
drawSquares(lImg, sqsCPP);
drawSquares(rImg, sqsOCL);
float fontScale = 0.8f;
Scalar white = Scalar::all(255), black = Scalar::all(0);
putText(lImg, "C++", Point(10, 20), FONT_HERSHEY_COMPLEX_SMALL, fontScale, black, 2);
putText(rImg, "OCL", Point(10, 20), FONT_HERSHEY_COMPLEX_SMALL, fontScale, black, 2);
putText(lImg, "C++", Point(10, 20), FONT_HERSHEY_COMPLEX_SMALL, fontScale, white, 1);
putText(rImg, "OCL", Point(10, 20), FONT_HERSHEY_COMPLEX_SMALL, fontScale, white, 1);
return imgToShow;
}
int main(int argc, char** argv)
{
const char* keys =
"{ i | input | | specify input image }"
"{ o | output | squares_output.jpg | specify output save path}";
CommandLineParser cmd(argc, argv, keys);
string inputName = cmd.get<string>("i");
string outfile = cmd.get<string>("o");
if(inputName.empty())
{
cout << "Available options:" << endl;
cmd.printMessage();
return 0;
}
int iterations = 10;
namedWindow( wndname, 1 );
vector<vector<Point> > squares_cpu, squares_ocl;
Mat image = imread(inputName, 1);
if( image.empty() )
{
cout << "Couldn't load " << inputName << endl;
return -1;
}
int j = iterations;
int64 t_ocl = 0, t_cpp = 0;
//warm-ups
cout << "warming up ..." << endl;
findSquares(image, squares_cpu);
findSquares_ocl(image, squares_ocl);
#if ACCURACY_CHECK
cout << "Checking ocl accuracy ... " << endl;
cout << (checkPoints(squares_cpu, squares_ocl) ? "Pass" : "Failed") << endl;
#endif
do
{
int64 t_start = cv::getTickCount();
findSquares(image, squares_cpu);
t_cpp += cv::getTickCount() - t_start;
t_start = cv::getTickCount();
findSquares_ocl(image, squares_ocl);
t_ocl += cv::getTickCount() - t_start;
cout << "run loop: " << j << endl;
}
while(--j);
cout << "cpp average time: " << 1000.0f * (double)t_cpp / getTickFrequency() / iterations << "ms" << endl;
cout << "ocl average time: " << 1000.0f * (double)t_ocl / getTickFrequency() / iterations << "ms" << endl;
Mat result = drawSquaresBoth(image, squares_cpu, squares_ocl);
imshow(wndname, result);
imwrite(outfile, result);
waitKey(0);
return 0;
}