{

// Load the image we'll work on

IplImage* img = cvLoadImage("C:\\goal_arena.jpg");

CvSize imgSize = cvGetSize(img);

// This will hold the white parts of the image

IplImage* detected = cvCreateImage(imgSize, 8, 1);

// These hold the three channels of the loaded image

IplImage* imgBlue = cvCreateImage(imgSize, 8, 1);

IplImage* imgGreen = cvCreateImage(imgSize, 8, 1);

IplImage* imgRed = cvCreateImage(imgSize, 8, 1);

cvSplit(img, imgBlue, imgGreen, imgRed, NULL);

// Extract white parts into detected

cvAnd(imgGreen, imgBlue, detected);

cvAnd(detected, imgRed, detected);

// Morphological opening

cvErode(detected, detected);

cvDilate(detected, detected);

// Thresholding (I knew you wouldn't catch this one... so i wrote a comment here

// I mean the command can be so decieving at times)

cvThreshold(detected, detected, 100, 250, CV_THRESH_BINARY);

// Do the hough thingy

CvMat* lines = cvCreateMat(100, 1, CV_32FC2);

cvHoughLines2(detected, lines, CV_HOUGH_STANDARD, 1, 0.001, 100);

// The two endpoints for each boundary line

CvPoint left1 = cvPoint(0, 0);

CvPoint left2 = cvPoint(0, 0);

CvPoint right1 = cvPoint(0, 0);

CvPoint right2 = cvPoint(0, 0);

CvPoint top1 = cvPoint(0, 0);

CvPoint top2 = cvPoint(0, 0);

CvPoint bottom1 = cvPoint(0, 0);

CvPoint bottom2 = cvPoint(0, 0);

// Some numbers we're interested in

int numLines = lines->rows;

int numTop = 0;

int numBottom = 0;

int numLeft = 0;

int numRight = 0;

// Iterate through each line

for(int i=0;i<numLines;i++)

{

// Get the parameters for the current line

CvScalar dat = cvGet1D(lines, i);

double rho = dat.val[0];

double theta = dat.val[1];

if(theta==0.0)

{

// This is an obviously vertical line... and we can't approximate it... NEXT

continue;

}

// Convert from radians to degrees

double degrees = theta*180/(3.1412);

// Generate two points on this line (one at x=0 and one at x=image's width)

CvPoint pt1 = cvPoint(0, rho/sin(theta));

CvPoint pt2 = cvPoint(img->width, (-img->width/tan(theta)) + rho/sin(theta));

if(abs(rho)<50) // Top + left

{

if(degrees>45 && degrees<135) // Top

{

numTop++;

// The line is horizontal and near the top

top1.x+=pt1.x;

top1.y+=pt1.y;

top2.x+=pt2.x;

top2.y+=pt2.y;

}

else // left

{

numLeft++;

//The line is vertical and near the left

left1.x+=pt1.x;

left1.y+=pt1.y;

left2.x+=pt2.x;

left2.y+=pt2.y;

}

}

else // bottom+right

{

if(degrees>45 && degrees<135) // Bottom

{

numBottom++;

//The line is horizontal and near the bottom

bottom1.x+=pt1.x;

bottom1.y+=pt1.y;

bottom2.x+=pt2.x;

bottom2.y+=pt2.y;

}

else // Right

{

numRight++;

// The line is vertical and near the right

right1.x+=pt1.x;

right1.y+=pt1.y;

right2.x+=pt2.x;

right2.y+=pt2.y;

}

}

}

// we've done the adding... now the dividing to get the "averaged" point

left1.x/=numLeft;

left1.y/=numLeft;

left2.x/=numLeft;

left2.y/=numLeft;

right1.x/=numRight;

right1.y/=numRight;

right2.x/=numRight;

right2.y/=numRight;

top1.x/=numTop;

top1.y/=numTop;

top2.x/=numTop;

top2.y/=numTop;

bottom1.x/=numBottom;

bottom1.y/=numBottom;

bottom2.x/=numBottom;

bottom2.y/=numBottom;

// Render these lines onto the image

cvLine(img, left1, left2, CV_RGB(255, 0,0), 1);

cvLine(img, right1, right2, CV_RGB(255, 0,0), 1);

cvLine(img, top1, top2, CV_RGB(255, 0,0), 1);

cvLine(img, bottom1, bottom2, CV_RGB(255, 0,0), 1);

// Next, we need to figure out the four intersection points

double leftA = left2.y-left1.y;

double leftB = left1.x-left2.x;

double leftC = leftA*left1.x + leftB*left1.y;

double rightA = right2.y-right1.y;

double rightB = right1.x-right2.x;

double rightC = rightA*right1.x + rightB*right1.y;

double topA = top2.y-top1.y;

double topB = top1.x-top2.x;

double topC = topA*top1.x + topB*top1.y;

double bottomA = bottom2.y-bottom1.y;

double bottomB = bottom1.x-bottom2.x;

double bottomC = bottomA*bottom1.x + bottomB*bottom1.y;

// Intersection of left and top

double detTopLeft = leftA*topB - leftB*topA;

CvPoint ptTopLeft = cvPoint((topB*leftC - leftB*topC)/detTopLeft, (leftA*topC - topA*leftC)/detTopLeft);

// Intersection of top and right

double detTopRight = rightA*topB - rightB*topA;

CvPoint ptTopRight = cvPoint((topB*rightC-rightB*topC)/detTopRight, (rightA*topC-topA*rightC)/detTopRight);

// Intersection of right and bottom

double detBottomRight = rightA*bottomB - rightB*bottomA;

CvPoint ptBottomRight = cvPoint((bottomB*rightC-rightB*bottomC)/detBottomRight, (rightA*bottomC-bottomA*rightC)/detBottomRight);

// Intersection of bottom and left

double detBottomLeft = leftA*bottomB-leftB*bottomA;

CvPoint ptBottomLeft = cvPoint((bottomB*leftC-leftB*bottomC)/detBottomLeft, (leftA*bottomC-bottomA*leftC)/detBottomLeft);

// Render the points onto the image

cvLine(img, ptTopLeft, ptTopLeft, CV_RGB(0,255,0), 5);

cvLine(img, ptTopRight, ptTopRight, CV_RGB(0,255,0), 5);

cvLine(img, ptBottomRight, ptBottomRight, CV_RGB(0,255,0), 5);

cvLine(img, ptBottomLeft, ptBottomLeft, CV_RGB(0,255,0), 5);

// Initialize a mask

IplImage* imgMask = cvCreateImage(imgSize, 8, 3);

cvZero(imgMask);

// Generate the mask

CvPoint* pts = new CvPoint[4];

pts[0] = ptTopLeft;

pts[1] = ptTopRight;

pts[2] = ptBottomRight;

pts[3] = ptBottomLeft;

cvFillConvexPoly(imgMask, pts, 4, cvScalar(255,255,255));

// Delete anything thats outside the mask

cvAnd(img, imgMask, img);

// Show all images in windows

cvNamedWindow("Original");

cvNamedWindow("Detected");

cvShowImage("Original", img);

cvShowImage("Detected", detected);

cvWaitKey(0);

return 0;

}