| OpenCV 3.4.3 Open Source Computer Vision

samples/cpp/fitellipse.cpp

An example using the fitEllipse technique

/********************************************************************************
*
*
* This program is demonstration for ellipse fitting. Program finds
* contours and approximate it by ellipses using three methods.
* 1: OpenCV's original method fitEllipse which implements Fitzgibbon 1995 method.
* 2: The Approximate Mean Square (AMS) method fitEllipseAMS proposed by Taubin 1991
* 3: The Direct least square (Direct) method fitEllipseDirect proposed by Fitzgibbon1999.
*
* Trackbar specify threshold parameter.
*
* White lines is contours/input points and the true ellipse used to generate the data.
* 1: Blue lines is fitting ellipses using openCV's original method.
* 2: Green lines is fitting ellipses using the AMS method.
* 3: Red lines is fitting ellipses using the Direct method.
*
*
* Original Author: Denis Burenkov
* AMS and Direct Methods Author: Jasper Shemilt
*
*
********************************************************************************/
#include "opencv2/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include <iostream>
using namespace cv;
using namespace std;
class canvas{
public:
bool setupQ;
cv::Point origin;
cv::Point corner;
int minDims,maxDims;
double scale;
int rows, cols;
cv::Mat img;
void init(int minD, int maxD){
// Initialise the canvas with minimum and maximum rows and column sizes.
minDims = minD; maxDims = maxD;
origin = cv::Point(0,0);
corner = cv::Point(0,0);
scale = 1.0;
rows = 0;
cols = 0;
setupQ = false;
}
void stretch(cv::Point2f min, cv::Point2f max){
// Stretch the canvas to include the points min and max.
if(setupQ){
if(corner.x < max.x){corner.x = (int)(max.x + 1.0);};
if(corner.y < max.y){corner.y = (int)(max.y + 1.0);};
if(origin.x > min.x){origin.x = (int) min.x;};
if(origin.y > min.y){origin.y = (int) min.y;};
} else {
origin = cv::Point((int)min.x, (int)min.y);
corner = cv::Point((int)(max.x + 1.0), (int)(max.y + 1.0));
}
int c = (int)(scale*((corner.x + 1.0) - origin.x));
if(c<minDims){
scale = scale * (double)minDims/(double)c;
} else {
if(c>maxDims){
scale = scale * (double)maxDims/(double)c;
}
}
int r = (int)(scale*((corner.y + 1.0) - origin.y));
if(r<minDims){
scale = scale * (double)minDims/(double)r;
} else {
if(r>maxDims){
scale = scale * (double)maxDims/(double)r;
}
}
cols = (int)(scale*((corner.x + 1.0) - origin.x));
rows = (int)(scale*((corner.y + 1.0) - origin.y));
setupQ = true;
}
void stretch(vector<Point2f> pts)
{ // Stretch the canvas so all the points pts are on the canvas.
cv::Point2f min = pts[0];
cv::Point2f max = pts[0];
for(size_t i=1; i < pts.size(); i++){
Point2f pnt = pts[i];
if(max.x < pnt.x){max.x = pnt.x;};
if(max.y < pnt.y){max.y = pnt.y;};
if(min.x > pnt.x){min.x = pnt.x;};
if(min.y > pnt.y){min.y = pnt.y;};
};
stretch(min, max);
}
void stretch(cv::RotatedRect box)
{ // Stretch the canvas so that the rectangle box is on the canvas.
cv::Point2f min = box.center;
cv::Point2f max = box.center;
cv::Point2f vtx[4];
box.points(vtx);
for( int i = 0; i < 4; i++ ){
cv::Point2f pnt = vtx[i];
if(max.x < pnt.x){max.x = pnt.x;};
if(max.y < pnt.y){max.y = pnt.y;};
if(min.x > pnt.x){min.x = pnt.x;};
if(min.y > pnt.y){min.y = pnt.y;};
}
stretch(min, max);
}
void drawEllipseWithBox(cv::RotatedRect box, cv::Scalar color, int lineThickness)
{
if(img.empty()){
stretch(box);
img = cv::Mat::zeros(rows,cols,CV_8UC3);
}
box.center = scale * cv::Point2f(box.center.x - origin.x, box.center.y - origin.y);
box.size.width = (float)(scale * box.size.width);
box.size.height = (float)(scale * box.size.height);
ellipse(img, box, color, lineThickness, LINE_AA);
Point2f vtx[4];
box.points(vtx);
for( int j = 0; j < 4; j++ ){
line(img, vtx[j], vtx[(j+1)%4], color, lineThickness, LINE_AA);
}
}
void drawPoints(vector<Point2f> pts, cv::Scalar color)
{
if(img.empty()){
stretch(pts);
img = cv::Mat::zeros(rows,cols,CV_8UC3);
}
for(size_t i=0; i < pts.size(); i++){
Point2f pnt = scale * cv::Point2f(pts[i].x - origin.x, pts[i].y - origin.y);
img.at<cv::Vec3b>(int(pnt.y), int(pnt.x))[0] = (uchar)color[0];
img.at<cv::Vec3b>(int(pnt.y), int(pnt.x))[1] = (uchar)color[1];
img.at<cv::Vec3b>(int(pnt.y), int(pnt.x))[2] = (uchar)color[2];
};
}
void drawLabels( std::vector<std::string> text, std::vector<cv::Scalar> colors)
{
if(img.empty()){
img = cv::Mat::zeros(rows,cols,CV_8UC3);
}
int vPos = 0;
for (size_t i=0; i < text.size(); i++) {
cv::Scalar color = colors[i];
std::string txt = text[i];
Size textsize = getTextSize(txt, FONT_HERSHEY_COMPLEX, 1, 1, 0);
vPos += (int)(1.3 * textsize.height);
Point org((img.cols - textsize.width), vPos);
cv::putText(img, txt, org, FONT_HERSHEY_COMPLEX, 1, color, 1, LINE_8);
}
}
};
static void help()
{
cout <<
"\nThis program is demonstration for ellipse fitting. The program finds\n"
"contours and approximate it by ellipses. Three methods are used to find the \n"
"elliptical fits: fitEllipse, fitEllipseAMS and fitEllipseDirect.\n"
"Call:\n"
"./fitellipse [image_name -- Default ../data/stuff.jpg]\n" << endl;
}
int sliderPos = 70;
Mat image;
bool fitEllipseQ, fitEllipseAMSQ, fitEllipseDirectQ;
cv::Scalar fitEllipseColor = Scalar(255, 0, 0);
cv::Scalar fitEllipseAMSColor = Scalar( 0,255, 0);
cv::Scalar fitEllipseDirectColor = Scalar( 0, 0,255);
cv::Scalar fitEllipseTrueColor = Scalar(255,255,255);
void processImage(int, void*);
int main( int argc, char** argv )
{
fitEllipseQ = true;
fitEllipseAMSQ = true;
fitEllipseDirectQ = true;
cv::CommandLineParser parser(argc, argv,"{help h||}{@image|../data/ellipses.jpg|}");
if (parser.has("help"))
{
help();
return 0;
}
string filename = parser.get<string>("@image");
image = imread(filename, 0);
if( image.empty() )
{
cout << "Couldn't open image " << filename << "\n";
return 0;
}
imshow("source", image);
namedWindow("result", WINDOW_NORMAL );
// Create toolbars. HighGUI use.
createTrackbar( "threshold", "result", &sliderPos, 255, processImage );
processImage(0, 0);
// Wait for a key stroke; the same function arranges events processing
waitKey();
return 0;
}
// Define trackbar callback function. This function finds contours,
// draws them, and approximates by ellipses.
void processImage(int /*h*/, void*)
{
RotatedRect box, boxAMS, boxDirect;
vector<vector<Point> > contours;
Mat bimage = image >= sliderPos;
findContours(bimage, contours, RETR_LIST, CHAIN_APPROX_NONE);
canvas paper;
paper.init(int(0.8*MIN(bimage.rows, bimage.cols)), int(1.2*MAX(bimage.rows, bimage.cols)));
paper.stretch(cv::Point2f(0.0f, 0.0f), cv::Point2f((float)(bimage.cols+2.0), (float)(bimage.rows+2.0)));
std::vector<std::string> text;
std::vector<cv::Scalar> color;
if (fitEllipseQ) {
text.push_back("OpenCV");
color.push_back(fitEllipseColor);
}
if (fitEllipseAMSQ) {
text.push_back("AMS");
color.push_back(fitEllipseAMSColor);
}
if (fitEllipseDirectQ) {
text.push_back("Direct");
color.push_back(fitEllipseDirectColor);
}
paper.drawLabels(text, color);
int margin = 2;
vector< vector<Point2f> > points;
for(size_t i = 0; i < contours.size(); i++)
{
size_t count = contours[i].size();
if( count < 6 )
continue;
Mat pointsf;
Mat(contours[i]).convertTo(pointsf, CV_32F);
vector<Point2f>pts;
for (int j = 0; j < pointsf.rows; j++) {
Point2f pnt = Point2f(pointsf.at<float>(j,0), pointsf.at<float>(j,1));
if ((pnt.x > margin && pnt.y > margin && pnt.x < bimage.cols-margin && pnt.y < bimage.rows-margin)) {
if(j%20==0){
pts.push_back(pnt);
}
}
}
points.push_back(pts);
}
for(size_t i = 0; i < points.size(); i++)
{
vector<Point2f> pts = points[i];
if (pts.size()<=5) {
continue;
}
if (fitEllipseQ) {
box = fitEllipse(pts);
if( MAX(box.size.width, box.size.height) > MIN(box.size.width, box.size.height)*30 ||
MAX(box.size.width, box.size.height) <= 0 ||
MIN(box.size.width, box.size.height) <= 0){continue;};
}
if (fitEllipseAMSQ) {
boxAMS = fitEllipseAMS(pts);
if( MAX(boxAMS.size.width, boxAMS.size.height) > MIN(boxAMS.size.width, boxAMS.size.height)*30 ||
MAX(box.size.width, box.size.height) <= 0 ||
MIN(box.size.width, box.size.height) <= 0){continue;};
}
if (fitEllipseDirectQ) {
boxDirect = fitEllipseDirect(pts);
if( MAX(boxDirect.size.width, boxDirect.size.height) > MIN(boxDirect.size.width, boxDirect.size.height)*30 ||
MAX(box.size.width, box.size.height) <= 0 ||
MIN(box.size.width, box.size.height) <= 0 ){continue;};
}
if (fitEllipseQ) {
paper.drawEllipseWithBox(box, fitEllipseColor, 3);
}
if (fitEllipseAMSQ) {
paper.drawEllipseWithBox(boxAMS, fitEllipseAMSColor, 2);
}
if (fitEllipseDirectQ) {
paper.drawEllipseWithBox(boxDirect, fitEllipseDirectColor, 1);
}
paper.drawPoints(pts, cv::Scalar(255,255,255));
}
imshow("result", paper.img);
}