How to properly apply Hough Circle Transform in iOS environment? - ios

Question

First of, I have no experience working in Objective C++.
Like the subjects states, I am trying to implement OpenCV (v3.4.2) Hough Circle Transform into images capture via iOS device. So far, I am able to make the captured photo greyscale. However, when I try to apply circle transform, app crashes. Also, there are syntax errors when I try to draw the recognized circles.
OpenCV Guide I am following.
Thank you for your time.
#import <opencv2/opencv.hpp>
#import <opencv2/imgcodecs/ios.h>
#import "GoCalc2-Bridging-Header.h"
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#implementation ImageConverter : NSObject
+(UIImage *)ConvertImage:(UIImage *)image {
cv::Mat mat;
UIImageToMat(image, mat);
cv::Mat gray;
cv::cvtColor(mat, gray, CV_RGB2GRAY);
cv::Mat bin;
cv::threshold(gray, bin, 0, 255, cv::THRESH_BINARY | cv::THRESH_OTSU);
// Apply a Median blur to reduce noise and avoid false circle detection
cv::medianBlur(mat, gray, 5);
// Proceed to apply Hough Circle Transform
std::vector<cv::Vec3f> circles;
HoughCircles(gray, circles, cv::HOUGH_GRADIENT, 1,
gray.rows/16, // change this value to detect circles with different distances to each other
100, 30, 1, 30 // change the last two parameters
// (min_radius & max_radius) to detect larger circles
);
// Draw the detected circles
for( size_t i = 0; i < circles.size(); i++ )
{
Vec3i c = circles[i];
Point center = Point(c[0], c[1]); // ERROR HERE: No matching constructor for initialization of 'Point'
// circle center
circle( src, center, 1, Scalar(0,100,100), 3, LINE_AA); // ERROR HERE: Use of undeclared identifier 'LINE_AA' and Use of undeclared identifier 'src'
// circle outline
int radius = c[2];
circle( src, center, radius, Scalar(255,0,255), 3, LINE_AA); // ERROR HERE: Use of undeclared identifier 'LINE_AA' and Use of undeclared identifier 'src'
}
// Display the detected circle(s) and wait for the user to exit the program
imshow("detected circles", mat);
cv::waitKey();
UIImage *binImg = MatToUIImage(bin);
return binImg;
}
#end

Answer 1

Have you tried removing LINE_AA?
This is what I have done in my app circle( img, center, 1, cvScalar(255,255,255), 3);.
Instead of Vec3i c = circles[i]; you may want to try cv::Vec3i c = circles[i];
hope it will help