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how can merge two lines to create a ROI

asked 2018-06-03 16:17:46 -0500

biza gravatar image

updated 2018-06-03 16:22:57 -0500

I already solve part of the problem, but i need to close the lines vertically, how can i solve this situation?

#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
using namespace cv;
using namespace std;
int main(int argc, char** argv){
    Mat input = imread("bat.png");
    // convert to HSV color space
    Mat hsvImage;
    cvtColor(input, hsvImage, CV_BGR2HSV);

    // split the channels
    std::vector<cv::Mat> hsvChannels;
    split(hsvImage, hsvChannels);

    // hue channels tells you the color tone, if saturation and value aren't too low.

    // red color is a special case, because the hue space is circular and red is exactly at the beginning/end of the circle.
    // in literature, hue space goes from 0 to 360 degrees, but OpenCV rescales the range to 0 up to 180, because 360 does not fit in a single byte. Alternatively there is another mode where 0..360 is rescaled to 0..255 but this isn't as common.
    int hueValue = 65; // red color
    int hueRange =  1; // how much difference from the desired color we want to include to the result If you increase this value, for example a red color would detect some orange values, too.

    int minSaturation = 20; // I'm not sure which value is good here...
    int minValue = 0; // not sure whether 50 is a good min value here...

    Mat hueImage = hsvChannels[0]; // [hue, saturation, value]

    // is the color within the lower hue range?
    Mat hueMask;
    inRange(hueImage, hueValue - hueRange, hueValue + hueRange, hueMask);

    // if the desired color is near the border of the hue space, check the other side too:
    // TODO: this won't work if "hueValue + hueRange > 180" - maybe use two different if-cases instead... with int lowerHueValue = hueValue - 180
    if (hueValue - hueRange < 0 || hueValue + hueRange > 180)
    {
        Mat hueMaskUpper;
        int upperHueValue = hueValue + 180; // in reality this would be + 360 instead
        inRange(hueImage, upperHueValue - hueRange, upperHueValue + hueRange, hueMaskUpper);

        // add this mask to the other one
        hueMask = hueMask | hueMaskUpper;
    }

    // now we have to filter out all the pixels where saturation and value do not fit the limits:
    Mat saturationMask = hsvChannels[1] > minSaturation;
    Mat valueMask = hsvChannels[2] > minValue;

    hueMask = (hueMask & saturationMask) & valueMask;

    imshow("desired color", hueMask);

    // now perform the line detection
    std::vector<cv::Vec4i> lines;
    HoughLinesP(hueMask, lines, 1, CV_PI / 360, 50, 50, 10);

    // draw the result as big green lines:
    for (unsigned int i = 0; i < lines.size(); ++i)
    {
        line(input, cv::Point(lines[i][0], lines[i][1]), cv::Point(lines[i][2], lines[i][3]), cv::Scalar(255, 255, 0), 2);
        cout << Point(lines[i][0], lines[i][1]) << "END" << Point(lines[i][2], lines[i][3]) <<endl;
    }

    imwrite("mask.png", hueMask);
    imwrite("detection.png", input);
    imshow("input", input);
    waitKey(0);
    return 0;
}

This is my original image, now I need to merge the points to form a ROI.image description

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answered 2018-06-04 01:36:34 -0500

berak gravatar image

you could get the boundingRect for the endpoints of your lines, like this:

vector<Point> pts;
for (unsigned int i = 0; i < lines.size(); ++i)
{
    pts.push_back( Point(lines[i][0], lines[i][1]) );
    pts.push_back( Point(lines[i][2], lines[i][3]) );
}
Rect box = boundingRect(pts);
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Asked: 2018-06-03 16:17:46 -0500

Seen: 229 times

Last updated: Jun 04 '18