Correct HSV InRange Values for 'Red' Objects

edit

Hi,

Below I am sharing the code I created to chose HSV value easily while HSV-color segmentation ,you can use it and choose correct HSV-Range. Hope this will helpful for the user who working with HSV colour segmentation.

Code:

#include "opencv2/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include <iostream>

#define HUEMAX 179
#define SATMAX 255
#define VALMAX 255

using namespace std;
using namespace cv;

Mat HSV;
int H = 170;
int S = 200;
int V = 200;
int R = 0;
int G = 0;
int B = 0;

int MAX_H = 179;
int MAX_S = 255;
int MAX_V = 255;
int mouse_x = 0;
int mouse_y = 0;
char window_name[20] = "HSV Color Plot";

//Global variable for hsv color wheel plot
int max_hue_range = 179;
int max_step = 3; //nuber of pixel for each hue color
int wheel_width = max_hue_range * max_step;
int wheel_hight = 50;
int wheel_x = 50; //x-position of wheel
int wheel_y = 5;//y-position of wheel

//Global variable plot for satuarion-value plot
int S_V_Width = MAX_S;
int S_V_Height = MAX_S;
int S_V_x = 10;
int S_V_y = wheel_y + wheel_hight + 20;

//Global variable for HSV plot
int HSV_Width = 150;
int HSV_Height = 150;
int HSV_x = S_V_x + S_V_Width + 30;
int HSV_y = S_V_y + 50;


void onTrackbar_changed(int, void*);
static void onMouse(int event, int x, int y, int, void*);
void drawPointers(void);

int main()
{
    HSV.create(390, 640, CV_8UC3);
    HSV.setTo(Scalar(200, 0, 200));

    namedWindow(window_name);
    createTrackbar("Hue", window_name, &H, HUEMAX, onTrackbar_changed);
    createTrackbar("Saturation", window_name, &S, SATMAX, onTrackbar_changed);
    createTrackbar("Value", window_name, &V, VALMAX, onTrackbar_changed);
    onTrackbar_changed(0, 0); //initialize window

    setMouseCallback(window_name, onMouse, 0);
    while (true)
    {
        int c;
        c = waitKey(20);
        if ((char)c == 27)
        {
            break;
        }
    }

    return 0;
}

void onTrackbar_changed(int, void*) {

    //Plot color wheel.
    int hue_range = 0;
    int step = 1;
    for (int i = wheel_y; i < wheel_hight + wheel_y; i++) {
        hue_range = 0;
        for (int j = wheel_x; j < wheel_width + wheel_x; j++) {
            if (hue_range >= max_hue_range) hue_range = 0;
            if (step++ == max_step) {
                hue_range++;
                step = 1;
            }
            Vec3b pix;
            pix.val[0] = hue_range;
            pix.val[1] = 255;
            pix.val[2] = 255;


            HSV.at<Vec3b>(i, j) = pix;

        }
    }


    //Plot for saturation and value
    int sat_range = 0;
    int value_range = 255;
    for (int i = S_V_y; i < S_V_Height + S_V_y; i++) {
        value_range--;
        sat_range = 0;
        for (int j = S_V_x; j < S_V_Width + S_V_x; j++) {
            Vec3b pix;
            pix.val[0] = H;
            pix.val[1] = sat_range++;
            pix.val[2] = value_range;
            HSV.at<Vec3b>(i, j) = pix;

        }

    }

    //Plot for HSV
    Mat roi1(HSV, Rect(HSV_x, HSV_y, HSV_Width, HSV_Height));
    roi1 = Scalar(H, S, V);
    drawPointers();

    Mat RGB;
    cvtColor(HSV, RGB, COLOR_HSV2BGR);

    imshow(window_name, RGB);
    imwrite("hsv.jpg", RGB);

}

static void onMouse(int event, int x, int y, int f, void*) {
    if (f&EVENT_FLAG_LBUTTON) {
        mouse_x = x;
        mouse_y = y;
        if (((wheel_x <= x) && (x <= wheel_x + wheel_width)) && ((wheel_y <= y) && (y <= wheel_y + wheel_hight))) {
            H = (x - wheel_x) / max_step;
            setTrackbarPos("Hue", window_name, H);
        }
        else if (((S_V_x <= x) && (x <= S_V_x + S_V_Width)) && ((S_V_y <= y) && (y <= S_V_y + S_V_Height))) {

            S = x - S_V_x;
            y = y - S_V_y;
            V = 255 - y;

            setTrackbarPos("Saturation", window_name, S);
            setTrackbarPos("Value", window_name, V);
        }

    }

}

void drawPointers() {
    // Point p(S_V_x+S,S_V_y+(255-V));
    Point p(S, 255 - V ...