[OpenCV] 이미지 윈도우 상에서 마우스 이벤트 감지하기

이번 포스팅에서는 OpenCV의 마우스 콜백(Callback) 함수를 이용하여 이미지 윈도우 상에서 마우스 이벤트를 감지하는 방법에 대하여 알아보도록 하겠습니다.

OpenCV의 마우스 콜백함수는 setMouseCall 이며, 함수의 프로토타입은 다음과 같습니다:

void cv::setMouseCallback (
    const String &  winname,
    MouseCallback   onMouse,
    void *  userdata = 0 
)

파라미터들:

winname 윈도우의 이름

onMouse 마우스 콜백 함수 이름

userdata         콜백에 전달되는 옵션 파라미터

onMouse는 마우스 콜백 함수 이름인데 파라미터들은 다음과 같이 정의됩니다:

void onMouse(
    int event,
    int x,
    int y,
    int flags,
    void* userdata
)

Parameter	Description
event	마우스 이벤트 타입.  EVENT_MOUSEMOVE  EVENT_LBUTTONDOWN  EVENT_RBUTTONDOWN  EVENT_MBUTTONDOWN  EVENT_LBUTTONUP  EVENT_RBUTTONUP  EVENT_MBUTTONUP  EVENT_LBUTTONDBLCLK  EVENT_RBUTTONDBLCLK  EVENT_MBUTTONDBLCLK
x	마우스 이벤트의 x좌표
y	마우스 이벤트의 y좌표
flags	마우스 이벤트가 발생할 때의 특정 조건.  EVENT_FLAG_LBUTTON  EVENT_FLAG_RBUTTON  EVENT_FLAG_MBUTTON  EVENT_FLAG_CTRLKEY  EVENT_FLAG_SHIFTKEY  EVENT_FLAG_ALTKEY
userdata	setMouseCallback 함수로 전달되는 포인터

Example 1

#include "opencv2/highgui/highgui.hpp"
#include <iostream>
 
using namespace std;
using namespace cv;
 
 
/*/////////////////////////////////////
@ function: CallBackFunc
*//////////////////////////////////////
void CallBackFunc( int event, int x, int y, int flags, void* userdata )
{
    if ( event == EVENT_LBUTTONDOWN )
    {
        std::cout << "Left button of the mouse is clicked - position (" << x << ", " << y << ")" << std::endl;
    }
    else if ( event == EVENT_RBUTTONDOWN )
    {
        std::cout << "Right button of the mouse is clicked - position (" << x << ", " << y << ")" << std::endl;
    }
    else if ( event == EVENT_MBUTTONDOWN )
    {
        std::cout << "Middle button of the mouse is clicked - position (" << x << ", " << y << ")" << std::endl;
    }
    else if ( event == EVENT_MOUSEMOVE )
    {
        std::cout << "Mouse move over the window - position (" << x << ", " << y << ")" << std::endl;
    }
    else if ( event == EVENT_LBUTTONUP )
    {
        std::cout << "Left button of the mouse is released - position (" << x << ", " << y << ")" << std::endl;
    }
    else if ( event == EVENT_RBUTTONUP )
    {
        std::cout << "Right button of the mouse is released - position (" << x << ", " << y << ")" << std::endl;
    }
    else if ( event == EVENT_MBUTTONUP )
    {
        std::cout << "Middle button of the mouse is released - position (" << x << ", " << y << ")" << std::endl;
    }
    else if ( event == EVENT_LBUTTONDBLCLK )
    {
        std::cout << "Left button of the mouse is double-clicked - position (" << x << ", " << y << ")" << std::endl;
    }
    else if ( event == EVENT_RBUTTONDBLCLK )
    {
        std::cout << "Right button of the mouse is double-clicked - position (" << x << ", " << y << ")" << std::endl;
    }
    else if ( event == EVENT_MBUTTONDBLCLK )
    {
        std::cout << "Middle button of the mouse is double-clicked - position (" << x << ", " << y << ")" << std::endl;
    }
 
    if ( flags & CV_EVENT_FLAG_LBUTTON )
    {
        std::cout << "\tCV_EVENT_FLAG_LBUTTON" << std::endl;
    }
    if ( flags & CV_EVENT_FLAG_RBUTTON )
    {
        std::cout << "\tCV_EVENT_FLAG_RBUTTON" << std::endl;
    }
    if ( flags & CV_EVENT_FLAG_MBUTTON )
    {
        std::cout << "\tCV_EVENT_FLAG_MBUTTON" << std::endl;
    }
    if ( flags & CV_EVENT_FLAG_CTRLKEY )
    {
        std::cout << "\tCV_EVENT_FLAG_CTRLKEY" << std::endl;
    }
    if ( flags & CV_EVENT_FLAG_SHIFTKEY )
    {
        std::cout << "\tCV_EVENT_FLAG_SHIFTKEY" << std::endl;
    }
    if ( flags & CV_EVENT_FLAG_ALTKEY )
    {
        std::cout << "\tCV_EVENT_FLAG_ALTKEY" << std::endl;
    }
 
}
 
 
/*/////////////////////////////////////
@ function: main
*//////////////////////////////////////
int main()
{
    /// Read image from file
    cv::Mat img = cv::imread( {YOUR_IMAGE_PATH} );
  
    /// if fail to read the image
    if ( img.empty() )
    {
        std::cout << "Error loading the image" << std::endl;
        return -1;
    }
  
    /// Create a window
    cv::namedWindow( "ImageDisplay", 1 );
  
    /// set the callback function for any mouse event
    cv::setMouseCallback( "ImageDisplay", CallBackFunc, NULL );
  
    /// show the image
    cv::imshow( "ImageDisplay", img );
  
    /// Wait until user press some key
    waitKey( 0 );
     
    return 0;
}

Example 2 - FILL DEMO

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/videoio/videoio.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <iostream>
 
using namespace std;
using namespace cv;
 
 
// Global
cv::Mat image0, image, gray, mask;
int ffillMode = 1;
int loDiff = 20, upDiff = 20;
int connectivity = 4;
int isColor = true;
bool useMask = false;
int newMaskVal = 255;
 
 
/*/////////////////////////////////////
@ function: help
*//////////////////////////////////////
static void help()
{
    cout << "\nThis program demonstrated the floodFill() function\n"
            "Call:\n"
            "./ffilldemo [image_name -- Default: ../data/fruits.jpg]\n" << endl;
 
    cout << "Hot keys: \n"
            "\tESC - quit the program\n"
            "\tc - switch color/grayscale mode\n"
            "\tm - switch mask mode\n"
            "\tr - restore the original image\n"
            "\ts - use null-range floodfill\n"
            "\tf - use gradient floodfill with fixed(absolute) range\n"
            "\tg - use gradient floodfill with floating(relative) range\n"
            "\t4 - use 4-connectivity mode\n"
            "\t8 - use 8-connectivity mode\n" << endl;
}
 
 
/*/////////////////////////////////////
@ function: onMouse
*//////////////////////////////////////
static void onMouse( int event, int x, int y, int, void* )
{
    if( event != EVENT_LBUTTONDOWN )
        return;
 
    Point seed = Point(x,y);
    int lo = ffillMode == 0 ? 0 : loDiff;
    int up = ffillMode == 0 ? 0 : upDiff;
    int flags = connectivity + (newMaskVal << 8) +
                (ffillMode == 1 ? FLOODFILL_FIXED_RANGE : 0);
    int b = (unsigned)theRNG() & 255;
    int g = (unsigned)theRNG() & 255;
    int r = (unsigned)theRNG() & 255;
    Rect ccomp;
 
    cv::Scalar newVal = isColor ? cv::Scalar( b, g, r ) : cv::Scalar( r*0.299 + g*0.587 + b*0.114 );
    cv::Mat dst = isColor ? image : gray;
    int area;
 
    if( useMask )
    {
        cv::threshold( mask, mask, 1, 128, THRESH_BINARY );
        area = cv::floodFill( dst, mask, seed, newVal, &ccomp, cv::Scalar( lo, lo, lo ), cv::Scalar( up, up, up ), flags );
        cv::imshow( "mask", mask );
    }
    else
    {
        area = cv::floodFill( dst, seed, newVal, &ccomp, cv::Scalar( lo, lo, lo ), cv::Scalar( up, up, up ), flags );
    }
 
    cv::imshow( "image", dst );
    std::cout << area << " pixels were repainted\n";
}
 
 
 
/*/////////////////////////////////////
@ function: main
*//////////////////////////////////////
int main()
{
    cv::Mat image0 = imread( {YOUR_IMAGE_PATH}, 1 );
 
    if( image0.empty() )
    {
        cout << "Image empty. Usage: ffilldemo <image_name>\n";
        return 0;
    }
 
    help();
 
    image0.copyTo(image);
    cv::cvtColor(image0, gray, COLOR_BGR2GRAY);
    mask.create(image0.rows+2, image0.cols+2, CV_8UC1);
 
    namedWindow( "image", 0 );
    createTrackbar( "lo_diff", "image", &loDiff, 255, 0 );
    createTrackbar( "up_diff", "image", &upDiff, 255, 0 );
 
    setMouseCallback( "image", onMouse, 0 );
 
    for(;;)
    {
        imshow( "image", isColor ? image : gray );
 
        int c = waitKey( 0 );
 
        if( (c & 255) == 27 )
        {
            cout << "Exiting ...\n";
            break;
        }
 
        switch( (char)c )
        {
        case 'c':
            if( isColor )
            {
                std::cout << "Grayscale mode is set\n";
                cv::cvtColor(image0, gray, COLOR_BGR2GRAY);
                mask = Scalar::all(0);
                isColor = false;
            }
            else
            {
                std::cout << "Color mode is set\n";
                image0.copyTo(image);
                mask = Scalar::all(0);
                isColor = true;
            }
            break;
 
        case 'm':
            if( useMask )
            {
                cv::destroyWindow( "mask" );
                useMask = false;
            }
            else
            {
                cv::namedWindow( "mask", 0 );
                mask = Scalar::all( 0 );
                cv::imshow( "mask", mask );
                useMask = true;
            }
            break;
 
        case 'r':
            std::cout << "Original image is restored\n";
            image0.copyTo( image );
            cv::cvtColor( image, gray, COLOR_BGR2GRAY );
            mask = Scalar::all( 0 );
            break;
 
        case 's':
            std::cout << "Simple floodfill mode is set\n";
            ffillMode = 0;
            break;
 
        case 'f':
            std::cout << "Fixed Range floodfill mode is set\n";
            ffillMode = 1;
            break;
 
        case 'g':
            std::cout << "Gradient (floating range) floodfill mode is set\n";
            ffillMode = 2;
            break;
 
        case '4':
            std::cout << "4-connectivity mode is set\n";
            connectivity = 4;
            break;
 
        case '8':
            std::cout << "8-connectivity mode is set\n";
            connectivity = 8;
            break;
        }
    }
     
    return 0;
}

Result

Original	Ffill

Example 3 - ExtractColor

마우스를 클릭한 위치의 컬러 정보를 얻는 예제.

#include "opencv2/highgui/highgui.hpp"
#include <iostream>
 
using namespace std;
using namespace cv;
 
 
/*/////////////////////////////////////
@ function: mouseEvent
*//////////////////////////////////////
void mouseEvent( int evt, int x, int y, int flags, void* param ) 
{                    
    cv::Mat* rgb = (cv::Mat*) param;
    if ( evt == CV_EVENT_LBUTTONDOWN )
    { 
        printf("%d %d: %d, %d, %d\n", 
        x, y, 
        (int)(*rgb).at<Vec3b>(y, x)[0], 
        (int)(*rgb).at<Vec3b>(y, x)[1], 
        (int)(*rgb).at<Vec3b>(y, x)[2]); 
    }         
}
 
 
/*/////////////////////////////////////
@ function: main
*//////////////////////////////////////
int main()
{
    /// Read image from file
    cv::Mat img = cv::imread( {YOUR_IMAGE_PATH} );
  
    /// if fail to read the image
    if ( img.empty() )
    {
        std::cout << "Error loading the image" << std::endl;
        return -1;
    }
  
    /// Create a window
    cv::namedWindow( "My Window", 1 );
  
    /// set the callback function for any mouse event
    cv::setMouseCallback( "My Window", mouseEvent, &img );
  
    /// show the image
    cv::imshow( "My Window", img );
  
    /// Wait until user press some key
    cv::waitKey(0);
     
    return 0;
}