OpenCV3添加滑动条和鼠标事件到图形界面

鼠标事件和滑动条控制在计算机视觉和OpenCV中非常有用，使用这些控件，用户可以直接与图形界面交互，改变输入图像或者变量的属性值。

/*
    In this section, we are going to introduce you to the concepts of adding slider and
mouse events for basic interactions. To understand this correctly, we will create a small
project, where we paint green circles in the image using the mouse events and blur the 
image with slider.
*/
#include <opencv2/core.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>
using namespace cv;

// Create a variable to save the position value in track
int blurAmount = 15;

// Trackbar call back function
static void onChange(int pos, void* userInput);

// Mouse callback
static void onMouse(int event, int x, int y, int, void* userInput);

int main(int argc, const char** argv)
{
    // Read images
    Mat boy = imread("../images/eating.jpg");

    // Create windows
    namedWindow("Boy");

    // Create a trackbar
    createTrackbar("Boy", "Boy", &blurAmount, 30, onChange, &boy);

    setMouseCallback("Boy", onMouse, &boy);

    // Call to onChange to init
    onChange(blurAmount, &boy);

    // wait app for a key to exit
    waitKey(0);

    // Destroy the windows
    destroyWindow("Boy");

    return 0;
}

// Trackbar call back function
static void onChange(int pos, void* userInput)
{
    if (pos <= 0) return;
    // Aux variable for result
    Mat imgBlur;

    // Get the pointer input image
    Mat* image = (Mat*)userInput;

    // Apply a blur filter
    blur(*image, imgBlur, Size(pos, pos));

    // Show the result
    imshow("Boy", imgBlur);
}

// Mouse callback
static void onMouse(int event, int x, int y, int, void* userInput)
{
    if (event != EVENT_LBUTTONDOWN) return;

    // Get the pointer input image
    Mat *image = (Mat*)userInput;

    // Draw circle
    circle(*image, Point(x, y), 10, Scalar(0, 255, 0), 3);

    // Call onChange to get blurred image
    onChange(blurAmount, image);
}

程序运行效果如下：