指定区域内图像颜色反转

#include "stdafx.h"
#include <stdio.h>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>

using namespace cv;
using namespace std;

Rect selection;
int select_object;

/* prototype declaration */
void on_mouse(int event, int x, int y, int flags, void* param);

int main(int argc, char *argv[])
{
// (1)load a source image as is
const char *imagename = argc > 1 ? argv[1] : "../image/fruit.png";
Mat src_img = imread(imagename, -1);
if(!src_img.data)
return -1;

// (2)create a window and set the callback function for mouse events
namedWindow("Image", 1);
cvSetMouseCallback("Image", (CvMouseCallback)(&on_mouse), &src_img);

// (3)show the source image with an invert area, and quit when 'esc' pressed
while(1) {
Mat dst_img = src_img.clone();
if(select_object && selection.width > 0 && selection.height > 0) {
Mat roi(dst_img, selection);
bitwise_xor(roi, Scalar::all(255), roi);
}

imshow("Image", dst_img);
int key = waitKey(10);
if((char)key==27)
break;
}

return 0;
}

void on_mouse(int event, int x, int y, int flags, void* param)
{
static Point2i origin;
Mat *img = static_cast<Mat*>(param);

// (4)calculate coordinates of selected area (by Click and Drag)
if(select_object) {
selection.x = CV_IMIN(x, origin.x);
selection.y = CV_IMIN(y, origin.y);
selection.width = selection.x + CV_IABS(x - origin.x);
selection.height = selection.y + CV_IABS(y - origin.y);

selection.x = CV_IMAX(selection.x, 0);
selection.y = CV_IMAX(selection.y, 0);
selection.width = CV_IMIN( selection.width, img->cols );
selection.height = CV_IMIN( selection.height, img->rows );
selection.width -= selection.x;
selection.height -= selection.y;
}

// (5)process a start and a finish selecting events (i.e. button-up and -down)
switch(event) {
case CV_EVENT_LBUTTONDOWN:
origin = Point2i(x,y);
selection = Rect(x, y, 0, 0);
select_object = 1;
break;
case CV_EVENT_LBUTTONUP:
select_object = 0;
break;
}
}