Microsoft Visual Studio C++, OpenCV animation - c++

Question

I have a problem and I am not quite sure how to move past it. I want to create an animation that changes the colour (fluently) of the contour which I have extracted. I assume that all I have to do is use while loop (for animation), and change the value of one of the r, g, b variables (with for loop), but I'm not sure HOW to properly do that.
Thanks in advance!
using namespace cv;
using namespace std;
int main()
{
Mat OurImage, img, bin, anim, gray;
string Destination = "rot.jpg";
OurImage = imread(Destination, CV_LOAD_IMAGE_COLOR);
if(! OurImage.data)
{
printf("No image!");
getchar();
return -1;
}
int r = 0, g = 255, b = 255;
vector<vector<Point>> contours;
vector<Vec4i> hierarchy;
cvtColor(OurImage,gray,CV_RGB2GRAY);
Canny( gray, img, 100, 200,3);
findContours(img,contours,hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE);
Mat drawing = Mat::zeros(img.size(),CV_8UC3);
for(int i = 0; i < contours.size(); i++)
{
Scalar color = Scalar(r, g, b);
drawContours(drawing, contours,i,color,2,8,hierarchy, 0,Point());
}
namedWindow("WINDOW", CV_WINDOW_AUTOSIZE);
while(true)
{
NO IDEA WHAT THE FOR LOOP SHOULD LOOK LIKE HERE
printf(".");
anim = drawing.clone();
r = r+5;
imshow("WINDOW",anim);
if(waitKey(20) == 27)
break;
}
waitKey(0);
}
EDIT
I have managed to make it work from yellow to white ( from 0 to 255), but now I don't know how to make it go back and force the program to do that till I click. Do I use a flag/if? another for?
while(true)
{
for(int i = 0; i < contours.size(); i++)
{
r=r+5;
printf(".");
Scalar color = Scalar(r, g, b);
drawing = drawing.clone();
drawContours(drawing, contours,i,color,2,8,hierarchy, 0,Point());
}
imshow("WINDOW",drawing);
if(waitKey(20) == 27)
break;
}

Answer 1

This code will change continuously the color of the edges from white to yellow, and back.
You can change the animation speed with delay.
Note that you can change olny the edge points using setTo with the edge mask. If you need to draw a thicker edges, you can call drawContours with index -1 to draw all contours, without the for loop.
Keep also in mind that OpenCV Highgui is manly for debugging purposes. Anything more than you program like this one should be done using an appropriate GUI library (like, among others, Qt).
#include <opencv2/opencv.hpp>
#include <vector>
using namespace std;
using namespace cv;
int main()
{
// Yellow image
Mat3b img = imread("path_to_image");
int step = 5; // Color step
int delay = 30; // Animation speed
bool forward = true;
Scalar color(0,255,255);
Mat1b gray;
cvtColor(img, gray, COLOR_BGR2GRAY);
Mat1b edges;
Canny(gray, edges, 400, 200);
vector<vector<Point>> contours;
findContours(edges, contours, RETR_LIST, CHAIN_APPROX_SIMPLE);
Mat3b canvas(img.rows, img.cols, Vec3b(0,0,0));
while (true)
{
imshow("Draw", canvas);
if (waitKey(delay) == 27 /*ESC*/) break;
// Update color
color[0] = color[0] + ((forward) ? step : -step);
// Deal with direction
if (forward && color[0] > 255) {
forward = false;
color[0] = 255;
}
if (!forward && color[0] < 0) {
forward = true;
color[0] = 0;
}
// Update only edge points
//canvas.setTo(color, edges);
// Draw a thick contour
drawContours(canvas, contours, -1, color, 2);
}
return 0;
}