OpenCV parallel_for_() example.

parallel_for_example.cpp

/*
 * parallel_for_() example. 
 * Paints 8 stripes to different colors in a 80x80 image in parallel.
 * @OpenCVTip on Twitter
**/

#include <opencv2/opencv.hpp>

using namespace cv;

class RandomFillBody : public ParallelLoopBody
{
	Mat3b img;

public:
	RandomFillBody(Mat3b& img) : img(img)
	{ }

	void operator()(const Range& range) const override
	{
		theRNG().state = getTickCount();
		Vec3b color{ theRNG(), theRNG(), theRNG() };

		for (int i = range.start; i < range.end; ++i)
		{
			int x = i % 8, y = i / 8;
			img(Range{ y * 10, (y + 1) * 10 }, Range{ x * 10, (x + 1) * 10 }) = color;
		}
	}
};

int main()
{
	Mat3b img = Mat3b::zeros(80,80);

	parallel_for_(Range{ 0, 64 }, RandomFillBody{ img }, 8);

	imshow("img", img);
	waitKey();
}