Mat data access

MatDataAccess.cpp

#include "opencv2/opencv.hpp"

using namespace cv;
using namespace std;

int main(int, char)
{
	namedWindow("img", 1);
	Mat img = imread("anapji.jpg");
	
	if (img.depth() == CV_8U)
		printf("8bit unsigend\n");

	img.

	/*
	cout << img.elemSize() << endl;
	cout << img.channels() << endl;
	cout << img.rows << endl;
	cout << img.step << endl;
	*/

	//using data
	//for (int i = img.rows / 10 * 7; i < img.rows / 10 * 8; i++) {

	//for (int i = 0; i < img.rows ; i++) {

	for (int i = img.rows / 10 * 7; i < img.rows / 10 * 8; i++) {
		for (int j = 0; j < img.cols; j++) {


			unsigned char r, g, b;

			b = img.data[i * img.step + j * img.elemSize() + 0];
			g = img.data[i * img.step + j * img.elemSize() + 1];
			r = img.data[i * img.step + j * img.elemSize() + 2];

			img.data[i * img.step + j * img.elemSize() + 0] = unsigned char(255 - b);
			img.data[i * img.step + j * img.elemSize() + 1] = unsigned char(255 - g);
			img.data[i * img.step + j * img.elemSize() + 2] = unsigned char(255 - r);

		}
	}




	

	//using at
	for (int i = img.rows / 10 * 2; i < img.rows / 10 * 3; ++i)
	{
		for (int j = 0; j < img.cols; ++j)
		{
			//Vec3b means 'uchar 3ch'
			unsigned char b = img.at< cv::Vec3b>(i, j)[0];
			unsigned char g = img.at< cv::Vec3b>(i, j)[1];
			unsigned char r = img.at< cv::Vec3b>(i, j)[2];

			//printf("%d %d %d\n", b, g, r);

			img.at< cv::Vec3b>(i, j)[0] = unsigned char(255 - b); //b
			img.at< cv::Vec3b>(i, j)[1] = unsigned char(255 - g); //g
			img.at< cv::Vec3b>(i, j)[2] = unsigned char(255 - r); //r
		}
	}


	
	//using ptr
	for (int i = img.rows / 10 * 5; i < img.rows / 10 * 6; i++) {

		cv::Vec3b* ptr = img.ptr< cv::Vec3b >(i);

		for (int j = 0; j < img.cols; j++) {

			unsigned char b1 = (ptr[j][0]);
			unsigned char g1 = (ptr[j][1]); //note!!
			unsigned char r1 = (ptr[j][2]);


			cv::Vec3b bgr = ptr[j];
			unsigned char b2 = (bgr[0]);
			unsigned char g2 = (bgr[1]); //note!!
			unsigned char r2 = (bgr[2]);

			

			ptr[j] = cv::Vec3b(255 - b1, 255 - g1, 255 - r1);

		}
	}



	

	//using iteration
	cv::MatIterator_< cv::Vec3b> itd = img.begin< cv::Vec3b>(), itd_end = img.end< cv::Vec3b>();

	for (int i = 0; itd != itd_end; ++itd, ++i) {

		cv::Vec3b bgr = (*itd);

		(*itd)[0] = 255 - bgr[0];
		(*itd)[1] = 255 - bgr[1];
		(*itd)[2] = 255 - bgr[2];
	}

	

	imshow("img", img); //show
	waitKey(0);

	destroyAllWindows();

	return 0;
}