OpenCV学习笔记5——core组件访问图像像素

#include<opencv2/core/core.hpp>
#include<opencv2/highgui/highgui.hpp>
#include<iostream>
using namespace std;
using namespace cv;
//指针访问像素
void colorReduce1(Mat &dstImage, Mat &outputImage, int div)
{
	outputImage = dstImage.clone();//复制实参到临时变量
	int rowNumber = outputImage.rows;//行数
	//列数*通道数=每一行元素个数，灰度图通道数为1，彩色图为3
	int colNumber = outputImage.cols*outputImage.channels();
	for (int i = 0; i < rowNumber; i++)
	{
		uchar *data = outputImage.ptr<uchar>(i);//获取第i行首地址
		for (int j = 0; j < colNumber; j++)
		{
			//处理每个像素
			data[j] = data[j] / div * div + div / 2;
		}
	}
}

//迭代器访问像素
void colorReduce2(Mat &dstImage, Mat &outputImage, int div)
{
	outputImage = dstImage.clone();//复制实参到临时变量
	Mat_<Vec3b>::iterator it = outputImage.begin<Vec3b>();
	Mat_<Vec3b>::iterator itend = outputImage.end<Vec3b>();
	
	//对于彩色图像像素
	for (; it != itend; it++)
	{
		//开始处理每个像素
		(*it)[0] = (*it)[0] / div * div + div / 2;
		(*it)[1] = (*it)[1] / div * div + div / 2;
		(*it)[2] = (*it)[2] / div * div + div / 2;
	}
}

//动态地址计算
void colorReduce3(Mat &dstImage, Mat &outputImage, int div)
{
	outputImage = dstImage.clone();//复制实参到临时变量
	int rowNumber = outputImage.rows;//行数
									 //列数*通道数=每一行元素个数，灰度图通道数为1，彩色图为3
	int colNumber = outputImage.cols*outputImage.channels();
	for (int i = 0; i < rowNumber; i++)
	{
		for (int j = 0; j < colNumber; j++)
		{
			//处理每个像素
			outputImage.at<Vec3b>(i, j)[0] = outputImage.at<Vec3b>(i, j)[0] / div * div + div / 2;
			outputImage.at<Vec3b>(i, j)[1] = outputImage.at<Vec3b>(i, j)[1] / div * div + div / 2;
			outputImage.at<Vec3b>(i, j)[2] = outputImage.at<Vec3b>(i, j)[2] / div * div + div / 2;
		}
	}
}

int main()
{
	//原始图像
	Mat srcImage = imread("lena.jpg");
	imshow("原始图像", srcImage);
	//创建效果图
	Mat dstImage;
	//效果图的大小、类型与原图相同
	dstImage.create(srcImage.rows, srcImage.cols, srcImage.type());

	//记录起始时间
	double time0 = static_cast<double>(getTickCount());
	colorReduce1(srcImage, dstImage, 32);
	time0 = ((double)getTickCount() - time0) / getTickFrequency();
	cout << "指针访问像素运行时间：" << time0 << "秒\n";
	imshow("效果图", dstImage);
	waitKey(0);
}

运行结果：

可以看出图像压缩之后变模糊了。