opencv图像操作——at方法使用

opencv图像操作——at方法使用

1. 图像的读写
2. 读写像素
3. 修改像素值

图像的读写

imread 可以指定加载灰度图像或者是RGB图像
imwrite 保存图像文件，类型由扩展名决定

读写像素

1. 读写一个灰度图像（GRAY）像素点的像素值 ：Scalar intensity = Mat.at<uchar>(y,x)或者Scalar intensity = Mat.at<uchar>(Point(x,y))2. 都一个RGB像素点的像素值：Vec3f intensity  = Mat.at<Vec3f>(y,x)float blue = intensity.val[0]   //获得蓝色通道的像素值float green = intensity.val[1]   //获得蓝色通道的像素值float red = intensity.val[2]      //获得蓝色通道的像素值整型：int b = srcImage.at<Vec3b>(row, col)[0];  //获取像素值b int g = srcImage.at<Vec3b>(row, col)[1];  //获取像素值gint r = srcImage.at<Vec3b>(row, col)[2];  //获取像素值r

修改像素值

int gray = gray_src.at<uchar>(row,col);    //获取像素值
gray_src.at<uchar>(row,col) = 255-gray; //像素值取反赋值

例子

• 灰度图像的像素取反操作：

#include<opencv2/opencv.hpp>
#include<iostream>using namespace cv;int main(int argc, char** argv) {Mat srcImage = imread("E:/image/6.jpg");Mat gray_src;if (!srcImage.data) {printf("没有找到图片");return -1;}namedWindow("input image",WINDOW_AUTOSIZE);imshow("input image", srcImage);cvtColor(srcImage, gray_src, COLOR_BGR2GRAY);namedWindow("input gray", WINDOW_AUTOSIZE);imshow("input gray", gray_src);int heigth = ws;int width = ls;for (int row = 0; row < heigth; row++) {for (int col = 0; col < width; col++) {int gray = gray_src.at<uchar>(row,col);    //获取像素值gray_src.at<uchar>(row,col) = 255-gray; //像素值取反赋值}}namedWindow("取反操作",WINDOW_AUTOSIZE);![imshow("取反操作", gray_src);waitKey(0);return 0;
}

效果图：

• 对彩色像素值进行操作：

#include<opencv2/opencv.hpp>
#include<iostream>using namespace cv;int main(int argc, char** argv) {Mat srcImage = imread("E:/image/6.jpg");if (!srcImage.data) {printf("没有找到图片");return -1;}namedWindow("input image",WINDOW_AUTOSIZE);imshow("input image", srcImage);Mat ate(srcImage.size(), pe());int heigth = ws;int width = ls;int nc = srcImage.channels();for (int row = 0; row < heigth; row++) {for (int col = 0; col < width; col++) {if(nc==1){int gray = srcImage.at<uchar>(row, col);    //获取像素值dst.at<uchar>(row, col) = 255 - gray; //像素值取反赋值}else if (nc == 3) {int b = srcImage.at<Vec3b>(row, col)[0];  //获取像素值b int g = srcImage.at<Vec3b>(row, col)[1];  //获取像素值gint r = srcImage.at<Vec3b>(row, col)[2];  //获取像素值rdst.at<Vec3b>(row, col)[0] = 255 - b;dst.at<Vec3b>(row, col)[1] = 255 - g;dst.at<Vec3b>(row, col)[2] = 255 - r;}}}namedWindow("取反操作",WINDOW_AUTOSIZE);imshow("取反操作", dst);waitKey(0);return 0;
}

效果图：

• opencv提供的api方法bitwise_not:

#include<opencv2/opencv.hpp>
#include<iostream>using namespace cv;int main(int argc, char** argv) {Mat srcImage = imread("E:/image/6.jpg");if (!srcImage.data) {printf("没有找到图片");return -1;}namedWindow("input image",WINDOW_AUTOSIZE);imshow("input image", srcImage);Mat ate(srcImage.size(), pe());bitwise_not(srcImage, dst);namedWindow("取反操作",WINDOW_AUTOSIZE);imshow("取反操作", dst);waitKey(0);return 0;
}

效果图：