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1.  引言：

C语言把文件看作一个字符（字节）的序列，即由一个个字符（字节）的数据顺序组成。根据数据组织形式，可分为ASCII文件和二进制文件。ASCII文件又称为文本（text）文件，它的每个字节放一个ASCII代码，代表一个字符。二进制文件是把内存中的数据按其在内存中的存储形式原样输出到磁盘上存放。

怎样保存和读取文件中的数据流呢?学会这些I/O函数即可，如下：

2. 代码示例：

该代码以图像数据的保存为例，实践了各种流数据相关函数：

#include "stdio.h"
#include  "opencv2/opencv.hpp"using namespace std;
using namespace cv;int main()
{/*【1】读取一幅图片，转化成灰度图，获取图片数据 */Mat imgBGR = imread("lena.jpg");if (imgBGR.data == NULL){printf("read img error!\n");}int width = imgBGR.cols;int height = imgBGR.rows;Mat imgGray;cvtColor(imgBGR, imgGray, CV_BGR2GRAY);uchar* pData = imgGray.data;/* 【2】fwrite保存图像信息到bat文件 */FILE* fp1 = NULL;fp1 = fopen("imgGrayInfo_fwrite.dat","wb");if (fp1 == NULL){printf("imgGrayInfo.dat not exist!\n");}// [2-1] 保存图像的宽和高fwrite(&width, sizeof(int), 1, fp1);fwrite(&height, sizeof(int), 1, fp1);// [2-2] 按行保存图像数据for (int i = 0; i < height; i ++){fwrite(pData, sizeof(char),width, fp1);fwrite("\n", sizeof(char), 1, fp1);pData += width;}fclose(fp1);/* 【3】fread读取dat文件信息 */int cols = 0, rows = 0;char tmp[2];char imgData[1024];memset(imgData, 0, sizeof(char)*1024);FILE* fp2 = NULL;fp2 = fopen("imgGrayInfo_fwrite.dat", "rb");if (NULL == fp2){printf("the dat that you want to read is not exsit!\n");}// [3-1] 读取图像的宽和高fread(&cols, sizeof(int), 1, fp2);fread(&rows, sizeof(int), 1, fp2);printf("rows:%d\t cols：%d\t", rows, cols);// [3-2] 读取图像数据for (int i = 0; i < height; i++){fwrite(imgData, sizeof(char), width, fp2);fwrite(tmp, sizeof(char), 1, fp2);}fclose(fp2);/*【4】fprintf 保存图像到txt */pData = imgGray.data;FILE*  fp3 = NULL;fp3 = fopen("imgGrayInfo_fprintf.txt", "w+");if (!fp3){printf("the txt file that you want to write is not exist!\n");}// [4-1] 保存图像的宽和高fprintf(fp3,"%d%c", width,'\t');fprintf(fp3,"%d%c",height,'\n');// [4-2] 以整型方式保存图像数据for (int i = 0; i < 1; i++)  //保存一行{for (int j = 0; j < width; j++){fprintf(fp3, "%d%c", *pData, '\n');pData++;}fprintf(fp3, "%c", pData,'\n');}fclose(fp3);/* 【5】fscanf读取txt数据*/int ntmp = 0;FILE* fp4 = NULL;fp4 = fopen("imgGrayInfo_fprintf.txt", "r");if (!fp4){printf("the txt file that you want to read is not exist!\n");}fscanf(fp4, "%d", &cols);fscanf(fp4, "%d", &rows);int k = 0;while (!feof(fp4)){fscanf(fp4, "%d", &ntmp);printf("%d\n", ntmp);}fclose(fp4);return 0;
}