从buffer快速保存pgm图片，不借助第三方库

#include <iostream>

#include <stdlib.h>

#include <list>

#include <opencv2/core/core.hpp>

#include <opencv2/highgui/highgui.hpp>

#include <opencv2/opencv.hpp>

using namespacestd;

using namespacecv;

int pgm_encode(constunsigned char *image,int width, int height,int color_byte, unsignedchar *pgm_buf, int *buf_size);

int main(int argc,const char * argv[]) {

    // insert code here...

    std::cout <<"Hello, World!\n";

    char filename[256] ="testImages/1.bmp";

    Mat testImage =imread(filename,0);

    if (testImage.data ==NULL ) {

        cout<<"load image error"<<endl;

        exit(1);

    }

    

    FILE* pfile =fopen("test.pbm","wb");

    int w = testImage.cols;

    int h = testImage.rows;

    fprintf(pfile,"P%d\n%d %d\n255\n", 5, w, h);

    fwrite(testImage.data,1, w*h, pfile);

    

    

    return0;

}

pgm相关资料：https://zh.wikipedia.org/wiki/PBM%E6%A0%BC%E5%BC%8F