c - Editing an image in ppm format -

i'm trying edit image multiplying red component of each pixel 10 , leaving other components (green , blue) untouched. i'm not sure how i'm supposed edit pixels 1 one. have far. think there wrong ppm header well. there way make ppm header without specifying bounds conforms image putting in?

#include <stdlib.h> #include <stdio.h> #define picture_file 1 #define min_args 2 #define h 768 #define w 1024  void solve(file *in_picture, file *out_picture) {     printf("p3  1024 768 255\n");     double r, g, b, row, col;     int ret = fscanf(in_picture, "%lf %lf %lf ", &r, &g, &b);     while(ret != eof)     {         for(row=1; row <= h; row++)          {             for(col=1; col <= w; col++)             {                 fprintf(out_picture, "%lf %lf %lf ", r*10 , g, b);             }         ret = fscanf(in_picture, "%lf %lf %lf ", &r, &g, &b);         }     } }  file *open_file(const char name[], const char mode[]) {     file *file = fopen(name, mode);     if(file == null)     {         perror(name);     exit(1);     }     return file; }  void check_args(int argc, char *argv[]) {     if(argc < min_args)     {         fprintf(stderr, "%s: not enough arguments \n", argv[0]);     exit(1);     } }  int main(int argc, char *argv[]) {     check_args(argc, argv);     file *in_picture = open_file(argv[picture_file], "r");     file *out_picture = open_file("hidden.ppm", "w");      solve(in_picture, out_picture);     fclose(in_picture);     fclose(out_picture);  }