我需要使用缓冲区以c语言复制位图图像文件

Question

i have to copy a bitmap image file using a buffer. here is an example of what i need to do. i have to read different parts of a bitmap into the buffer first at once and then write it to the target file. when i read different parts into the buffer , the previous string gets overwritten and the last string that is read is only written. i dont want to use read and write function for every part that has to be written. please help me with the code.

#include <conio.h>
#include <stdio.h>
#include <stdlib.h>

void fskip(FILE *fp, int num_bytes) {
  int i;
  for (i = 0; i < num_bytes; i++)
    fgetc(fp);
}

int main() {
  FILE *fp, *fp1;

  fp = fopen("c:\\users\\tapan\\desktop\\splash.bmp", "rb");
  fp1 = fopen("c:\\users\\tapan\\desktop\\splash2.bmp", "wb");

  int *j;
  j = (int *)malloc(3000);

  int k = 223121;
  int *i = &k;

  fread(j, 2, 1, fp);

  fread(j, 10, 1, fp);
  fwrite(j, 12, 1, fp1);

  fclose(fp1);
  fclose(fp);

  getch();
}

Answer 1

First of all, I will try to address your specific question and avoid any comments about other things in the code.

It looks like the fread() and fwrite() statements are not correct. The following code might be more exact.

   int main() {
     FILE *fp, *fp1;

     fp = fopen("c:\\users\\tapan\\desktop\\splash.bmp", "rb");
     fp1 = fopen("c:\\users\\tapan\\desktop\\splash2.bmp", "wb");

     int *j;
     j = (int *) malloc(3000);

     int k = 223121;
     int *i = &k;

     // read 2 items of sizeof(int) into j from fp
     fread(j, sizeof(int), 2, fp);

     // read 10 items of sizeof(int) into j + 2 from fp
     fread(j+2, sizeof(int), 10, fp);

     // write 12 items of sizeof(int) from j to fp1
     fwrite(j, sizeof(int), 12, fp1);

     fclose(fp1);
     fclose(fp);

     getch();
   }
   // Note. The above code has NOT been tested, it is thrown-up here for discussion.

Format of fread() and fwrite() is per K&R, second edition, page 247.