CS50 Retrieving blank images when writing program to recover jpgs - c

Question

I am having trouble identifying why I am getting blank images when recovering jps for an assignment in CS50. I read the entire file, write whenever the start of a jpg file is found, and close whenever the end of a jpg file is found. I create the total of 50 images, but all of them are blank. Could someone help push me in the right direction?
This is my code:
const int BLOCK = 512;
uint8_t buffer[BLOCK];
char filename[50][8] = { };
int counter = 0;
while (fread(buffer, BLOCK, 1, input) == 1)
{
sprintf(&filename[counter][0], "%03i.jpg", counter);
FILE *img = fopen(&filename[counter][0], "w");
if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer [2] == 0xff && (buffer[3] & 0xf0) == 0xe0)
{
if ((buffer[511] & 0xf0) != 0xe0)
{
fwrite(buffer, BLOCK, 1, img);
counter++;
}
else
{
fclose(img);
}
}
}
I made the update here:
while (fread(buffer, BLOCK, 1, input) == 1)
{
sprintf(filename, "%03i.jpg", counter);
FILE *img = fopen(filename, "w");
if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer [2] == 0xff && (buffer[3] & 0xf0) == 0xe0)
{
if ((buffer[511] & 0xf0) != 0xe0)
{
fwrite(buffer, BLOCK, 1, img);
}
else
{
fclose(img);
counter++;
}
}
}

Answer 1

This question is now solved. My whole logic was flawed and I wasnt writing anything, I was just opening files. Bellow is my reworked code, its funny how overnight everything just clicked and was able to write it in like 10 minutes!
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
const int BLOCK = 512;
int main(int argc, char *argv[])
{
if (argc != 2)
{
printf("Usage: ./recover card.raw\n");
return 1;
}
FILE *input = fopen(argv[1], "r");
if (input == NULL)
{
printf("Could not open file.\n");
return 1;
}
uint8_t buffer[BLOCK];
char filename[8] = { };
int counter = 0;
FILE *img;
while (fread(buffer, BLOCK, 1, input) == 1)
{
if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer [2] == 0xff && (buffer[3] & 0xf0) == 0xe0)
{
sprintf(filename, "%03i.jpg", counter);
img = fopen(filename, "w");
if (counter == 0)
{
fwrite(buffer, BLOCK, 1, img);
counter++;
}
else
{
fclose(img);
img = fopen(filename, "w");
fwrite(buffer, BLOCK, 1, img);
counter++;
}
}
else if (counter != 0)
{
fwrite(buffer, BLOCK, 1, img);
}
}
fclose(input);
fclose(img);
}