Open a png file and read it's hex values in C

Question

I am attempting to read a file with any filetype ending and determining from it's hex values if it is a PNG file. So far I have tried on two different paths but none are working. - With first I read first 16 characters since first 8 hex values determines if it has the right header. Then I try to seperate it and read is as hex value as it was presented in some other thread here. - The other I just want to read first two values and determine if it is hex value to even see if it's working. It is not. code: ``` int IS_PNG_FILE(char *name) { FILE *dat = fopen (name, "rt"); if (dat == NULL) return 1; int data_point; char buf[16], a[16]; fgets(buf, 16, dat); printf("%s
", buf); int i, b; for (i=0; i<16; i++) { sscanf(&buf[i], "%2x", &b); a[i] = b; i += 2; } printf("%d
", a); fscanf(dat, "%2x", &data_point); printf("%d
", data_point); fclose(dat); return 0; } ```

Accepted Answer

In order to read the binary bytes from the file use `fread`:

The function fread() reads nmemb elements of data, each size bytes long, from the stream pointed to by stream, storing them at the location given by ptr.

something like:

```
unsigned char head[8];

fread(head, sizeof(head), 1, dat);
```

you can check the return value to verify that 8 bytes were actually read.

then compare using memcmp

```
unsigned char signature[8] = {0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A};

if (!memcmp(signature, head, 8))
{
    ...
}
```

Open a png file and read it's hex values in C

Solution

Problem