PNG Portable Network Graphics

SIGNATURE = bytes.fromhex("89504e470d0a1a0a")
OFFSET = 0

def is_png(path: str) -> bool:
    with open(path, "rb") as f:
        f.seek(OFFSET)
        head = f.read(len(SIGNATURE))
    return head == SIGNATURE

const SIGNATURE = [0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a];
const OFFSET = 0;

// bytes: a Uint8Array / Buffer holding the start of the file
export function isPng(bytes) {
  return SIGNATURE.every((byte, i) => bytes[OFFSET + i] === byte);
}

package fileid

import "bytes"

var ispngSignature = []byte{0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a}

const ispngOffset = 0

func IsPng(b []byte) bool {
	end := ispngOffset + len(ispngSignature)
	if len(b) < end {
		return false
	}
	return bytes.Equal(b[ispngOffset:end], ispngSignature)
}

const SIGNATURE: &[u8] = &[0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a];
const OFFSET: usize = 0;

fn is_png(bytes: &[u8]) -> bool {
    bytes.get(OFFSET..OFFSET + SIGNATURE.len()) == Some(SIGNATURE)
}

<?php
$signature = "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a";
$offset = 0;

function is_png(string $bytes): bool {
    global $signature, $offset;
    return substr($bytes, $offset, strlen($signature)) === $signature;
}