X Window Dump (Legacy MIME Alias)

import magic
# Libmagic will identify XWD files based on their structural header signature
print(magic.from_file('screenshot.xwd', mime=True)) # Outputs 'image/x-xwd'

const fs = require('fs');
// Inspecting the first 8 bytes for header size 100 (0x64) and version 7 (0x07)
const buffer = Buffer.alloc(8);
const fd = fs.openSync('screenshot.xwd', 'r');
fs.readSync(fd, buffer, 0, 8, 0);
fs.closeSync(fd);
const headerSize = buffer.readUInt32BE(0);
const version = buffer.readUInt32BE(4);
const isXWD = headerSize === 100 && version === 7;
console.log('Is X Window Dump:', isXWD);

import (
    "encoding/binary"
    "os"
)
// Checking the header size and version manually in Go:
// file, _ := os.Open("screenshot.xwd")
// buf := make([]byte, 8)
// file.Read(buf)
// headerSize := binary.BigEndian.Uint32(buf[0:4])
// version := binary.BigEndian.Uint32(buf[4:8])
// isXWD := headerSize == 100 && version == 7

// Normalizing legacy MIME types during file uploads
$mime = $_FILES['upload']['type'];
if ($mime === 'image/x-xwindowdump') {
    $mime = 'image/x-xwd';
}
echo $mime;