RealNetworks RealPix

import magic
# Libmagic will identify this as an XML or plain text document, not an image.
print(magic.from_file('slideshow.rp', mime=True)) # Outputs 'text/xml' or 'text/plain'

const fs = require('fs');
// Manually detecting the RealPix IMFL root tag
const buffer = Buffer.alloc(5);
const fd = fs.openSync('slideshow.rp', 'r');
fs.readSync(fd, buffer, 0, 5, 0);
fs.closeSync(fd);
const isRealPix = buffer.toString('ascii').toLowerCase() === '<imfl';
console.log('Is RealPix:', isRealPix);

import (
    "bytes"
    "net/http"
)
// http.DetectContentType will detect it as "text/xml; charset=utf-8" if valid XML.
// To explicitly identify RealPix, check the prefix:
// isRealPix := bytes.HasPrefix(bytes.ToLower(buf), []byte("<imfl"))

$mime = mime_content_type('slideshow.rp');
echo $mime; // Standard setups will resolve this to 'text/plain' or 'text/xml'