<?php
$orig = imagecreatefrompng('04_15-51-30_LLw4sOTM2a.png');

$new = imagecreatetruecolor(854, 480);

for ($i = 0; $i < 427; $i++) {
    imagecopy($new, $orig, $i*2, 0, 0, $i*480, 2, 480);
}

header('Content-type: image/png');
imagepng($new);
imagedestroy($new);
?>