PHP - Script using imagepng won't save file and then display it - php

Question

I'm trying to load an image, edit it, save it and then display it from a script that is called within IMG tags. The script works if I want to just display the image and it does save the image. But it won't save it and then display it. Does anyone know what I'm doing wrong? Any help would be greatly appreciated.
<?php
header('Content-Type: image/png');
$file_location = "test.png";
if (file_exists($file_location)) {
$img_display = #imagecreatefrompng($file_location);
// This section of code removed as doesn't affect result
imagepng($img_display, $file_location);
chmod($file_location, 0777);
imagepng($img_display);
imagedestroy($img_display);
}
?>

Answer 1

Try this and checks if your folder has permission to save the image. chmod 777 on it for sure.
<?php
header('Content-Type: image/png');
$file_location = "test.png";
if (file_exists($file_location)) {
$img_display = imagecreatefrompng($file_location); // Create PNG image
$filename = $file_location + time(); // Change the original name
imagepng($img_display, $filename); // Saves it with another name
imagepng($filename); // Sends it to the browser
imagedestroy($img_display); // Destroy the first image
imagedestroy($filename); // Destroy the second image
}

Answer 2

Try this:
ob_start();
imagepng($img_display);
$contents = ob_get_clean();
file_put_contents($file_location, $contents);
echo $contents;
imagedestroy($img_display);