Photon

Photon works for images inside post content, but doesn’t for Thumbails on home page (front page).
this is how my function.php or index.php.
what should I change this?

Theme Functions (functions.php)

}

if ( function_exists( 'add_theme_support' ) ) { // Added in 2.9
	add_theme_support( 'post-thumbnails' );
	set_post_thumbnail_size( 50, 50, true ); // Normal post thumbnails
	add_image_size( 'single-post-thumbnail', 400, 9999 ); // Permalink thumbnail size

}

// retreives image from the post
function getImage($num) {
global $more;
$more = 1;
$content = get_the_content();
$count = substr_count($content, '<img');
$start = 0;
for($i=1;$i<=$count;$i++) {
$imgBeg = strpos($content, '<img', $start);
$post = substr($content, $imgBeg);
$imgEnd = strpos($post, '>');
$postOutput = substr($post, 0, $imgEnd+1);
$image[$i] = $postOutput;
$start=$imgEnd+1;  

$cleanF = strpos($image[$num],'src="')+5;
$cleanB = strpos($image[$num],'"',$cleanF)-$cleanF;
$imgThumb = substr($image[$num],$cleanF,$cleanB);

}
if(stristr($image[$num],'<img')) { echo $imgThumb; }
$more = 0;
}
//retreive image ends

Main Index Template (index.php)

<div class="thumb">
				<a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>">

<?php //$thumb = thman_getcustomfield('thumb',get_the_ID()); if(!empty($thumb)) : ?>
   <?php
    $thumb_url = get_post_meta($post->ID , 'url_thumb', 'true' );
    if($thumb_url!=""){ ?>
	<img src="<?php echo $thumb_url;?>" class="url_thumb" alt="<?php the_title_attribute(); ?>" />
    <?php }
    else { ?>
	<img src="<?php getImage('1'); ?>">
    <?php } ?>

https://wordpress.org/plugins/jetpack/