Display actual file size

Hi,

I’m using Toolbox theme, there are codes:

<?php

$images = get_children( array( 'post_parent' => $post->ID, 'post_type' => 'attachment', 'post_mime_type' => 'image', 'orderby' => 'menu_order', 'order' => 'ASC' ) );
	if ( $images ) :
	$total_images = count( $images );
	$image = array_shift( $images );
	$image_img_tag = wp_get_attachment_image( $image->ID, 'large' );

?>

which display the image in post, but if the image long size is 1024 px, it’s only display 640 px, example:

<a href="#"><img width="640" height="401" src="https://img.jpg" class="attachment-large" alt="img033" title="img033" /></a>

Media Settings was set “Large size” to 1204px both max Width and Height.

Can somebody help me to display full 1024px, please?
Thanks,