@ functions.php
add_theme_support(‘post-thumbnails’)
add_image_size(‘prod-thumb’, 353, 235, true);
the_post_thumbnail
get_the_post_thumbnail
echo get_the_post_thumbnail($post->ID, "medium");
wp_get_attachment_image
wp_get_attachment_image_src
$thumb = wp_get_attachment_image_src(get_post_thumbnail_id($post->ID), "medium");
<img src="<?php echo $thumb[0] ?>" alt="" width="<?php echo $thumb[1] ?>" height="<?php echo $thumb[2] ?>" />
thumbnail – 150x150px
medium – 300x300px
large – 1024x1024px
full – original