I'm getting some trouble to work with the_post_thumbnail() function. The problem is that I can't resize the image to the siza that I want to. I'm trying to resize a big image to 660px x 330px, but it's not working. I tried:
1) the_post_thumbnail( array( 660, 330 ) );
2) add_image_size( 'slider', 660, 330 );
3) add_image_size( 'slider', 660, 330, true );
Nothing works. Any idea?