1. I added below code in theme's function.php

add_theme_support( 'post-thumbnails' );
add_image_size( 'thumb-small', 200, 150, true );

and <?php the_post_thumbnail('thumb-small'); ?> this in theme's file.

  1. I tried this also in function.php

function add_custom_sizes() {
add_image_size( 'idea-thumb', 146, 141, true ); }


<?php the_post_thumbnail('idea-thumb'); ?> this in theme's file.

  1. the_post_thumbnail( array(100, 100) ); // Other resolutions

But above three condition are not working.

<?php the_post_thumbnail('thumbnail'); ?> //this is working with 150 * 150px as default size.

what i had done mistake.

  • 2
    old existing images will not resize automatically with newly defined image size. You will have to regenerate them again. Use Regenerate Thumbnails plugin to generate thumbnails of all defined sizes.
    – Robert hue
    Nov 8, 2014 at 8:35

1 Answer 1


I Used Regenerate Thumbnails plugin to generate thumbnails

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