Adding custom image size for WordPress media Library

To add new custom image size for WordPress media gallery, we can use add_image_size() function.

<?php add_image_size( $name, $width, $height, $crop ); ?>

Example code in theme’s functions.php file

add_image_size( 'category-thumb', 300,160 ); // 300 pixels wide and 160 pixels height - resized
add_image_size( 'homepage-thumb', 220, 180, true ); // 220 pixels wide and 180 pixels height - cropped

Different crop modes

1. Set the image size by resizing the image proportionally (without distorting it):

    add_image_size( 'custom-size', 220, 180 ); // 220 pixels wide by 180 pixels tall, soft proportional crop mode
   

2. Set the image size by cropping the image (not showing part of it):

    add_image_size( 'custom-size', 220, 180, true ); // 220 pixels wide by 180 pixels tall, hard crop mode
   

3. Set the image size by cropping the image and defining a crop position:

    add_image_size( 'custom-size', 220, 220, array( 'left', 'top' ) ); // Hard crop left top
   

Using the New Image Sizes in WordPress

1. For Featured Images

    <?php 
    if ( has_post_thumbnail() ) { 
     the_post_thumbnail( 'your-custom-size-name' ); 
    }
    ?>
   

2. For General Media (PHP/Templates)

    <?php echo wp_get_attachment_image( $post-id, 'your-custom-size-name' ); ?>