For all the people who've:

1. registered the sizes in their functions.php
2. set them in a callback for after_setup_theme with the add_action function
3. installed Regenerate Thumbnails
4. installed php5_gd and restarted the server

You may have to manually configure the loading of the extension, if it wasn't for you.

First, check if GD is actually enabled as an extension. Run this snippet in a .php file on the browser to find out:

<?php if (extension_loaded('gd')) 
     { 
         echo "gd loaded"; 
     } else { 
         echo "not loaded"; 
} ?>

If it comes up with "not loaded", the solution found was adding the line:

extension=gd.so

to the apache2/php.ini file.

For all the people who've:

1. registered the sizes in their functions.php
2. set them in a callback for after_setup_theme with the add_action function
3. installed Regenerate Thumbnails
4. installed php5_gd and restarted the server

You may have to manually configure the loading of the extension, if it wasn't for you.

First, check if GD is actually enabled as an extension. Run this snippet in a .php file on the browser to find out:

<?php if (extension_loaded('gd')) 
     { 
         echo "gd loaded"; 
     } else { 
         echo "not loaded"; 
} ?>

If it comes up with "not loaded", the solution found was adding the line:

extension=gd.so

to the apache2/php.ini file.

I wanted to put this here since it's the top question for this on stackexchange:

For all the people who've:

1. registered the sizes in their functions.php
2. set them in a callback for after_setup_theme with the add_action function
3. installed Regenerate Thumbnails
4. installed php5_gd and restarted the server

And sizes still aren't hard-cropping....

Check if GD is actually enabled as an extension by running this snippet in a .php file on the browser:

<?php if (extension_loaded('gd')) 
     { 
         echo "gd loaded"; 
     } else { 
         echo "not loaded"; 
} ?>

If it comes up with "not loaded", then try adding the line:

extension=gd.so

to the apache2/php.ini file. That was the end result after trying out all the other solutions online which ended with installing php5-gd: you may have to manually configure the loading of the extension afterwards.

For all the people who've:

1. registered the sizes in their functions.php
2. set them in a callback for after_setup_theme with the add_action function
3. installed Regenerate Thumbnails
4. installed php5_gd and restarted the server

You may have to manually configure the loading of the extension, if it wasn't for you.

First, check if GD is actually enabled as an extension. Run this snippet in a .php file on the browser to find out:

<?php if (extension_loaded('gd')) 
     { 
         echo "gd loaded"; 
     } else { 
         echo "not loaded"; 
} ?>

If it comes up with "not loaded", the solution found was adding the line:

extension=gd.so

to the apache2/php.ini file.