You can use the native WordPress image_resize function to scale up images. WordPress provides a hook called “image_resize_dimensions” which you can use to overwrite the default cropping settings. Here is a modified function which will support scaling up:
function image_crop_dimensions($default, $orig_w, $orig_h, $new_w, $new_h, $crop){
if ( !$crop ) return null; // let the wordpress default function handle this
$aspect_ratio = $orig_w / $orig_h;
$size_ratio = max($new_w / $orig_w, $new_h / $orig_h);
$crop_w = round($new_w / $size_ratio);
$crop_h = round($new_h / $size_ratio);
$s_x = floor( ($orig_w - $crop_w) / 2 );
$s_y = floor( ($orig_h - $crop_h) / 2 );
return array( 0, 0, (int) $s_x, (int) $s_y, (int) $new_w, (int) $new_h, (int) $crop_w, (int) $crop_h );
}
Now hook this function like so:
add_filter('image_resize_dimensions', 'image_crop_dimensions', 10, 6);
Once thats done, you can use the image_resize function to scale images up or down as required.
$cropped_image = image_resize($image_filepath, $width, $height, true);