Create missing image size

gistfile1.txt

function thz_create_missing_attachment_size( $attachment_id = false , $handle = false ){

	if( !$handle ){
		return wp_get_attachment_url( $attachment_id );	
	}
	
    global $_wp_additional_image_sizes;

    $default_image_sizes = get_intermediate_image_sizes();

    foreach ( $default_image_sizes as $size ) {
        $image_sizes[ $size ][ 'width' ] = intval( get_option( "{$size}_size_w" ) );
        $image_sizes[ $size ][ 'height' ] = intval( get_option( "{$size}_size_h" ) );
        $image_sizes[ $size ][ 'crop' ] = get_option( "{$size}_crop" ) ? get_option( "{$size}_crop" ) : false;
    }

    if ( isset( $_wp_additional_image_sizes ) && count( $_wp_additional_image_sizes ) ) {
        $image_sizes = array_merge( $image_sizes, $_wp_additional_image_sizes );
    }

	if( isset( $image_sizes[$handle] ) ) {
		
		$file_path 	= get_attached_file( $attachment_id );
		$editor		= wp_get_image_editor( $file_path );
		
		if ( ! is_wp_error( $editor ) ) {
			
			$meta 			= wp_get_attachment_metadata($attachment_id);
			$info 			= pathinfo( $file_path );
			$dir  			= $info['dirname'];
			$ext  			= ( isset( $info['extension'] ) ) ? $info['extension'] : 'jpg';
			$name 			= wp_basename( $file_path, ".$ext" );
			$name 			= preg_replace( '/(.+)(\-\d+x\d+)$/', '$1', $name );
			
			$width			= $image_sizes[$handle]['width'];
			$height			= $image_sizes[$handle]['height'];
			$crop			= $image_sizes[$handle]['crop'];
			
			$size         	= $editor->get_size();
			$orig_width   	= $size['width'];
			$orig_height  	= $size['height'];
			
			if ( ! $height && $width ) {
				$height = round( ( $orig_height * $width ) / $orig_width );
			} elseif ( ! $width && $height ) {
				$width = round( ( $orig_width * $height ) / $orig_height );
			}
			
			$suffix 				= "{$width}x{$height}";
			$new_img				= "{$dir}/{$name}-{$suffix}.{$ext}";
			
			$meta['sizes'][$handle]	= array(
			
				'file' => "{$name}-{$suffix}.{$ext}",
				'width' => $width,
				'height' => $height,
				'mime-type' => "image/{$ext}"
			
			);
			
			if ( ! file_exists( $new_img ) && $editor->resize( $width, $height, $crop ) && $editor->save($new_img) ) {
				
				wp_update_attachment_metadata( $attachment_id, $meta );
				$image = wp_get_attachment_image_src($attachment_id , $handle);
				
				if( $image && isset($image[0]) ){
					
					return $image[0];
				}				
			}
		
		}
	
	}

	return wp_get_attachment_url( $attachment_id );

}