<?php
/*
 * Resize images dynamically using wp built in functions
 * Victor Teixeira
 */
function vt_resize( $attach_id = null, $img_url = null, $width, $height, $crop = false ) {

	// this is an attachment, so we have the ID
	if ( $attach_id ) {
	
		$image_src = wp_get_attachment_image_src( $attach_id, 'full' );
		$file_path = get_attached_file( $attach_id );
	
	// this is not an attachment, let's use the image url
	} else if ( $img_url ) {

		//$uploads = wp_upload_dir();
		//$file_path = str_replace($uploads["url"],$uploads["path"],$img_url );
		
		$file_path = parse_url( $img_url );
		$file_path = ltrim( $file_path['path'], '/' );
		$file_path = rtrim( ABSPATH, '/' ).$file_path['path'];
		
		$orig_size = getimagesize( $file_path );
		
		$image_src[0] = $img_url;
		$image_src[1] = $orig_size[0];
		$image_src[2] = $orig_size[1];
	}
	
	$file_info = pathinfo( $file_path );
	$extension = '.'. $file_info['extension'];

	// the image path without the extension
	$no_ext_path = $file_info['dirname'].'/'.$file_info['filename'];

	$cropped_img_path = $no_ext_path.'-'.$width.'x'.$height.$extension;

	// checking if the file size is larger than the target size
	// if it is smaller or the same size, stop right here and return
	if ( $image_src[1] > $width || $image_src[2] > $height ) {

		// the file is larger, check if the resized version already exists (for crop = true but will also work for crop = false if the sizes match)
		if ( file_exists( $cropped_img_path ) ) {

			$cropped_img_url = str_replace( basename( $image_src[0] ), basename( $cropped_img_path ), $image_src[0] );
			
			$vt_image = array (
				'url' => $cropped_img_url,
				'width' => $width,
				'height' => $height
			);
			
			return $vt_image;
		}

		// crop = false
		if ( $crop == false ) {
		
			// calculate the size proportionaly
			$proportional_size = wp_constrain_dimensions( $image_src[1], $image_src[2], $width, $height );
			$resized_img_path = $no_ext_path.'-'.$proportional_size[0].'x'.$proportional_size[1].$extension;			

			// checking if the file already exists
			if ( file_exists( $resized_img_path ) ) {
			
				$resized_img_url = str_replace( basename( $image_src[0] ), basename( $resized_img_path ), $image_src[0] );

				$vt_image = array (
					'url' => $resized_img_url,
					'width' => $new_img_size[0],
					'height' => $new_img_size[1]
				);
				
				return $vt_image;
			}
		}

		// no cached files - let's finally resize it
		$new_img_path = wp_get_image_editor( $file_path, $width, $height, $crop );
		$new_img_size = getimagesize( $new_img_path );
		$new_img = str_replace( basename( $image_src[0] ), basename( $new_img_path ), $image_src[0] );

		// resized output
		$vt_image = array (
			'url' => $new_img,
			'width' => $new_img_size[0],
			'height' => $new_img_size[1]
		);
		
		return $vt_image;
	}

	// default output - without resizing
	$vt_image = array (
		'url' => $image_src[0],
		'width' => $image_src[1],
		'height' => $image_src[2]
	);
	
	return $vt_image;
}
?>