Wordpress plugin for [image id="123" width="300" align="left"]

wp_image_shortcode.php

<?php
/*
Plugin Name: Image Shortcode
Description: Insert an image by id. This plugin automatically fetches title, size and embedded image.
Version:     1.1
Plugin URI:  https://gist.github.com/jojonas/f6f9590a596645124cb8
Author:      Jonas Lieb
Author URI:  http://www.jonaslieb.com
*/

defined( 'ABSPATH' ) or die( 'No script kiddies please!' );

class ImageShortcodeImage
{
	private $post = NULL;
	private $meta = NULL;
	
	private $req_width = NULL;
	private $req_height = NULL;
	private $req_align = NULL;
	
	public function __construct($id) {
		$this->post = get_post($id);
		if ($this->isValidAttachment()) {
			$this->meta = wp_get_attachment_metadata($this->post->ID);
		}
	}
	
	public function isValidAttachment() {
		return (!is_null($this->post) and $this->post->post_type == 'attachment');
	}
	
	public function toHtml($custom_link_attributes=NULL, $custom_img_attributes=NULL) {
		if (!$this->isValidAttachment()) 
			return '[invalid attachment id]';
		
		$link_attributes = array();
		if (!is_null($custom_link_attributes)) {
			$link_attributes = array_merge($link_attributes, $custom_link_attributes);
		}
		array_push($link_attributes, 'href="' . wp_get_attachment_url($this->post->ID) . '"');
		
		$img_classes = array();
		array_push($img_classes, 'wp-image-' . $this->post->ID);
		
		if (!is_null($this->req_align)) {
			array_push($img_classes, 'align' . $this->req_align);
		}
		
		$dimensions = $this->getDisplayDimensions();
		
		$img_attributes = array();
		array_push($img_attributes, 'src="' . $this->getEmbedUrl($dimensions) . '"');		
		array_push($img_attributes, 'height="' . $dimensions['height'] . '"');
		array_push($img_attributes, 'width="' . $dimensions['width'] . '"');
		array_push($img_attributes, 'title="' . $this->post->post_title . '"');
		array_push($img_attributes, 'alt="' . $this->post->post_title . '"');
		array_push($img_attributes, 'class="' . implode(' ', $img_classes) . '"');
		
		$html = '<a ' . implode(' ', $link_attributes) . '><img ' . implode(' ', $img_attributes) . '></a>';
		
		return $html;
	}
	
	private function getDisplayDimensions() {		
		if (!is_null($this->req_width) and !is_null($this->req_height)) {
			return array(
				'width' => $this->req_width, 'height' => $this->req_height
			);
		}
		
		if (is_null($this->req_width) and is_null($this->req_height)) {
			return array( 
				'width' => $this->meta['width'], 'height' => $this->meta['height']
			);
		}
		
		$aspect_ratio = $this->meta['width'] / $this->meta['height'];
		if (!is_null($this->req_width)) {
			return array( 
				'width' => $this->req_width, 'height' => $this->req_width / $aspect_ratio
			);
		}
		
		if (!is_null($this->req_height)) {
			return array( 
				'width' => $this->req_height * $aspect_ratio, 'height' => $this->req_height
			);
		}
	}
	
	private function getEmbedUrl() {
		if (!isset($this->meta['sizes']))
			return wp_get_attachment_url($this->post->ID);
			
		if (is_null($dimensions)) 
			$dimensions = $this->getDisplayDimensions();
		
		$width = $dimensions['width'];
		$height = $dimensions['height'];
		
		$best_size_name = 'original';
		foreach ($this->meta['sizes'] as $name => $size) {
			if ($best_size_name == 'original') {
				$best_size = $this->meta;
			} else {
				$best_size = $this->meta['sizes'][$best_size_name];			
			}
			
			if ($height > $width) {
				if ($size['height'] >= $height and $size['height'] < $best_size['height']) {
					$best_size_name = $name;
				}
			} else {
				if ($size['width'] >= $width and $size['width'] < $best_size['width']) {
					$best_size_name = $name;
				}
			}
		}
		
		if ($best_size_name != 'original') {
			$src = wp_get_attachment_image_src($this->post->ID, $best_size_name);
			if ($src[3]) {
				return $src[0];
			}
		}
		
		return wp_get_attachment_url($this->post->ID);
	}
	
	public function parseAtts($atts) {
		$this->req_width = isset($atts['width']) ? intval($atts['width']) : NULL;
		$this->req_height = isset($atts['height']) ? intval($atts['height']) : NULL;
		$this->req_align = isset($atts['align']) ? $atts['align'] : NULL;
	}
}


function image_shortcode_insert($atts) {
	$id = $atts['id'];
	$image = new ImageShortcodeImage($id);
	$image->parseAtts($atts);
	return $image->toHtml(array(
		'data-rel="lightbox-0"'
	));
}

function image_shortcode_init() {
	add_shortcode('image', 'image_shortcode_insert');
}

add_action('init', 'image_shortcode_init');
?>