constrain.php

<?php
 
/**
 * Copyright (c) 2009 TJ Holowaychuk <tj@vision-media.ca> 
 * MIT Licensed
 */
 
define('GD_CONSTRAIN_DIMENSIONS_VERSION', '0.0.1');
 
class GD_Constrain_Dimensions {
  
  /**
   * Input image filepath.
   *
   * @var string
   */
   
  public $input_path;
  
  /**
   * Output image filepath.
   *
   * @var string
   */
   
  public $output_path;
  
  /**
   * Output image quality.
   *
   * @var int
   */
   
  public $quality = 90;
  
  /**
   * Constructor.
   *
   * @param string $input_path
   *   Path to the input image.
   *
   * @param string $output_path
   *   (optional) Path to output image. Defaults to
   *   using the $input_path provided.
   */
   
  public function __construct($input_path, $output_path = NULL) {
    $this->input_path = $input_path;
    if ($output_path) $this->output_path = $output_path;
    else $this->output_path = $input_path;
  }
  
  /**
   * Convert the image to its constrained dimensions.
   */
   
  public function constrain($target_width, $target_height) {
    if (!file_exists($this->input_path)) throw new Exception("input image '$this->input_path' does not exist");
    list($width, $height, $type, $attr) = getimagesize($this->input_path);
    $img = imagecreatefromjpeg($this->input_path);
    $canvas = imagecreatetruecolor($target_width, $target_height);
    $white = imagecolorallocate($canvas, 255, 255, 255);
    imagefill($canvas, 0, 0, $white);
    $dest_x = $target_width / 2 - $width;
    $dest_y = $target_height / 2 - $height;
    if ($width > $height) $ratio = $target_width / $width;
    else $ratio = $target_height / $height;
    $dest_width = $width * $ratio;
    $dest_height = $height * $ratio;
    $dest_x = ($target_width / 2) - ($dest_width / 2);
    $dest_y = ($target_height / 2) - ($dest_height / 2);
    imagecopyresampled($canvas, $img, $dest_x, $dest_y, 0, 0, $dest_width, $dest_height, $width, $height);
    imagejpeg($canvas, $this->output_path, $this->quality);
    imagedestroy($img);
    imagedestroy($canvas);
  }
  
}