<?php
/**
 * img_resize_crop
 * Resizes an image to a specific size, cropping if necessary, allows center-weighting.
 *
 * @param Resource $src - GD Resource Image to use.
 * @param Integer $twidth - Thumbnail width
 * @param Integer $theight - Thumbnail height
 * @param Integer $center_x - The x value of the target center location, leaving it at -1 autocalculates. [Default: -1]
 * @param Integer $center_y - The y value of the target center location, leaving it at -1 autocalculates. [Default: -1]
 * @param String $method - Method to use for the resize.  [Default:suggest]
 *   'suggest' (provided center coordinate is only guaranteed to be in the picture.)
 *   'force' (The provided coordinate is forced into being the center, additional data is trimmed to ensure this.)
 *   'onlycrop' (Not sure why you would use this, but only performs cropping.)
 * @param Boolean $sharpen - Specify whether or not to sharpen the resultant thumbnail [Default:true]
 * @param Int $evil_threshold - Maximum thumbnail width/height to prevent attempts at evil. [Default:1024]
 */
function img_resize_crop($src, $twidth, $theight, $center_x = -1, 
    $center_y = -1, $method = 'suggest', $sharpen = true, $evil_threshold = 1024)
{
   /*Set defaults if they are not provided.*/
   if($center_x == -1 || ($method == 'force' && $center_x == 0))
   {
      $center_x = floor(imagesx($src)/2);
   }
 
   if($center_y == -1 || ($method == 'force' && $center_y == 0))
   {
      $center_y = floor(imagesy($src)/2);
   }
 
   /* Prevent evil */
   if($twidth > $evil_threshold) $twidth = $evil_threshold;
   if($theight > $evil_threshold) $theight = $evil_threshold;
 
 
   /*  The ratio of the thumbnail and the ratio 
    of the original image.*/
   $t_ratio = $twidth / $theight;
   $o_ratio = imagesx($src) / imagesy($src);
   $new = imagecreatetruecolor($twidth, $theight);
 
   /*Ideally, we'll want to grab as much of 
     the source image as possible.
 
     So we need to figure out how much to grab based on 
     the ratios of the desired thumbnail and the original
     image.*/
   if($t_ratio > $o_ratio)
   {
      $i_width = imagesx($src);
      $i_height = floor($i_width / $t_ratio);
   }
   else
   {
      $i_height = imagesy($src);
      $i_width = floor($i_height * $t_ratio);
   }
 
   /*Calculate the upper-left corner of the 
     source image grab area.  These will be 
     adjusted differently based on the method selected.*/
   $s_x = $center_x - floor($i_width/2);
   $s_y = $center_y - floor($i_height/2);
 
 
 
   switch($method)
   {
      case 'onlycrop':  
         $i_width = (imagesx($src) > $twidth) ? $twidth : imagesx($src);
         $i_height = (imagesy($src) > $theight) ? $theight : imagesy($src);
         $s_x = $center_x - floor($i_width/2);
         $s_y = $center_y - floor($i_height/2);   
 
         /*Make sure we're inside the left and top boundaries.*/
         $s_x = ($s_x < 0) ? 0 : $s_x;
         $s_y = ($s_y < 0) ? 0 : $s_y;
 
         /*Make sure we're inside the bottom and right boundaries.*/
         $s_x = ($center_x + ceil($i_width/2) > imagesx($src)) ? imagesx($src) - $i_width : $s_x;
         $s_y = ($center_y + ceil($i_height/2) > imagesy($src)) ? imagesy($src) - $i_height : $s_y;  
 
         break;      
      default:
      case 'suggest':
         /*Condition: Crop is thinner (ratio-wise) than the original image.*/
         if($t_ratio <= $o_ratio)
         {
            $s_y = 0;
            $s_x = ($s_x < 0) ? 0 : $s_x;
            $s_x = ($center_x + ceil($i_width/2) > imagesx($src)) ? imagesx($src) - $i_width : $s_x;
         }
         else /*Condition: Crop is wider (ratio-wise) than the original image.*/
         {
            $s_x = 0;
            $s_y = ($s_y < 0) ? 0 : $s_y;
            $s_y = ($center_y + ceil($i_height/2) > imagesy($src)) ? imagesy($src) - $i_height : $s_y;   
         }
         break;
      case 'force':
         /*Condition: Crop is thinner (ratio-wise) than the original image.*/
         if($t_ratio <= $o_ratio)
         {
            /*Find the maximum possible height with the requested center_y.*/
            $i_height = ($center_y > floor(imagesy($src)/2)) ? (imagesy($src) - $center_y) * 2 : $center_y * 2;
            $i_width = floor($i_height * $t_ratio); /*Height for said width.*/
 
            /*If that puts the source box out of bounds, we'll need to proportionally scale down.*/
            if($center_x - floor($i_width/2) < 0 || $center_x + floor($i_width/2) > imagesx($src))
            {
               /*Minimum width.*/
               $i_width = ($center_x > floor(imagesx($src)/2)) ? (imagesx($src) - $center_x) * 2 : $center_x * 2;
               $i_height = floor($i_width / $t_ratio);
            }
            /*Recalculate source x and y*/
            $s_x = $center_x - floor($i_width/2);
            $s_y = $center_y - floor($i_height/2);            
         }
         else /*Condition: Crop is wider (ratio-wise) than the original image.*/
         {
            /*Find the maximum possible width with the requested center_x.*/
            $i_width = ($center_x > floor(imagesx($src)/2)) ? (imagesx($src) - $center_x) * 2 : $center_x * 2;
            $i_height = floor($i_width / $t_ratio); /*Height for said width.*/
 
            /*If that puts the source box out of bounds, we'll need to proportionally scale down.*/
            if($center_y - floor($i_height/2) < 0 || $center_y + floor($i_height/2) > imagesy($src))
            {
               /*Minimum height.*/
               $i_height = ($center_y > floor(imagesy($src)/2)) ? (imagesy($src) - $center_y) * 2 : $center_y * 2;
               $i_width = $i_height * $t_ratio;
            }
            /*Recalculate source x and y*/
            $s_x = $center_x - floor($i_width/2);
            $s_y = $center_y - floor($i_height/2);
         }
 
         break;
   }
 
   imagecopyresampled($new, $src, 
     /*Destination Coords*/
     0,0,
     /*Source Coords*/
     $s_x,$s_y,
     /*Destination Geometry*/
     $twidth, $theight,
     /*Source Geometry*/
     $i_width, $i_height
     );
 
   if($sharpen)
   {
      $sharpen_matrix = array(array(-1,-1,-1),array(-1,16,-1),array(-1,-1,-1));
      $divisor = 8;
      $offset = 0;
 
      imageconvolution($new, $sharpen_matrix, $divisor, $offset);
   }
 
   return $new;
}