Interactively Crop Image via PHP (GD/GD2 Library):
imagecopyresampled() function of php

imagecopyresampled ( 

	$dst_image: ,

	$src_image: ,

	$dst_x: ,

	$dst_y: ,

	$src_x: ,

	$src_y: ,

	$dst_width: ,

	$dst_height: ,

	$src_width: ,

	$src_height: ,

	
	

);

 FOUR RECTANGLES

                  $src_image                                   $dst_image
+------------+---------------------------------+   +------------+--------------------+
|            |                                 |   |            |                    |
|            |                                 |   |         $dst_y                  |
|            |                                 |   |            |                    |
|         $src_y                               |   +-- $dst_x --+----$dst_width----+ |
|            |                                 |   |            |                  | |
|            |                                 |   |            |    Resampled     | |
|            |                                 |   |            |                  | |
+-- $src_x --+------ $src_width ------+        |   |       $dst_height             | |
|            |                        |        |   |            |                  | |
|            |                        |        |   |            |                  | |
|            |                        |        |   |            |                  | |
|            |                        |        |   |            +------------------+ |
|            |        Sample          |        |   |                                 |
|            |                        |        |   |                                 |
|            |                        |        |   |                                 |
|       $src_height                   |        |   |                                 |
|            |                        |        |   +---------------------------------+
|            |                        |        |
|            |                        |        |
|            +------------------------+        |
|                                              |
|                                              |
+----------------------------------------------+
		
		
// general
imagecopyresampled ( $dst_image, $src_image, $dst_x, $dst_y, $src_x, $src_y, $dst_width, $dst_height, $src_width, $src_height );