(PHP 5 >= 5.5.0, PHP 7)
imagecrop — Crop an image to the given rectangle
$image
   , array $rect
   ) : resource
   Crops an image to the given rectangular area and returns the resulting image.
   The given image is not modified.
  
image由图象创建函数(例如imagecreatetruecolor())返回的图象资源。
rect
      The cropping rectangle as array with keys
      x, y, width and
      height.
     
   Return cropped image resource on success 或者在失败时返回 FALSE.
  
Example #1 imagecrop() example
This example shows how to crop an image to a square area.
<?php
$im = imagecreatefrompng('example.png');
$size = min(imagesx($im), imagesy($im));
$im2 = imagecrop($im, ['x' => 0, 'y' => 0, 'width' => $size, 'height' => $size]);
if ($im2 !== FALSE) {
    imagepng($im2, 'example-cropped.png');
    imagedestroy($im2);
}
imagedestroy($im);
?>