How to clone a gd resource in PHP

Question

I'm looking for cloning an image in PHP created with imagecreatetruecolor or some other image creation function..

As it was said in the comment, no you can't do a simple affection like :

$copy = $original;

This because ressources are reference and could not be copied like scalar values.

Example :

$a = imagecreatetruecolor(10,10);
$b = $a;

var_dump($a, $b);

// resource(2, gd)

// resource(2, gd)

Answer 1

This little function will clone an image resource while retaining the alpha channel (transparency).

function _clone_img_resource($img) {

  //Get width from image.
  $w = imagesx($img);
  //Get height from image.
  $h = imagesy($img);
  //Get the transparent color from a 256 palette image.
  $trans = imagecolortransparent($img);

  //If this is a true color image...
  if (imageistruecolor($img)) {

    $clone = imagecreatetruecolor($w, $h);
    imagealphablending($clone, false);
    imagesavealpha($clone, true);
  }
  //If this is a 256 color palette image...
  else {

    $clone = imagecreate($w, $h);

    //If the image has transparency...
    if($trans >= 0) {

      $rgb = imagecolorsforindex($img, $trans);

      imagesavealpha($clone, true);
      $trans_index = imagecolorallocatealpha($clone, $rgb['red'], $rgb['green'], $rgb['blue'], $rgb['alpha']);
      imagefill($clone, 0, 0, $trans_index);
    }
  }

  //Create the Clone!!
  imagecopy($clone, $img, 0, 0, 0, 0, $w, $h);

  return $clone;
}

Answer 2

So, the solution found was in the comment, and this is an implementation of it in a Image management class :

public function __clone() {
    $original = $this->_img;
    $copy = imagecreatetruecolor($this->_width, $this->_height);

    imagecopy($copy, $original, 0, 0, 0, 0, $this->_width, $this->_height);

    $this->_img = $copy;
}

Answer 3

Much simpler code, one line, handle transparency:

function clone_img_resource($img) {
    return imagecrop($img, array('x'=>0,'y'=>0,'width'=>imagesx($img),'height'=>imagesy($img)));
}