Transparent GIF problem

[petersJazz]

hi, have problem with transparent GIF. From one gif I want to extract a part and convert black (0,0,0) to transparent. Anyone understand why it wont work? Why doesnt black convert to transparent?

  $im1=imagecreatefromgif($file1);
  $im2=imagecreatetruecolor(30,30);
  $black = imagecolorallocate($im2, 0, 0, 0);
  imagecolortransparent($im2,$black);
  imagecopy($im2,$im1,0,0,0,0,30,30);
  imagecolortransparent($im2,$black);
  imagegif($im2,$file2);