imagecolortransparent
  (PHP 4, PHP 5)
imagecolortransparent — Define a color as transparent
  
 
  Description
  
   int imagecolortransparent
    ( resource $image
   [, int $color
  ] )
  
  
 
 
  Return Values
  
   The identifier of the new (or current, if none is specified)
   transparent color is returned.
  
  
 
  Notes
  Note: 
   
    Transparency is copied only with imagecopymerge() and
    true color images, not with imagecopy() or pallete images.
   
  
  Note: 
   
    The transparent color is a property of the image, transparency is not a
    property of the color. Once you have set a color to be the transparent
    color, any regions of the image in that color that were drawn previously
    will be transparent.