(PECL haru >= 0.0.1)
HaruDoc::loadPNG — Load PNG image and return HaruImage instance
$filename
   [, bool $deferred = false
  ] )Loads a PNG image.
Libharu might be built without libpng support, in this case each call to this function would result in exception.
filename
     The name of a PNG image file.
deferred
     
       Do not load data immediately.
       You can set deferred parameter to TRUE for
       deferred data loading, in this case only size and color are loaded
       immediately. 
      
Returns a HaruImage instance.
发生错误时抛出 HaruException 异常。