(PHP 4, PHP 5, PHP 7)
imagepng — Output a PNG image to either the browser or a file
$image
   [, string $filename
   [, int $quality
   [, int $filters
  ]]] )
   Outputs or saves a PNG image from the given 
   image.
  
imageAn image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
filenameThe path to save the file to. If not set or NULL, the raw image stream will be outputted directly.
Note:
NULLis invalid if thequalityandfiltersarguments are not used.
qualityCompression level: from 0 (no compression) to 9.
filters
       Allows reducing the PNG file size. It is a bitmask field which may be
       set to any combination of the PNG_FILTER_XXX 
       constants. PNG_NO_FILTER or 
       PNG_ALL_FILTERS may also be used to respectively
       disable or activate all filters.
      
   Returns TRUE on success or FALSE on failure.
  
| Version | Description | 
|---|---|
| 5.1.3 | Added the filtersparameter. | 
| 5.1.2 | Added the qualityparameter. | 
<?php
$im = imagecreatefrompng("test.png");
header('Content-Type: image/png');
imagepng($im);
imagedestroy($im);
?>