减少png图片的大小而不会失去透明度

Question

I am trying to reduce image size by using the following function. But when I use an image that has transparency, this function repeats the image in transparency pixels and makes distortions. How can I reduce png image without losing transparency?

 function compress($source, $destination, $quality) 
 { 
     $info = getimagesize($source); 
     if ($info['mime'] == 'image/jpeg') 
        $image = imagecreatefromjpeg($source); 
     else if ($info['mime'] == 'image/gif') 
        $image = imagecreatefromgif($source); 
     else if ($info['mime'] == 'image/png') 
        $image = imagecreatefrompng($source); 

     imagejpeg($image, $destination, $quality); 
     return $destination; 
 } 

 $source_img = 'source.png'; 
 $destination_img = 'destination.png'; 
 $d = compress($source_img, $destination_img, 90); 

Answer 1

Change and add a couple of lines to your compress function :

function compress($source, $destination, $quality) 
{ 
    $info = getimagesize($source); 
    if ($info['mime'] == 'image/jpeg') 
       $image = imagecreatefromjpeg($source);
       imagejpeg($image, $destination, $quality); //Compress with jpg
    else if ($info['mime'] == 'image/gif') 
      $image = imagecreatefromgif($source); 
    else if ($info['mime'] == 'image/png') 
      $image = imagecreatefrompng($source); 
      imagepng($image, $destination, $quality); //Compress with png !!


   return $destination; 
} 

$source_img = 'source.png'; 
$destination_img = 'destination.png'; 
$d = compress($source_img, $destination_img, 90); 

Its important understand why the image gets with black background color when is a png , thats due to the transparency. JPEG format doesn't allow you to have a image with transparency , only PNG format supports it, so its only matter of call the right function in every case.

This script should work fine , if previously was working. Please try it.