Question

I’m trying to resize a PNG transparent image using the following code:

$src=ImageCreateFrompng($uploadedfile);
$background=imagecolorallocate($src,0,0,0);
imagecolortransparent($src,$background);
imagealphablending($src,false);
imagesavealpha($src,true);
$dst=ImageCreateTrueColor($tn_width,$tn_height);
imagecopyresampled($dst,$src,0,0,0,0,$tn_width,$tn_height,$width,$height);
Imagepng($dst,$dstfile);

I used imagealphablending($src,false) and imagesavealpha($src,true) but it still uploads an image with a black background instead of a transparent one.

Where’s the problem?

Answer 1

This is because you copy transparent image on a black one. Your false setting for aplhablending only applyes to original image, so when you copy on new image, aplha blending is turned on.
Your code needs just a little improvement:

$transparent = imagecolorallocatealpha($dst, 0,0,0,127);  //Transparent background color
imagealphablending($dst,false);            //Not to compound transparent colors with opaque
imagesavealpha($dst,true);                 //Allow transparency
imagefilledrectangle($dst, 0, 0, imagesx($dst), imagesy($dst), $transparent);   //Give the destination image transparent background
//Now you can copy

OR JUST

imagealphablending($dst,false);   //I'm not 100% sure this will make it, but its worth a try