PHP - How can I copy the image as transparent png - php

Question

First, I'm not master of PHP. I'm using a function for resize and crop images. It's working perfectly until I upload a transparent png. :)
It saves the png with black background. I found some answers on stackoverflow but I can't combine it with my codes.
Here is my function:
//resize and crop image
function resize_crop_image($max_width, $max_height, $source_file, $dst_dir, $quality = 90){
$imgsize = getimagesize($source_file);
$width = $imgsize[0];
$height = $imgsize[1];
$mime = $imgsize['mime'];
switch($mime){
case 'image/gif':
$image_create = "imagecreatefromgif";
$image = "imagegif";
$format = "gif";
break;
case 'image/png':
$image_create = "imagecreatefrompng";
$image = "imagepng";
$quality = 7;
$format = "png";
break;
case 'image/jpeg':
$image_create = "imagecreatefromjpeg";
$image = "imagejpeg";
$format = "jpg";
break;
default:
return false;
break;
}
$dst_img = imagecreatetruecolor($max_width, $max_height);
$src_img = $image_create($source_file);
$width_new = $height * $max_width / $max_height;
$height_new = $width * $max_height / $max_width;
//if the new width is greater than the actual width of the image, then the height is too large and the rest cut off, or vice versa
if($width_new > $width){
//cut point by height
$h_point = (($height - $height_new) / 2);
//copy image
imagecopyresampled($dst_img, $src_img, 0, 0, 0, $h_point, $max_width, $max_height, $width, $height_new);
}else{
//cut point by width
$w_point = (($width - $width_new) / 2);
imagecopyresampled($dst_img, $src_img, 0, 0, $w_point, 0, $max_width, $max_height, $width_new, $height);
}
// you can ignore these 4 lines. I'm using it for change the name.
$nameforimage = rand('11111111', '9999999999');
$nameforimage2 = rand('11111111', '9999999999');
$newname = $nameforimage."_".$nameforimage2;
$newdir = $dst_dir."".$newname.".".$format;
$image($dst_img, $newdir, $quality);
if($dst_img)imagedestroy($dst_img);
if($src_img)imagedestroy($src_img);
return $newname.".".$format;
}
EDIT:
Okay I've found a solution.
Just add these lines:
imagealphablending($dst_img, false);
imagesavealpha($dst_img, true);
$transparent = imagecolorallocatealpha($dst_img, 255, 255, 255, 127);
imagefilledrectangle($dst_img, 0, 0, $max_width, $max_height, $transparent);
After this line:
$dst_img = imagecreatetruecolor($max_width, $max_height);

Answer 1

You have to enable saving the alpha channel.
It can be done with imagesavealpha(), e.g.:
// As per the manual, alpha blending must be disabled
imagealphablending($dst_img, false);
imagesavealpha($dst_img, true);