Issue uploading PNG images with transparency? - php

Question

I'm having some issues uploading PNG images with transparency.
I upload, crop and insert the images in the DB and when I try to show them in the website they come up black. It's only happening with PNG images, for JPG, JPEG and GIF it's working perfect.
Can somebody help me with that?
Thanks in advance!
Example
This is my code:
public function create_square_image($original_file, $destination_file=NULL, $square_size = 100){
// get width and height of original image
$imagedata = getimagesize($original_file);
$original_width = $imagedata[0];
$original_height = $imagedata[1];
if($original_width > $original_height){
$new_height = $square_size;
$new_width = $new_height*($original_width/$original_height);
}
if($original_height > $original_width){
$new_width = $square_size;
$new_height = $new_width*($original_height/$original_width);
}
if($original_height == $original_width){
$new_width = $square_size;
$new_height = $square_size;
}
$new_width = round($new_width);
$new_height = round($new_height);
// load the image
if(substr_count(strtolower($original_file), ".jpg") or substr_count(strtolower($original_file), ".jpeg")){
$original_image = imagecreatefromjpeg($original_file);
}
if(substr_count(strtolower($original_file), ".gif")){
$original_image = imagecreatefromgif($original_file);
}
if(substr_count(strtolower($original_file), ".png")){
$original_image = imagecreatefrompng($original_file);
}
$smaller_image = imagecreatetruecolor($new_width, $new_height);
$square_image = imagecreatetruecolor($square_size, $square_size);
imagecopyresampled($smaller_image, $original_image, 0, 0, 0, 0, $new_width, $new_height, $original_width, $original_height);
if($new_width>$new_height){
$difference = $new_width-$new_height;
$half_difference = round($difference/2);
imagecopyresampled($square_image, $smaller_image, 0-$half_difference+1, 0, 0, 0, $square_size+$difference, $square_size, $new_width, $new_height);
}
if($new_height>$new_width){
$difference = $new_height-$new_width;
$half_difference = round($difference/2);
imagecopyresampled($square_image, $smaller_image, 0, 0-$half_difference+1, 0, 0, $square_size, $square_size+$difference, $new_width, $new_height);
}
if($new_height == $new_width){
imagecopyresampled($square_image, $smaller_image, 0, 0, 0, 0, $square_size, $square_size, $new_width, $new_height);
}
// if no destination file was given then display a png
if(!$destination_file){
imagepng($square_image,NULL,9);
}
// save the smaller image FILE if destination file given
if(substr_count(strtolower($destination_file), ".jpg")){
imagejpeg($square_image,$destination_file,100);
}
if(substr_count(strtolower($destination_file), ".gif")){
imagegif($square_image,$destination_file);
}
if(substr_count(strtolower($destination_file), ".png")){
imagepng($square_image,$destination_file,9);
}
imagedestroy($original_image);
imagedestroy($smaller_image);
imagedestroy($square_image);
}

Answer 1

You need to use imagesavealpha() in order to preserve the alpha channel when saving.