Make resized image transparent - php

Question

I use this code to upload images to my server. But for some reason my thumbnails get a black background instead of being transparent as they originally was.
I've tried using this "guide": http://www.akemapa.com/2008/07/10/php-gd-resize-transparent-image-png-gif/
But without success. I have no idea how I implement that piece of code into the one I use.
If anyone can help, please do so :)
<?php
//define a maxim size for the uploaded images
define ("MAX_SIZE","10240");
// define the width and height for the thumbnail
// note that theese dimmensions are considered the maximum dimmension and are not fixed,
// because we have to keep the image ratio intact or it will be deformed
define ("WIDTH","200");
define ("HEIGHT","200");
// this is the function that will create the thumbnail image from the uploaded image
// the resize will be done considering the width and height defined, but without deforming the image
function make_thumb($img_name,$filename,$new_w,$new_h)
{
//get image extension.
$ext=getExtension($img_name);
//creates the new image using the appropriate function from gd library
if(!strcmp("jpg",$ext) || !strcmp("jpeg",$ext))
$src_img=imagecreatefromjpeg($img_name);
if(!strcmp("png",$ext))
$src_img=imagecreatefrompng($img_name);
if(!strcmp("gif",$ext))
$src_img=imagecreatefromgif($img_name);
//gets the dimmensions of the image
$old_x=imageSX($src_img);
$old_y=imageSY($src_img);
// next we will calculate the new dimmensions for the thumbnail image
// the next steps will be taken:
// 1. calculate the ratio by dividing the old dimmensions with the new ones
// 2. if the ratio for the width is higher, the width will remain the one define in WIDTH variable
// and the height will be calculated so the image ratio will not change
// 3. otherwise we will use the height ratio for the image
// as a result, only one of the dimmensions will be from the fixed ones
$ratio1=$old_x/$new_w;
$ratio2=$old_y/$new_h;
if($ratio1>$ratio2) {
$thumb_w=$new_w;
$thumb_h=$old_y/$ratio1;
}
else {
$thumb_h=$new_h;
$thumb_w=$old_x/$ratio2;
}
// we create a new image with the new dimmensions
$dst_img=ImageCreateTrueColor($thumb_w,$thumb_h);
// resize the big image to the new created one
imagecopyresampled($dst_img,$src_img,0,0,0,0,$thumb_w,$thumb_h,$old_x,$old_y);
// output the created image to the file. Now we will have the thumbnail into the file named by $filename
if(!strcmp("png",$ext))
imagepng($dst_img,$filename);
else
imagejpeg($dst_img,$filename);
imagegif($dst_img,$filename);
//destroys source and destination images.
imagedestroy($dst_img);
imagedestroy($src_img);
}
// This function reads the extension of the file.
// It is used to determine if the file is an image by checking the extension.
function getExtension($str) {
$i = strrpos($str,".");
if (!$i) { return ""; }
$l = strlen($str) - $i;
$ext = substr($str,$i+1,$l);
return $ext;
}
// This variable is used as a flag. The value is initialized with 0 (meaning no error found) and it will be changed to 1 if an errro occures. If the error occures the file will not be uploaded.
$errors=0;
// checks if the form has been submitted
if(isset($_POST['Submit']))
{
//reads the name of the file the user submitted for uploading
$image=$_FILES['image']['name'];
// if it is not empty
if ($image)
{
// get the original name of the file from the clients machine
$filename = stripslashes($_FILES['image']['name']);
// get the extension of the file in a lower case format
$extension = getExtension($filename);
$extension = strtolower($extension);
// if it is not a known extension, we will suppose it is an error, print an error message and will not upload the file, otherwise we continue
if (($extension != "jpg") && ($extension != "jpeg") && ($extension != "png") && ($extension != "gif"))
{
echo '<h1>Unknown extension!</h1>';
$errors=1;
}
else
{
// get the size of the image in bytes
// $_FILES[\'image\'][\'tmp_name\'] is the temporary filename of the file in which
//the uploaded file was stored on the server
$size=getimagesize($_FILES['image']['tmp_name']);
$sizekb=filesize($_FILES['image']['tmp_name']);
//compare the size with the maxim size we defined and print error if bigger
if ($sizekb > MAX_SIZE*10240)
{
echo '<h1>You have exceeded the size limit!</h1>';
$errors=1;
}
//we will give an unique name, for example the time in unix time format
$image_name=time().'.'.$extension;
//the new name will be containing the full path where will be stored (images folder)
$newname="../images/uploads/".$image_name;
$copied = copy($_FILES['image']['tmp_name'], $newname);
//we verify if the image has been uploaded, and print error instead
if (!$copied)
{
echo '<h1>Copy unsuccessfull!</h1>';
$errors=1;
}
else
{
// the new thumbnail image will be placed in images/thumbs/ folder
$thumb_name='../images/uploads/thumbs/thumb_'.$image_name;
// call the function that will create the thumbnail. The function will get as parameters the image name, the thumbnail name and the width and height desired for the thumbnail
$thumb=make_thumb($newname,$thumb_name,WIDTH,HEIGHT);
}} }}

Answer 1

Try including imagesavealpha() for PNG's
if(!strcmp("png",$ext))
{
$src_img=imagecreatefrompng($img_name);
imagesavealpha($src_img, true);
}
And read into imagecolortransparent() for GIF files to see if you can find a solution here, messy though.