PNG Transparency Resize with SimpleImage.php Class - php

Question

I'm using a modified version of the SimpleImage.php class: http://www.white-hat-web-design.co.uk/articles/php-image-resizing.php
The edits I found on phpfreaks (http://www.phpfreaks.com/forums/index.php?topic=301811.0), but when I use, the png gets resized but the transparency is black.
I make the call like:
$max_width = 200; // set a max width
$max_height = 150; // set a max height
if($imgW > $imgH){ // width is greater
// resize to width up to max
if($imgW > $max_width) $image->resizeToWidth($max_width);
}
else { // height is greater
// resize to height up to max
if($imgH > $max_height) $image->resizeToHeight($max_height);
}
$image->save($_SERVER['DOCUMENT_ROOT']."/path/" . $new_filename);
I'm not sure what's missing. Any help is appreciated...
class SimpleImage {
var $image;
var $image_type;
function load($filename) {
$image_info = getimagesize($filename);
$this->image_type = $image_info[2];
if( $this->image_type == IMAGETYPE_JPEG ) {
$this->image = imagecreatefromjpeg($filename);
} elseif( $this->image_type == IMAGETYPE_GIF ) {
$this->image = imagecreatefromgif($filename);
} elseif( $this->image_type == IMAGETYPE_PNG ) {
$this->image = imagecreatefrompng($filename);
}
}
function save($filename, $image_type=IMAGETYPE_JPEG, $compression=75, $permissions=null) {
if( $image_type == IMAGETYPE_JPEG ) {
imagejpeg($this->image,$filename,$compression);
} elseif( $image_type == IMAGETYPE_GIF ) {
imagegif($this->image,$filename);
} elseif( $image_type == IMAGETYPE_PNG ) {
imagepng($this->image,$filename);
}
if( $permissions != null) {
chmod($filename,$permissions);
}
}
function output($image_type=IMAGETYPE_JPEG) {
if( $image_type == IMAGETYPE_JPEG ) {
imagejpeg($this->image);
} elseif( $image_type == IMAGETYPE_GIF ) {
imagegif($this->image);
} elseif( $image_type == IMAGETYPE_PNG ) {
imageAlphaBlending($this->image, true);
imageSaveAlpha($this->image, true);
imagepng($this->image);
}
}
function getWidth() {
return imagesx($this->image);
}
function getHeight() {
return imagesy($this->image);
}
function resizeToHeight($height) {
$ratio = $height / $this->getHeight();
$width = $this->getWidth() * $ratio;
$this->resize($width,$height);
}
function resizeToWidth($width) {
$ratio = $width / $this->getWidth();
$height = $this->getheight() * $ratio;
$this->resize($width,$height);
}
function scale($scale) {
$width = $this->getWidth() * $scale/100;
$height = $this->getheight() * $scale/100;
$this->resize($width,$height);
}
function resize($width,$height) {
// ADDED CODE IS HERE - NOT SURE WHY IT DOESN'T WORK FOR PNG
// Setup new image
$new_image = imagecreatetruecolor($width, $height);
// These parameters are required for handling PNG files.
imagealphablending($new_image, false);
imagesavealpha($new_image,true);
$transparent = imagecolorallocatealpha($new_image, 255, 255, 255, 127);
imagefilledrectangle($new_image, 0, 0, $width, $height, $transparent);
// Resize image
imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
$this->image = $new_image;
}
}

Answer 1

Now have the transparency working for PNG but not gif. Here are the edits to the specific functions in case it will help someone else:
Save Function:
function save($filename, $image_type=IMAGETYPE_JPEG, $compression=75, $permissions=null) {
// do this or they'll all go to jpeg
$image_type=$this->image_type;
if( $image_type == IMAGETYPE_JPEG ) {
imagejpeg($this->image,$filename,$compression);
} elseif( $image_type == IMAGETYPE_GIF ) {
imagegif($this->image,$filename);
} elseif( $image_type == IMAGETYPE_PNG ) {
// need this for transparent png to work
imagealphablending($this->image, false);
imagesavealpha($this->image,true);
imagepng($this->image,$filename);
}
if( $permissions != null) {
chmod($filename,$permissions);
}
}
Resize Function
function resize($width,$height,$forcesize='n') {
/* optional. if file is smaller, do not resize. */
if ($forcesize == 'n') {
if ($width > $this->getWidth() && $height > $this->getHeight()){
$width = $this->getWidth();
$height = $this->getHeight();
}
}
$new_image = imagecreatetruecolor($width, $height);
/* Check if this image is PNG or GIF, then set if Transparent*/
if(($this->image_type == IMAGETYPE_GIF) || ($this->image_type==IMAGETYPE_PNG)){
imagealphablending($new_image, false);
imagesavealpha($new_image,true);
$transparent = imagecolorallocatealpha($new_image, 255, 255, 255, 127);
imagefilledrectangle($new_image, 0, 0, $width, $height, $transparent);
}
imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
$this->image = $new_image;
}

Answer 2

The function imagecreatetruecolor() does not work with GIF's. Use the imagecreate method instead:
if($this->image_type == IMAGETYPE_GIF){
$new_image = imagecreate( $Width, $Height ); // for gif files
} else{
$new_image = imagecreatetruecolor($Width, $Height); // for all other files
}

Answer 3

I haven't been playing with GD for a long time myself (I prefer Imagemagick), but you could try setting alpha also to the source image before copying:
...
// ADDED CODE IS HERE ..
imagealphablending($this->image, true);
...
HTH.

Answer 4

I did the same as in this https://stackoverflow.com/a/6401135/262462 but edited this part
function save($filename, $image_type=IMAGETYPE_JPEG, $compression=75, $permissions=null) {
// do this or they'll all go to jpeg
$image_type=$this->image_type;
to this
function save($filename, $image_type="original", $compression=75, $permissions=null) {
if ($image_type=="original")
$image_type=$this->image_type;