Resize Images (supports transparency) - php

Question

I need to get a preview of an image after upload.According to me , it will be a better solution to store the thumbnails on the server as a cache.However the function that i am using currently doesn't seems to support transparency.It just fill the background with black
Here is the function that i am using
<?php
/**
* Resize image class will allow you to resize an image
*
* Can resize to exact size
* Max width size while keep aspect ratio
* Max height size while keep aspect ratio
* Automatic while keep aspect ratio
*/
class ResizeImage
{
private $ext;
private $image;
private $newImage;
private $origWidth;
private $origHeight;
private $resizeWidth;
private $resizeHeight;
/**
* Class constructor requires to send through the image filename
*
* #param string $filename - Filename of the image you want to resize
*/
public function __construct( $filename )
{
if(file_exists($filename))
{
$this->setImage( $filename );
} else {
throw new Exception('Image ' . $filename . ' can not be found, try another image.');
}
}
/**
* Set the image variable by using image create
*
* #param string $filename - The image filename
*/
private function setImage( $filename )
{
$size = getimagesize($filename);
$this->ext = $size['mime'];
switch($this->ext)
{
// Image is a JPG
case 'image/jpg':
case 'image/jpeg':
// create a jpeg extension
$this->image = imagecreatefromjpeg($filename);
break;
// Image is a GIF
case 'image/gif':
$this->image = #imagecreatefromgif($filename);
break;
// Image is a PNG
case 'image/png':
$this->image = #imagecreatefrompng($filename);
break;
// Mime type not found
default:
throw new Exception("File is not an image, please use another file type.", 1);
}
$this->origWidth = imagesx($this->image);
$this->origHeight = imagesy($this->image);
}
/**
* Save the image as the image type the original image was
*
* #param String[type] $savePath - The path to store the new image
* #param string $imageQuality - The qulaity level of image to create
*
* #return Saves the image
*/
public function saveImage($savePath, $imageQuality="100", $download = false)
{
switch($this->ext)
{
case 'image/jpg':
case 'image/jpeg':
// Check PHP supports this file type
if (imagetypes() & IMG_JPG) {
imagejpeg($this->newImage, $savePath, $imageQuality);
}
break;
case 'image/gif':
// Check PHP supports this file type
if (imagetypes() & IMG_GIF) {
imagegif($this->newImage, $savePath);
}
break;
case 'image/png':
$invertScaleQuality = 9 - round(($imageQuality/100) * 9);
// Check PHP supports this file type
if (imagetypes() & IMG_PNG) {
imagepng($this->newImage, $savePath, $invertScaleQuality);
}
break;
}
if($download)
{
header('Content-Description: File Transfer');
header("Content-type: application/octet-stream");
header("Content-disposition: attachment; filename= ".$savePath."");
readfile($savePath);
}
imagedestroy($this->newImage);
}
/**
* Resize the image to these set dimensions
*
* #param int $width - Max width of the image
* #param int $height - Max height of the image
* #param string $resizeOption - Scale option for the image
*
* #return Save new image
*/
public function resizeTo( $width, $height, $resizeOption = 'default' )
{
switch(strtolower($resizeOption))
{
case 'exact':
$this->resizeWidth = $width;
$this->resizeHeight = $height;
break;
case 'maxwidth':
$this->resizeWidth = $width;
$this->resizeHeight = $this->resizeHeightByWidth($width);
break;
case 'maxheight':
$this->resizeWidth = $this->resizeWidthByHeight($height);
$this->resizeHeight = $height;
break;
default:
if($this->origWidth > $width || $this->origHeight > $height)
{
if ( $this->origWidth > $this->origHeight ) {
$this->resizeHeight = $this->resizeHeightByWidth($width);
$this->resizeWidth = $width;
} else if( $this->origWidth < $this->origHeight ) {
$this->resizeWidth = $this->resizeWidthByHeight($height);
$this->resizeHeight = $height;
}
} else {
$this->resizeWidth = $width;
$this->resizeHeight = $height;
}
break;
}
$this->newImage = imagecreatetruecolor($this->resizeWidth, $this->resizeHeight);
imagecopyresampled($this->newImage, $this->image, 0, 0, 0, 0, $this->resizeWidth, $this->resizeHeight, $this->origWidth, $this->origHeight);
}
/**
* Get the resized height from the width keeping the aspect ratio
*
* #param int $width - Max image width
*
* #return Height keeping aspect ratio
*/
private function resizeHeightByWidth($width)
{
return floor(($this->origHeight/$this->origWidth)*$width);
}
/**
* Get the resized width from the height keeping the aspect ratio
*
* #param int $height - Max image height
*
* #return Width keeping aspect ratio
*/
private function resizeWidthByHeight($height)
{
return floor(($this->origWidth/$this->origHeight)*$height);
}
}
?>
It would be awesome if anyone could modify it to make it handle images with transparent background.
In case you have a better function please share
Kind Regards

Answer 1

Your class handles jpeg and png files also so you will need to check the type and make the changes only if it is png:
relace this
$this->newImage = imagecreatetruecolor($this->resizeWidth, $this->resizeHeight);
with this
$this->newImage = imagecreatetruecolor($this->resizeWidth, $this->resizeHeight);
imagesavealpha($this->newImage, true);
$transparent_color = imagecolorallocatealpha($this->newImage, 0, 0, 0, 127);
imagefill($this->newImage, 0, 0, $transparent_color);