Creating transparent gifs with php

[andrew_biggart]

I am currently trying to create an image uploading script that resizes the image if it over 570 pixels wide and saves the orignal image plus two different sized copies. I have got the script recreating jpg and png images, however when I upload a gif image the sized image no longer have a transparent background, they have a black background.

 

Can anyone advise me what I am doing wrong please?

 

<?php
session_start();

$upload_dir   = 'uploads/';
$medium_dir   = 'medium/';
$thumbs_dir   = 'thumbs/';
$medium_width = 570;
$thumb_width  = 50;

$allowed_ext = array('jpg','jpeg', 'png','gif');
date_default_timezone_set('Europe/Dublin');
$unique_id   = date("YmdHis");
$unique_id   = $unique_id . rand(0,999999999);

if(strtolower($_SERVER['REQUEST_METHOD']) != 'post'){
	exit_status('Error! Wrong HTTP method!');
}


if(array_key_exists('pic',$_FILES) && $_FILES['pic']['error'] == 0 ){

	$file_tmp   = $_FILES['pic']['tmp_name'];
	$file_name  = $_FILES['pic']['name'];
	$file_size  = $_FILES['pic']['size'];
	$file_ext   = get_extension($_FILES['pic']['name']);
	$file_new   = $unique_id . "." . $file_ext;
	$createdby  = $_SESSION["ufullname"];

	if(!in_array(get_extension($file_name),$allowed_ext)){
		exit_status('Only '.implode(',',$allowed_ext).' files are allowed!');
	}	

	// Check the width of the uploaded image
	list($file_width,$file_height) = getimagesize($file_tmp);

	if($file_width > $medium_width) {

		// Move the uploaded file from the temporary 
		// directory to the uploads folder:

		if(move_uploaded_file($file_tmp, $upload_dir . $file_new)){

			include('functions.php');

			connect();

			$link   = get_option('admin_url');

			$sql    = " INSERT into mediaT ( name, url, link, createdon, createdby ) VALUES ( '$name', '$upload_dir$file_new', '$link$upload_dir$file_new', NOW(), '$createdby' ) ";
			$result = mysql_query($sql);


			if($result) {

				if($file_ext == "jpg" || $file_ext == "jpeg" ){
					$src = imagecreatefromjpeg($upload_dir . $file_new);
				}
				else if($file_ext == "png"){
					$src = imagecreatefrompng($upload_dir . $file_new);
				}
				else if($file_ext == "gif"){
					$src = imagecreatefromgif($upload_dir . $file_new);
				}

				//Create medium image.

				$file_height_medium = ($file_height/$file_width) * $medium_width;
				$medium_image = imagecreatetruecolor($medium_width,$file_height_medium);

				//Create small image.

				$file_height_thumb = ($file_height/$file_width) * $thumb_width;
				$thumb_image = imagecreatetruecolor($thumb_width,$file_height_thumb);


				if($file_ext == "jpg" || $file_ext == "jpeg" ){
					imagecopyresized($medium_image,$src,0,0,0,0,$medium_width,$file_height_medium,$file_width,$file_height);
					imagecopyresized($thumb_image,$src,0,0,0,0,$thumb_width,$file_height_thumb,$file_width,$file_height);
					imagejpeg($medium_image,$upload_dir . $medium_dir . $file_new,100);
					imagejpeg($thumb_image,$upload_dir . $thumbs_dir . $file_new,100);
				}
				else if($file_ext == "png"){
					imagesavealpha($medium_image, true); 
					imagesavealpha($thumb_image, true);

					$color = imagecolorallocatealpha($medium_image,0x00,0x00,0x00,127); 
					$color2 = imagecolorallocatealpha($thumb_image,0x00,0x00,0x00,127);
					imagefill($medium_image, 0, 0, $color);
					imagefill($thumb_image, 0, 0, $color2);
					imagecopyresized($medium_image,$src,0,0,0,0,$medium_width,$file_height_medium,$file_width,$file_height);
					imagecopyresized($thumb_image,$src,0,0,0,0,$thumb_width,$file_height_thumb,$file_width,$file_height);
					imagepng($medium_image,$upload_dir . $medium_dir . $file_new);
					imagepng($thumb_image,$upload_dir . $thumbs_dir . $file_new);
				}
				else if($file_ext == "gif"){
					imagesavealpha($medium_image, true); 
					imagesavealpha($thumb_image, true);

					$color = imagecolorallocatealpha($medium_image,0x00,0x00,0x00,127);
					$color2 = imagecolorallocatealpha($thumb_image,0x00,0x00,0x00,127); 
					imagefill($medium_image, 0, 0, $color);
					imagefill($thumb_image, 0, 0, $color2);
					imagecopyresized($medium_image,$src,0,0,0,0,$medium_width,$file_height_medium,$file_width,$file_height);
					imagecopyresized($thumb_image,$src,0,0,0,0,$thumb_width,$file_height_thumb,$file_width,$file_height);
					imagegif($medium_image,$upload_dir . $medium_dir . $file_new);
					imagegif($thumb_image,$upload_dir . $thumbs_dir . $file_new);
				}

				exit_status('File was uploaded successfuly!');

				imagedestroy($src);
				imagedestroy($medium_image);
				imagedestroy($thumb_image);	

			}
			else {
				exit_status('Error! <i>File couldnt be saved to the database.</i>');
			}
		}
	}
	else {


		// Move the uploaded file from the temporary 
		// directory to the uploads folder:

		if(move_uploaded_file($file_tmp, $upload_dir . $file_new)){

			include('functions.php');

			connect();

			$link   = get_option('admin_url');

			$sql    = " INSERT into mediaT ( name, url, link, createdon, createdby ) VALUES ( '$name', '$upload_dir$file_new', '$link$upload_dir$file_new', NOW(), '$createdby' ) ";
			$result = mysql_query($sql);

			exit_status('File was uploaded successfuly!');
		}
	}

}

exit_status('Something went wrong with your upload!');


// Helper functions

function exit_status($str){
	echo json_encode(array('status'=>$str));
	exit;
}

function get_extension($file_name){
	$ext = explode('.', $file_name);
	$ext = array_pop($ext);
	return strtolower($ext);
}
?>

[andrew_biggart]

Does anyone have any advice?

[xyph]

There's plenty on Google about this. GIF's alpha isn't a 'channel', it's a 'colour' on the palette, so it works a little differently, and will give you potentially UGLY results.