Description:
------------
This bug can be found when trying to make a thumbnail from a url (example: http://promote.opera.com/logos/Opera5_t.png) the png isn`t even transperant anymore unless these 3 lines of code are also added: 

$background = imagecolorallocate($thumb, 0, 0, 0);
ImageColorTransparent($thumb, $background); // make the new temp image all transparent
imagealphablending($thumb, false); // turn off the alpha blending to keep the alpha channel

i tried everything i could thing of but the quality stays different..

What the code below does is the following:
1. It downloaded the opera logo png image and makes a thumbnail of the URL!!
2. (after hitting F5) the code will make another thumbnail from the downloaded full scale image.
3. (after hitting F5 2nd time) the code will show both thumbnails and look at the quality difference!! and without the 3 lines posted above the "ugly" image has a black background!!

Reproduce code:
---------------
<?php
// Error Reporting
error_reporting(E_ALL);

// File and new size
if (file_exists('thumb_van_url.png') AND file_exists('thumb_van_path.png'))
{
    echo '<img src="./thumb_van_url.png"></img>';
    echo "Thumbnail made from URL";
    echo '<img src="./thumb_van_path.png"></img>';
    echo "This one is made from a PATH";
    exit;
}
elseif (file_exists('./Opera5_t.png'))
{
    $filename = 'Opera5_t.png';
    $mid = 'van_path';
}
else
{
    $filename = 'http://promote.opera.com/logos/Opera5_t.png';
    $mid = 'van_url';
    imagepng(imagecreatefrompng('http://promote.opera.com/logos/Opera5_t.png'), 'Opera5_t.png');
}

$percent = 0.1;

// Get new sizes
list($width, $height) = getimagesize($filename);
$newwidth = $width * $percent;
$newheight = $height * $percent;

// Load
$thumb = imagecreatetruecolor($newwidth, $newheight);
$source = imagecreatefrompng($filename);

$background = imagecolorallocate($thumb, 0, 0, 0);
ImageColorTransparent($thumb, $background); // make the new temp image all transparent
imagealphablending($thumb, false); // turn off the alpha blending to keep the alpha channel

// Resize
imagecopyresampled($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);

// Output
imagepng($thumb, 'thumb_' . $mid . '.png');
echo '<img src="./thumb_' . $mid . '.png"></img>';


// Content type
// header('Content-type: image/png');
// readfile('thumb_' . $mid . '.png');
?>



Expected result:
----------------
http://img393.imageshack.us/img393/2796/uitkomstvc4.png