Keeping alpha channel with png's

Coder_10010011

Hello. I have a small problem. I'm trying to create a png image on the fly with text on it AND keep the alpha channel of the original png file.

Here is the code for the php file which generates the new png image:

MakeLabel.php

<?
	header("Content-type: image/png");

// Arguments:
// $text = The message you want on label
// $type = Base image to use (0 = Gold, 1 = Silver, 2 = Brass)

$BaseImage[0]="GoldBD.png";
$BaseImage[1]="SilverBD.png";
$BaseImage[2]="BrassBD.png";

if($type >= 3) die();

$FileName = "Images/".$BaseImage[$type];

$im = imagecreatefrompng($FileName);
$black = imagecolorallocate($im, 0, 0, 0);
$px = (imagesx($im) - 7.5 * strlen($text)) / 2;
imagestring($im, 3, $px, 9, $text, $black);
imagepng($im);
imagedestroy($im);
?>

Now, here is the html I am using to test it:

pngtest.html

<HTML>
	<BODY>
		<IMG src="Images/blank.png" style="filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(src='MakeLabel.php?text=Hello, Foo&type=0')"></IMG>
		<br>
		<IMG src="Images/blank.png" style="filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(src='Images/GoldBD.png')"></IMG>
	</BODY>
</BODY>

When displaying the html page, the top image has no alpha channel working in it at all (black box around the whole thing). It does spew out the image with "Hello, Foo" on it. It just has no transparency or transluceny in it. Surrounded by black.

The bottom image shows perfectly with the translucent shadow working:

So, what is missing in MakeLabel.php that tells it not to trash the alpha channel in the new image?

Thanks for any help. =)

onion2k

[man]imagealphablending/man;

Coder_10010011

Tried that. Doesn't work. New code looks like this:

<?
	header("Content-type: image/png");

// Arguments:
// $text = The message you want on label
// $type = Base image to use (0 = Gold, 1 = Silver, 2 = Brass)

$BaseImage[0]="GoldBD.png";
$BaseImage[1]="SilverBD.png";
$BaseImage[2]="BrassBD.png";

if($type >= 3) die();

$FileName = "Images/".$BaseImage[$type];

$im = imagecreatefrompng($FileName);
imagealphablending($im, true);
$black = imagecolorallocate($im, 0, 0, 0);
$px = (imagesx($im) - 7.5 * strlen($text)) / 2;
imagestring($im, 3, $px, 9, $text, $black);
imagepng($im);
imagedestroy($im);
?>

I've also tried a imagesavealpha() and it doesn't seem to work either.

Coder_10010011

So has anyone gotten this to work at all? I really have no idea what to try next.

Coder_10010011

Ok, figured it out on my own. Here is the solution in case anyone else thinks to ask about it here.

Need to add these 2 lines after $im = imagecreatefrompng($FileName);

imagealphablending($im,FALSE);
imagesavealpha($im,TRUE);

It works. I am happy. =)