#40601 [NEW]: imagesavealpha() has opposite effect on transparent color

[seth at pricepages dot org]

From: seth at pricepages dot org
Operating system: Mac 10.4
PHP version: 5.2.1
PHP Bug Type: GD related
Bug description: imagesavealpha() has opposite effect on transparent color

Description:
------------
The function imagesavealpha() has an opposite effect on the
output image if the color is marked as transparent. For
example, the code below should always create a clear image.
But it renders as black.

The interesting thing is that if you remove the imagesavealpha
, the image renders as expected (clear).

Reproduce code:
---------------
<?php
$img = imagecreatetruecolor(100,100);

$trans = imagecolorresolve($img,0,0,0);
imagecolortransparent($img, $trans);
imagealphablending($img, false);
imagefilledrectangle($img, 0,0, 100,100, $trans);

//Has opposite affect
imagesavealpha($img,true);

header('Content-Type: image/png');
imagepng($img);
?>

Expected result:
----------------
nothing (a clear image)

Actual result:
--------------
a solid black image

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[pajoye@php.net]

ID: 40601
Updated by: [email]pajoye@php.net[/email]
Reported By: seth at pricepages dot org
-Status: Open
+Status: Bogus
Bug Type: GD related
Operating System: Mac 10.4
PHP Version: 5.2.1
-Assigned To:
+Assigned To: pajoye
New Comment:

Transparent color and alpha cannot work together when you save a file.
PNG supports one or another not both (PNG is also the only format
supporting alpha).

You will get a warning/error in libpng if you try to do the same calls
(for example in C).

not a bug > bogus.



Previous Comments:
------------------------------------------------------------------------

[2007-02-23 03:04:57] seth at pricepages dot org

Description:
------------
The function imagesavealpha() has an opposite effect on the
output image if the color is marked as transparent. For
example, the code below should always create a clear image.
But it renders as black.

The interesting thing is that if you remove the imagesavealpha
, the image renders as expected (clear).

Reproduce code:
---------------
<?php
$img = imagecreatetruecolor(100,100);

$trans = imagecolorresolve($img,0,0,0);
imagecolortransparent($img, $trans);
imagealphablending($img, false);
imagefilledrectangle($img, 0,0, 100,100, $trans);

//Has opposite affect
imagesavealpha($img,true);

header('Content-Type: image/png');
imagepng($img);
?>

Expected result:
----------------
nothing (a clear image)

Actual result:
--------------
a solid black image


------------------------------------------------------------------------


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Edit this bug report at [url]http://bugs.php.net/?id=40601&edit=1[/url]