Description:
------------
I wrote a small piece of code using that uses the GD module to apply a color-table to a gray-scale image.

In newer versions of PHP, however, the script only outputs grayscale images, with no error message.

Furthermore, outputting the contents of imagecolorsforindex shows that the script is still reading the palette properly, so it must have something to do with the next step (imagecolorset).

Any ideas?

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System 1 (non-working): 

Ubuntu 9.04 Linux 2.6.28-11-generic
PHP 5.2.6-3ubuntu4.1 with Suhosin-Patch 0.9.6.2 (cli) (built: Apr 23 2009 14:35:05)
gd 2.0.36~rc1~dfsg-3ubuntu1

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System 2 (non-working):

Fedora 11 Beta Linux 2.6.29.1-111.fc11.i586
PHP 5.2.9
gd 2.0.35

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System 3 (WORKING):
Ubuntu 8.10 Linux 2.6.27-11-generic
PHP 5.2.6-2ubuntu4.1 with Suhosin-Patch 0.9.6.2 (cli) (built: Feb 11 2009 20:38:24)
gd 2.0.36~rc1~dfsg-3ubuntu1

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(Originally reported downstream at:
https://bugs.edge.launchpad.net/ubuntu/+source/php5/+bug/368036)

Reproduce code:
---------------
/**
 * Takes a grayscale PNG and modifies it's index to use 256-color 
 * lookup table then outputs it as an 8-bit JPEG image, or 8-bit 
 * paletted PNG.
 *
 * Sample image and color-table:
 *
 * http://launchpadlibrarian.net/26034594/eit_grayscale.png
 * http://launchpadlibrarian.net/26034597/ctable_eit304.png
 */

$gd = imagecreatefrompng("eit_grayscale.png");
$ctable = imagecreatefrompng("ctable_eit304.png");

for ($i = 0; $i <= 255; $i++) {
 $rgba = imagecolorsforindex($ctable, $i);
 imagecolorset($gd, $i, $rgba["red"], $rgba["green"], $rgba["blue"]);
}

imagejpeg($gd, "eit_final.jpg", 75);
imagedestroy($gd);
imagedestroy($ctable);

Expected result:
----------------
Outputs a 8-bit color JPEG. (http://launchpadlibrarian.net/26034598/eit_final_ubuntu810.jpg)

Actual result:
--------------
Outputs a 8-bit grayscale JPEG. (http://launchpadlibrarian.net/26034602/eit_final_ubuntu904.jpg)