GD : Black background with imagecreatetruecolor

[Arnaud]

Hi everyone,

I'd like to use "imagecreatetruecolor" function in order to "cut and paste"
JPG files on a white background. It seems not to work correctly.

Here is my test scripts :

This one works perfectly :
<?
$im=imagecreate(50,50);
$COULEUR_BLANC=imagecolorallocate($im,255,255,255);
header ("Content-type: image/png");
ImagePNG($im);
imagedestroy($im);
?>

I obtain a white image but using GD 2.x, the "imagecopy" function fails.

This other script doesn't work :
<?
$im=imagecreatetruecolor(50,50);
$COULEUR_BLANC=imagecolorallocate($im,255,255,255);
header ("Content-type: image/png");
ImagePNG($im);
imagedestroy($im);
?>

I'm getting a black image.

My configuration is PHP 4.2.3 with gd2 running on Windows XP (I've also
tested it on my web provider machine - Linux with PHP 4.2.2)

Any help would be great.

Thanks in advance

Arnaud

[Morgan Hughes]

Post by Arnaud
Hi everyone,
I'd like to use "imagecreatetruecolor" function in order to "cut and paste"
JPG files on a white background. It seems not to work correctly.

This one bit me when I started working with GD 2.x as well. Simply draw
a filled rectangle over your entire canvas in the color you want:

<?
$im=imagecreatetruecolor(50,50);
$COULEUR_BLANC=imagecolorallocate($im,255,255,255);
imagefilledrectangle($im,0,0,49,49,$COULEUR_BLANC);
header ("Content-type: image/png");
ImagePNG($im);
imagedestroy($im);
?>

The reason seems to be that when you create an indexed-color image
(imagecreate()) gd sets all pixels to index 0, and when you allocate
your first color, that's index 0. Thus all background pixels magically
become that color.

When you use imagecreatetruecolor(), it sets all the pixels to black,
and you have to explicitly draw them in to get them white.
--
Morgan Hughes
C programmer and highly caffeinated mammal.
***@kyhm.com
ICQ: 79293356

[Arnaud]

Yeah !!! It works

Thanks Morgan

Arnaud

Post by Morgan Hughes

Post by Arnaud
Hi everyone,
I'd like to use "imagecreatetruecolor" function in order to "cut and paste"
JPG files on a white background. It seems not to work correctly.

This one bit me when I started working with GD 2.x as well. Simply draw
<?
$im=imagecreatetruecolor(50,50);
$COULEUR_BLANC=imagecolorallocate($im,255,255,255);
imagefilledrectangle($im,0,0,49,49,$COULEUR_BLANC);
header ("Content-type: image/png");
ImagePNG($im);
imagedestroy($im);
?>
The reason seems to be that when you create an indexed-color image
(imagecreate()) gd sets all pixels to index 0, and when you allocate
your first color, that's index 0. Thus all background pixels magically
become that color.
When you use imagecreatetruecolor(), it sets all the pixels to black,
and you have to explicitly draw them in to get them white.
--
Morgan Hughes
C programmer and highly caffeinated mammal.
ICQ: 79293356

[Van Andel, Robert]

Testing

Robbert van Andel

-----Original Message-----
From: Arnaud [mailto:***@free.fr]
Sent: Thursday, November 21, 2002 1:22 PM
To: php-***@lists.php.net
Subject: [PHP] GD : Black background with imagecreatetruecolor


Hi everyone,

I'd like to use "imagecreatetruecolor" function in order to "cut and paste"
JPG files on a white background. It seems not to work correctly.

Here is my test scripts :

This one works perfectly :
<?
$im=imagecreate(50,50);
$COULEUR_BLANC=imagecolorallocate($im,255,255,255);
header ("Content-type: image/png");
ImagePNG($im);
imagedestroy($im);
?>

I obtain a white image but using GD 2.x, the "imagecopy" function fails.

This other script doesn't work :
<?
$im=imagecreatetruecolor(50,50);
$COULEUR_BLANC=imagecolorallocate($im,255,255,255);
header ("Content-type: image/png");
ImagePNG($im);
imagedestroy($im);
?>

I'm getting a black image.

My configuration is PHP 4.2.3 with gd2 running on Windows XP (I've also
tested it on my web provider machine - Linux with PHP 4.2.2)

Any help would be great.

Thanks in advance

Arnaud
--
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