bool imagecolordeallocate ( resource $image , int $color )

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

$im = @imagecreate(100, 50) or die("不能初始化新的 GD 图像流");

$background_color = imagecolorallocate($im, 255, 255, 255); 
$text_color = imagecolorallocate($im, 233, 14, 91);

imagestring($im, 1, 5, 5,  "A Simple Text String", $text_color);
imagecolordeallocate($im, $background_color);
imagepng($im);
imagedestroy($im);