Convert an image resource to grayscale.
Note that transparent GIFs loose transparency when desaturated.
$image: An image object. The $image->resource value will be modified by this call.
TRUE or FALSE, based on success.
function image_gd_desaturate(stdClass $image) {
// PHP installations using non-bundled GD do not have imagefilter.
if (!function_exists('imagefilter')) {
watchdog('image', 'The image %file could not be desaturated because the imagefilter() function is not available in this PHP installation.', array(
'%file' => $image->source,
));
return FALSE;
}
return imagefilter($image->resource, IMG_FILTER_GRAYSCALE);
}