CODE – Except category

I have this code:

/**
	 * Display Latest posts
	 */
	static function showLatest( $posts = 5, $size = 45 ) {
		global $post;
		$latest = get_posts( array( 'suppress_filters' => false, 'ignore_sticky_posts' => 1, 'orderby' => 'post_date', 'order' => 'desc', 'numberposts' => $posts ) );

		ob_start();
		$count = 1;
		$date_format = get_option('date_format');
		foreach($latest as $post) :
			setup_postdata($post);
			if( $count++ % 2 ){
				$class = 'odd';
			} else {
				$class = 'even';
			}
		?>
			<li class="<?php echo $class; ?>">
				<?php if ($size <> 0){
					$imageArgs = array(
						'width' => $size,
						'height' => $size,
						'image_class' => 'thumbnail',
						'format' => 'array',
						'default_image' => self::getWidgetUrl() . 'default.png'
					);
					$postImage = pptwj_get_the_image($imageArgs);
				}
				?>
				<?php if( !empty( $postImage['src'] ) ):
					$css = "width: {$size}px; height: {$size}px;";
				?>
				<a class="post-thumb" href="<?php the_permalink(); ?>"><img src="<?php echo $postImage['src']; ?>" alt="<?php echo $postImage['alt']; ?>" width="<?php echo $postImage['width']; ?>" height="<?php echo $postImage['height']; ?>" style="<?php echo $css; ?>"/></a>
				<?php endif; ?>

				<a class="item-title" title="<?php the_title_attribute(); ?>" href="<?php the_permalink(); ?>"><?php the_title(); ?></a>

				<?php echo self::item_meta(get_the_time($date_format, $post)); ?>

				<div class="fix"></div>
			</li>
		<?php endforeach;
		$contents = ob_get_contents();
		ob_end_clean();
		return $contents;
	}

I am trying to make that to display all the articles excepting a category with id 12. Do you know where do i have to add something in my code ?

Thanks for your help!