图片上下居中对齐 按比例

function imgLoad(obj, width, height) {
	//定义要限制的图片宽高,这个宽高要同style里面定义的相同，小于限定高宽的图片不操作
	var image = $(obj);
	if (image.width() > width) {
	image.height(width / image.width() * image.height());
	image.width(width);
	}
	if (image.height() > height) {
	image.width(height / image.height() * image.width());
	image.height(height);
	}
	if (image.height() > 0 && image.height() < height) {
	image.css("paddingTop", (height - image.height()) / 2 + "px");
	image.css("paddingBottom", (height - image.height()) / 2 + "px");
	}
	}