设置Label，左右模糊效果

用到 CAGradientLayer 来作为 Label的mask

    CAGradientLayer *l = [CAGradientLayer layer];
    l.frame = self.titleView.bounds;
    l.colors = [NSArray arrayWithObjects:(id)[UIColor clearColor].CGColor, (id)[UIColor whiteColor].CGColor, (id)[UIColor clearColor].CGColor, nil];
    l.startPoint = CGPointMake(0.0f, 0.5f);
    l.endPoint = CGPointMake(1.0f, 0.5f);
    self.titleView.layer.mask = l;

设置左右模糊效果.png