图片上加载阴影效果

        UIImageView *blowImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, CGRectGetMaxY(label.frame)  + 8,CGRectGetWidth(self.view.bounds), 240)];

//        //渐变图层

        UIView *view = [[UIView alloc]initWithFrame:blowImageView.bounds];

        

        CAGradientLayer *gradientLayer =  [CAGradientLayer layer];

        gradientLayer.frame = view.bounds;

        

//        //设置颜色

        [gradientLayer setColors:[NSArray arrayWithObjects:(id)[[UIColor clearColor] CGColor],(id)[[UIColor colorWithRed:0.2 green:0.2 blue:0.2 alpha:0.773922413793103] CGColor], nil]];

//

//        //每种颜色最亮的位置

        [gradientLayer setLocations:@[@0.5,@0.8]];

        //渐变的方向StartPoint－>EndPoint

        [gradientLayer setStartPoint:CGPointMake(0.5, 0)];

        [gradientLayer setEndPoint:CGPointMake(0.5, 1)];

        blowImageView.image = [UIImage imageNamed:imageArray[index]];

        [view.layer insertSublayer:gradientLayer atIndex:0];

        [view addSubview:label];

        [blowImageView addSubview:view];

        [self.scrollView addSubview:blowImageView];