iOS7 iOS8 毛玻璃效果的分别实现

[_headBGIV sd_setImageWithURL:headIVURL
                        completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
                            if (IOS8_OR_LATER)
                            {
                                UIBlurEffect *blur = [UIBlurEffect effectWithStyle:UIBlurEffectStyleDark];
                                UIVisualEffectView *effectview = [[UIVisualEffectView alloc] initWithEffect:blur];
                                effectview.frame = _headBGIV.bounds;
                                [_headBGIV addSubview:effectview];
                            }
                            else
                            {
                                _headBGIV.image = [image applyDarkEffect];
                            }
                            
                            // 动画显示
                            NSString *aniType = kCATransitionFade;
                            CATransition *fadeAni = [CATransition animation];
                            fadeAni.duration = 0.68f;
                            fadeAni.type = aniType;
                            fadeAni.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
                            [[headView layer] addAnimation:fadeAni forKey:nil];
                        }];