Blur animation for Stasis' Cover Image View. This works for iOS8 only

gistfile1.m

//
//  STSCoverImageViewController.m
//  Stasis
//
//  Created by Cory D. Wiles on 6/5/14.
//  Copyright (c) 2014 Macspots. All rights reserved.
//

#import "STSCoverImageViewController.h"
#import "Profile.h"
#import "Profile+STSAdditions.h"
#import "STSCoverPhotoImageView.h"
#import "STSNavigationBar.h"

static CGFloat const STSSnapshotAnimationBlockDuration = 0.3f;

@interface STSCoverImageViewController ()

@property (nonatomic, strong) Profile *profile;
@property (nonatomic, strong, readwrite) STSCoverPhotoImageView *coverImageView;
@property (nonatomic, assign, getter=isViewBlurred) BOOL viewBlurred;
@property (nonatomic, strong) MSBlurredEffectView *blurredView;

@end

@implementation STSCoverImageViewController

@synthesize viewBlurred = _viewBlurred;

- (instancetype)initWithProfile:(Profile *)profile {

//  NSParameterAssert(profile != nil);
  
  self = [super init];
  
  if (self) {
    
    _profile     = profile;
    _viewBlurred = YES;
    
    if (_profile.coverPhoto) {

      UIImage *coverImage = [[UIImage alloc] initWithData:_profile.coverPhoto
                                                    scale:[UIScreen mainScreen].scale];

      _coverImageView = [[STSCoverPhotoImageView alloc] initWithImage:coverImage];
      
      UIColor *defaultNavigationBarColor = [_profile coverPhotoIsLight] ? [UIColor whiteColor] : [UIColor blackColor];
      NSDictionary *titleAttributes  = @{NSForegroundColorAttributeName : defaultNavigationBarColor};
      
      [[STSNavigationBar appearance] setTitleTextAttributes:titleAttributes];
      
      [UIApplication reloadUIAppearance];

    } else {
     
      _coverImageView = [[STSCoverPhotoImageView alloc] init];
    }
    
    _blurredView = [[MSBlurredEffectView alloc] initWithFrame:_coverImageView.frame
                                              blurEffectStyle:UIBlurEffectStyleLight];
    
    [_coverImageView addSubview:_blurredView.visualEffectView];
  }
  
  return self;
}

- (void)updateCoverPhotoWithImage:(UIImage *)image
                     successBlock:(void (^)(BOOL success, NSError *error))block {

  /**
   * @note
   * I might have to resave the profile
   */
  
  NSData *imageData = UIImagePNGRepresentation(image);
  CGFloat screenScale = [UIScreen mainScreen].scale;

  self.coverImageView.image = [[UIImage alloc] initWithData:imageData scale:screenScale];
  
  [self.profile updateCoverPhoto:imageData
                withSuccessBlock:^(NSData *imageData){
                  
                  if (block) {
                    block(YES, nil);
                  }
                }
                errorBlock:^(NSError *error){
                      
                  if (block) {
                    block(NO, error);
                  }
                }];
}

- (void)toggleBlurForCoverView {
  
  /**
   * Create snapshot then animate the alpha
   */
  
  UIView *snapshotView = [self.coverImageView snapshotViewAfterScreenUpdates:YES];
  
  /**
   * Block for removing snapshot view
   */
  
  dispatch_block_t snapshotToggleBlock = ^{
  
    [UIView animateWithDuration:STSSnapshotAnimationBlockDuration animations:^{
      
      snapshotView.alpha = 0.0f;
      
    } completion:^(BOOL finished){
      
      [snapshotView removeFromSuperview];
    }];
  };
  
  [self.coverImageView addSubview:snapshotView];
  
  if (self.isViewBlurred) {
    
    [self.blurredView.visualEffectView removeFromSuperview];
    
    snapshotToggleBlock();

  } else {

    [self.coverImageView insertSubview:self.blurredView.visualEffectView
                          belowSubview:snapshotView];

    snapshotToggleBlock();
  }
  
  self.viewBlurred = !self.viewBlurred;
}

#pragma mark - Accessors

- (BOOL)isViewBlurred {
  return _viewBlurred;
}

@end