Improve SDWebImage library with support for a UIActivityIndicator and optional image transition. The transition animation is a simple fade-in.

UIImageView+Webcache_Animation.c

//
//  UIImageView+Webcache_Animation.m
//  Tubesmix
//
//  Created by Cherif YAYA on 17/03/13.
//  Copyright (c) 2013 Cherif YAYA. All rights reserved.
//

#import "UIImageView+Webcache_Animation.h"

@implementation UIImageView (Webcache_Animation)

-(void) setImageWithURL:(NSURL *)url usingActivityIndicatorStyle : (UIActivityIndicatorViewStyle) activityStyle animated:(BOOL)animated {
    
    [self setImageWithURL:url placeholderImage:nil usingActivityIndicatorStyle:activityStyle animated:animated];
}

-(void) setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholderImage usingActivityIndicatorStyle : (UIActivityIndicatorViewStyle) activityStyle animated:(BOOL)animated {
    
    __block UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:activityStyle];
    activityIndicator.hidesWhenStopped = YES;
    [self addSubview:activityIndicator];
    activityIndicator.frame = self.bounds;
    [activityIndicator startAnimating];
    
    __block UIImageView *weakSelf = self;
    [self setImageWithURL:url placeholderImage:placeholderImage
                     completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) {
                         [activityIndicator removeFromSuperview];
                         //show animation if needed
                         if (image && cacheType == SDImageCacheTypeNone && animated)
                         {
                             weakSelf.alpha = 0.0;
                             [UIView animateWithDuration:0.35f
                                              animations:^{
                                                  weakSelf.alpha = 1.0;
                                              }];
                         }
                     }];
}

@end

UIImageView+Webcache_Animation.h

#import "UIImageView+Webcache.h"

@interface UIImageView (Webcache_Animation)

/**
  * Set the imageView `image` with an `url`.
  * and put an activity indicator while downloading the.
  *
  * The downloand is asynchronous and cached. And the image display can be animated.
  *
  * @param url The url for the image.
  * @param activityStyle THe UIActivityIndicatorViewStyle to use
  * @param animated Whether the image display is animated or not
  */
-(void) setImageWithURL:(NSURL *)url usingActivityIndicatorStyle:(UIActivityIndicatorViewStyle)activityStyle animated:(BOOL)animated;


/**
 * Set the imageView `image` with an `url`.
 * and put an activity indicator while downloading the.
 *
 * The download is asynchronous and cached. And the image display can be animated.
 *
 * @param url The url for the image.
 * @param placeholderImage An optional image placeholder
 * @param activityStyle THe UIActivityIndicatorViewStyle to use
 * @param animated Whether the image display is animated or not
 */
-(void) setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholderImage usingActivityIndicatorStyle:(UIActivityIndicatorViewStyle)activityStyle animated:(BOOL)animated;

@end