Added DTAnimatedGIF implementation and Demo

Core/Source/iOS/DTAnimatedGIF/DTAnimatedGIF.h

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+//
+//  DTAnimatedGIF.h
+//  DTFoundation
+//
+//  Created by Oliver Drobnik on 7/2/14.
+//  Copyright (c) 2014 Cocoanetics. All rights reserved.
+//
+
+
+/**
+ Loads an animated GIF from file, compatible with UIImageView
+ */
+UIImage *DTAnimatedGIFFromFile(NSString *path);
+
+/**
+ Loads an animated GIF from data, compatible with UIImageView
+ */
+UIImage *DTAnimatedGIFFromData(NSData *data);

Core/Source/iOS/DTAnimatedGIF/DTAnimatedGIF.m

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+//
+//  DTAnimatedGIF.m
+//  DTFoundation
+//
+//  Created by Oliver Drobnik on 7/2/14.
+//  Copyright (c) 2014 Cocoanetics. All rights reserved.
+//
+
+#import "DTAnimatedGIF.h"
+#import <ImageIO/ImageIO.h>
+
+// returns the frame duration for a given image in 1/100th seconds
+// source: http://stackoverflow.com/questions/16964366/delaytime-or-unclampeddelaytime-for-gifs
+static NSUInteger DTAnimatedGIFFrameDurationForImageAtIndex(CGImageSourceRef source, NSUInteger index)
+{
+	NSUInteger frameDuration = 10;
+
+	NSDictionary *frameProperties = CFBridgingRelease(CGImageSourceCopyPropertiesAtIndex(source,index,nil));
+	NSDictionary *gifProperties = frameProperties[(NSString *)kCGImagePropertyGIFDictionary];
+
+	NSNumber *delayTimeUnclampedProp = gifProperties[(NSString *)kCGImagePropertyGIFUnclampedDelayTime];
+
+	if(delayTimeUnclampedProp)
+	{
+		frameDuration = [delayTimeUnclampedProp floatValue]*100;
+	}
+	else
+	{
+		NSNumber *delayTimeProp = gifProperties[(NSString *)kCGImagePropertyGIFDelayTime];
+
+		if(delayTimeProp)
+		{
+			frameDuration = [delayTimeProp floatValue]*100;
+		}
+	}
+
+	// Many annoying ads specify a 0 duration to make an image flash as quickly as possible.
+	// We follow Firefox's behavior and use a duration of 100 ms for any frames that specify
+	// a duration of <= 10 ms. See <rdar://problem/7689300> and <http://webkit.org/b/36082>
+	// for more information.
+
+	if (frameDuration < 1)
+	{
+		frameDuration = 10;
+	}
+
+	return frameDuration;
+}
+
+// returns the great common factor of two numbers
+static NSUInteger DTAnimatedGIFGreatestCommonFactor(NSUInteger num1, NSUInteger num2)
+{
+	NSUInteger t, remainder;
+
+	if (num1 < num2)
+	{
+		t = num1;
+		num1 = num2;
+		num2 = t;
+	}
+
+	remainder = num1 % num2;
+
+	if (!remainder)
+	{
+		return num2;
+	}
+	else
+	{
+		return DTAnimatedGIFGreatestCommonFactor(num2, remainder);
+	}
+}
+
+static UIImage *DTAnimatedGIFFromImageSource(CGImageSourceRef source)
+{
+	size_t const numImages = CGImageSourceGetCount(source);
+
+	NSMutableArray *frames = [NSMutableArray arrayWithCapacity:numImages];
+
+	// determine gretest common factor of all image durations
+	NSUInteger greatestCommonFactor = DTAnimatedGIFFrameDurationForImageAtIndex(source, 0);
+
+	for (NSUInteger i=1; i<numImages; i++)
+	{
+		NSUInteger centiSecs = DTAnimatedGIFFrameDurationForImageAtIndex(source, i);
+		greatestCommonFactor = DTAnimatedGIFGreatestCommonFactor(greatestCommonFactor, centiSecs);
+	}
+
+	// build array of images, duplicating as necessary
+	for (NSUInteger i=0; i<numImages; i++)
+	{
+		CGImageRef cgImage = CGImageSourceCreateImageAtIndex(source, i, NULL);
+		UIImage *frame = [UIImage imageWithCGImage:cgImage];
+
+		NSUInteger centiSecs = DTAnimatedGIFFrameDurationForImageAtIndex(source, i);
+		NSUInteger repeat = centiSecs/greatestCommonFactor;
+
+		for (NSUInteger j=0; j<repeat; j++)
+		{
+			[frames addObject:frame];
+		}
+
+		CGImageRelease(cgImage);
+	}
+
+	// create animated image from the array
+	NSTimeInterval totalDuration = [frames count] * greatestCommonFactor / 100.0;
+	return [UIImage animatedImageWithImages:frames duration:totalDuration];
+}
+
+UIImage *DTAnimatedGIFFromFile(NSString *path)
+{
+	NSURL *URL = [NSURL fileURLWithPath:path];
+	CGImageSourceRef source = CGImageSourceCreateWithURL((__bridge CFURLRef)(URL), NULL);
+	UIImage *image = DTAnimatedGIFFromImageSource(source);
+	CFRelease(source);
+
+	return image;
+}
+
+UIImage *DTAnimatedGIFFromData(NSData *data)
+{
+	CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)(data), NULL);
+	UIImage *image = DTAnimatedGIFFromImageSource(source);
+	CFRelease(source);
+
+	return image;
+}