用UImage承载Gif图片

1.首先，添加UIImage的扩展到工程中：
.h

#import <UIKit/UIKit.h>

@interface UIImage (GIF)

+ (UIImage *)sd_animatedGIFNamed:(NSString *)name;

+ (UIImage *)sd_animatedGIFWithData:(NSData *)data;

- (UIImage *)sd_animatedImageByScalingAndCroppingToSize:(CGSize)size;

@end

.m

#import "UIImage+GIF.h"
#import <ImageIO/ImageIO.h>

@implementation UIImage (GIF)

+ (UIImage *)sd_animatedGIFWithData:(NSData *)data {
    if (!data) {
        return nil;
    }

    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);

    size_t count = CGImageSourceGetCount(source);

    UIImage *animatedImage;

    if (count <= 1) {
        animatedImage = [[UIImage alloc] initWithData:data];
    }
    else {
        NSMutableArray *images = [NSMutableArray array];

        NSTimeInterval duration = 0.0f;

        for (size_t i = 0; i < count; i++) {
            CGImageRef image = CGImageSourceCreateImageAtIndex(source, i, NULL);

            duration += [self sd_frameDurationAtIndex:i source:source];

            [images addObject:[UIImage imageWithCGImage:image scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp]];

            CGImageRelease(image);
        }

        if (!duration) {
            duration = (1.0f / 10.0f) * count;
        }

        animatedImage = [UIImage animatedImageWithImages:images duration:duration];
    }

    CFRelease(source);

    return animatedImage;
}

+ (float)sd_frameDurationAtIndex:(NSUInteger)index source:(CGImageSourceRef)source {
    float frameDuration = 0.1f;
    CFDictionaryRef cfFrameProperties = CGImageSourceCopyPropertiesAtIndex(source, index, nil);
    NSDictionary *frameProperties = (__bridge NSDictionary *)cfFrameProperties;
    NSDictionary *gifProperties = frameProperties[(NSString *)kCGImagePropertyGIFDictionary];

    NSNumber *delayTimeUnclampedProp = gifProperties[(NSString *)kCGImagePropertyGIFUnclampedDelayTime];
    if (delayTimeUnclampedProp) {
        frameDuration = [delayTimeUnclampedProp floatValue];
    }
    else {

        NSNumber *delayTimeProp = gifProperties[(NSString *)kCGImagePropertyGIFDelayTime];
        if (delayTimeProp) {
            frameDuration = [delayTimeProp floatValue];
        }
    }

    // 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 < 0.011f) {
        frameDuration = 0.100f;
    }

    CFRelease(cfFrameProperties);
    return frameDuration;
}

+ (UIImage *)sd_animatedGIFNamed:(NSString *)name {
    CGFloat scale = [UIScreen mainScreen].scale;

    if (scale > 1.0f) {
        NSString *retinaPath = [[NSBundle mainBundle] pathForResource:[name stringByAppendingString:@"@2x"] ofType:@"gif"];

        NSData *data = [NSData dataWithContentsOfFile:retinaPath];

        if (data) {
            return [UIImage sd_animatedGIFWithData:data];
        }

        NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:@"gif"];

        data = [NSData dataWithContentsOfFile:path];

        if (data) {
            return [UIImage sd_animatedGIFWithData:data];
        }

        return [UIImage imageNamed:name];
    }
    else {
        NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:@"gif"];

        NSData *data = [NSData dataWithContentsOfFile:path];

        if (data) {
            return [UIImage sd_animatedGIFWithData:data];
        }

        return [UIImage imageNamed:name];
    }
}

- (UIImage *)sd_animatedImageByScalingAndCroppingToSize:(CGSize)size {
    if (CGSizeEqualToSize(self.size, size) || CGSizeEqualToSize(size, CGSizeZero)) {
        return self;
    }

    CGSize scaledSize = size;
    CGPoint thumbnailPoint = CGPointZero;

    CGFloat widthFactor = size.width / self.size.width;
    CGFloat heightFactor = size.height / self.size.height;
    CGFloat scaleFactor = (widthFactor > heightFactor) ? widthFactor : heightFactor;
    scaledSize.width = self.size.width * scaleFactor;
    scaledSize.height = self.size.height * scaleFactor;

    if (widthFactor > heightFactor) {
        thumbnailPoint.y = (size.height - scaledSize.height) * 0.5;
    }
    else if (widthFactor < heightFactor) {
        thumbnailPoint.x = (size.width - scaledSize.width) * 0.5;
    }

    NSMutableArray *scaledImages = [NSMutableArray array];

    UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);

    for (UIImage *image in self.images) {
        [image drawInRect:CGRectMake(thumbnailPoint.x, thumbnailPoint.y, scaledSize.width, scaledSize.height)];
        UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

        [scaledImages addObject:newImage];
    }

    UIGraphicsEndImageContext();

    return [UIImage animatedImageWithImages:scaledImages duration:self.duration];
}

@end

2.引入 "UIImage+GIF.h"扩展，调用上面相应的初始化方法，用UIImageView去加载展示即可。

3.示例，用于App启动动画(亦可制作其他动画效果)：

LaunchAnimationViewController.m

#import "LaunchAnimationViewController.h"
#import <UIImage+GIF.h>
#import "MainViewoController.h"

@interface LaunchAnimationViewController ()

@end

@implementation LaunchAnimationViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    
    UIImageView *launchAnimationView = [[UIImageView alloc] init];
    // frame可根据图片大小设定
    launchAnimationView.frame = self.view.bounds;
    // 创建gifImage,传入Gif图片名即可
    UIImage *gifImage = [UIImage sd_animatedGIFNamed:@"gifName"];
    launchAnimationView.image = gifImage;
    [self.view addSubview:launchAnimationView];
    
    // 执行隐藏动画，在动画完成后切换主界面
    [UIView animateWithDuration:0.3 delay:1.6 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
        launchAnimationView.alpha = 0;
    } completion:^(BOOL finished) {
        UIWindow *window = [UIApplication sharedApplication].keyWindow;
        window.rootViewController = [[MainViewoController alloc] init];
    }];
}

@end