图片---播放gif图片

转载自:http://www.cnblogs.com/smileEvday/archive/2013/03/28/Gif.html

          三种方式显示GIF图片

播放gif图片通常会有四种方式

用UIWebView

    NSString *path = [[NSBundle mainBundle] pathForResource:@"run" ofType:@"gif"];    NSData *gifData = [NSData dataWithContentsOfFile:path];    UIWebView *webView = [[UIWebView alloc] initWithFrame:CGRectMake(0, 120, 100, 100)];    webView.backgroundColor = [UIColor <span style="font-family: Arial, Helvetica, sans-serif;">clearColor</span>];    webView.scalesPageToFit = YES;    [webView loadData:gifData MIMEType:@"image/gif" textEncodingName:nil baseURL:nil];    [self.view addSubview:webView];

要注意的点

这个webview可以设置透明： [webView setBackgroundColor:[UIColor clearColor]]; [webView setOpaque:NO];这样就不会出现白的底色，当然，前提是gif的每个桢图也是背景透明的。

webview需要将scrollview的滚动功能禁用，不然- -gif 是可以滚动的

优缺点

缺点: UIWebView的内存问题
优点: webview加载的gif会保持原有的桢速

用UIImageView的animationImages

    UIImageView *gifImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 240, 100, 100)];    NSArray *gifArray = [NSArray arrayWithObjects:[UIImage imageNamed:@"1"],                         [UIImage imageNamed:@"2"],                         [UIImage imageNamed:@"3"],                         nil];    gifImageView.animationImages = gifArray; //动画图片数组    gifImageView.animationDuration = 5; //执行一次完整动画所需的时长    gifImageView.animationRepeatCount = 999;  //动画重复次数    [gifImageView startAnimating];    [self.view addSubview:gifImageView];

缺点

只能保持相同的帧速

用GifView

- (id)initWithFrame:(CGRect)frame data:(NSData *)_data{        self = [super initWithFrame:frame];    if (self) {        // 得到图片的一些属性 这个可有可无gifProperties = [[NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:0] forKey:(NSString *)kCGImagePropertyGIFLoopCount] forKey:(NSString *)kCGImagePropertyGIFDictionary] retain];        //gif = CGImageSourceCreateWithURL((CFURLRef)[NSURL fileURLWithPath:_filePath], (CFDictionaryRef)gifProperties);        // 得到gif图片        gif = CGImageSourceCreateWithData((CFDataRef)_data, (CFDictionaryRef)gifProperties);        // 有多少张count =CGImageSourceGetCount(gif);timer = [NSTimer scheduledTimerWithTimeInterval:0.12 target:self selector:@selector(play) userInfo:nil repeats:YES];[timer fire];    }    return self;}-(void)play{index ++;index = index%count;CGImageRef ref = CGImageSourceCreateImageAtIndex(gif, index, (CFDictionaryRef)gifProperties);self.layer.contents = (id)ref;    CFRelease(ref);}

缺点

只能保持相同的帧速

用ImageIO来处理

我们知道Gif是由一阵阵画面组成的，而且每一帧画面播放的时常可能会不相等，观察上面两个例子，发现他们都没有对Gif中每一帧的显示时常做处理，这样的结果就是整个Gif中每一帧画面都是以固定的速度向前播放，很显然这并不总会符合需求。

于是smileEvday写一个解析Gif的工具类，解决每一帧画面并遵循每一帧所对应的显示时间进行播放。

　　程序的思路如下：

　　1、首先使用ImageIO库中的CGImageSource加载Gif文件。

　　2、通过CGImageSource获取到Gif文件中的总的帧数，以及每一帧的显示时间。

/* * @brief resolving gif information */void getFrameInfo(CFURLRef url, NSMutableArray *frames, NSMutableArray *delayTimes, CGFloat *totalTime,CGFloat *gifWidth, CGFloat *gifHeight){    CGImageSourceRef gifSource = CGImageSourceCreateWithURL(url, NULL);        // get frame count    size_t frameCount = CGImageSourceGetCount(gifSource);    for (size_t i = 0; i < frameCount; ++i) {        // get each frame        CGImageRef frame = CGImageSourceCreateImageAtIndex(gifSource, i, NULL);        [frames addObject:(id)frame];        CGImageRelease(frame);                // get gif info with each frame        NSDictionary *dict = (NSDictionary*)CGImageSourceCopyPropertiesAtIndex(gifSource, i, NULL);        NSLog(@"kCGImagePropertyGIFDictionary %@", [dict valueForKey:(NSString*)kCGImagePropertyGIFDictionary]);                // get gif size        if (gifWidth != NULL && gifHeight != NULL) {            *gifWidth = [[dict valueForKey:(NSString*)kCGImagePropertyPixelWidth] floatValue];            *gifHeight = [[dict valueForKey:(NSString*)kCGImagePropertyPixelHeight] floatValue];        }                // kCGImagePropertyGIFDictionary中kCGImagePropertyGIFDelayTime，kCGImagePropertyGIFUnclampedDelayTime值是一样的        NSDictionary *gifDict = [dict valueForKey:(NSString*)kCGImagePropertyGIFDictionary];        [delayTimes addObject:[gifDict valueForKey:(NSString*)kCGImagePropertyGIFDelayTime]];                if (totalTime) {            *totalTime = *totalTime + [[gifDict valueForKey:(NSString*)kCGImagePropertyGIFDelayTime] floatValue];        }                CFRelease(dict);    }        if (gifSource) {        CFRelease(gifSource);    }}

　　3、通过CAKeyframeAnimation来完成Gif动画的播放。

 CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"contents"];        NSMutableArray *times = [NSMutableArray arrayWithCapacity:3];    CGFloat currentTime = 0;    int count = _frameDelayTimes.count;    for (int i = 0; i < count; ++i) {        [times addObject:[NSNumber numberWithFloat:(currentTime / _totalTime)]];        currentTime += [[_frameDelayTimes objectAtIndex:i] floatValue];    }    [animation setKeyTimes:times];        NSMutableArray *images = [NSMutableArray arrayWithCapacity:3];    for (int i = 0; i < count; ++i) {        [images addObject:[_frames objectAtIndex:i]];    }        [animation setValues:images];    [animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]];    animation.duration = _totalTime;    animation.delegate = self;    animation.repeatCount = 5;        [self.layer addAnimation:animation forKey:@"gifAnimation"];