ios如何加载gif图片

ios如何加载gif图片

直接使用SDWebImage第三方库就可以了

这里主要使用了UIImage的类方法

+ (nullable UIImage *)animatedImageWithImages:(NSArray<UIImage *> *)images duration:(NSTimeInterval)duration NS_AVAILABLE_IOS(5_0);

需要两个参数,一个是一组图片资源,一个是动画执行时间,这个执行时间是所有帧执行的总时间.因此需要计算这两个参数.
图片的输入输出需要#import <ImageIO/ImageIO.h>这个头文件
计算上面两个参数,需要获取gif的图片资源文件,获取其相关属性.写了一个分类方法具体代码如下:

/**
 承载gif内容的image对象
 图片名称,一般不带后缀名
 @param gifName gif图片名称
 @return  承载gif内容的image对象
 */
+(UIImage *)imageNamedGifName:(NSString *)gifName{
    //1.找到文件获取文件数据
    if ([gifName hasSuffix:@".gif"]) {
        gifName = [gifName stringByReplacingOccurrencesOfString:@".gif" withString:@""];
    }
    NSURL *url = [[NSBundle mainBundle] URLForResource:gifName withExtension:@".gif"];
    NSData *data = [NSData dataWithContentsOfURL:url];
    if (!data) {
        return nil;
    }
    //2.获取文件资源 这里需要导入imageIO类
    CGImageSourceRef sourceRef = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);
    size_t count =  CGImageSourceGetCount(sourceRef);
    NSTimeInterval douration = 0;//存储gif动画总时间
    NSMutableArray *images = [NSMutableArray arrayWithCapacity:3];//储存的图片
    for (size_t i = 0; i < count; i++) {
        //获取每一张图片 并保存需要的信息
     CGImageRef imageRef =  CGImageSourceCreateImageAtIndex(sourceRef, i, NULL);
        if (imageRef) {
            [images addObject:[UIImage imageWithCGImage:imageRef]];
         NSDictionary *dict = (__bridge NSDictionary *) CGImageSourceCopyPropertiesAtIndex(sourceRef, i, NULL);
         NSDictionary *gifPorperty = dict[(__bridge NSString *)kCGImagePropertyGIFDictionary];
           NSNumber *unclampedDelayTime = gifPorperty[(__bridge NSString *)kCGImagePropertyGIFUnclampedDelayTime];
            float thisDelyTime = 0;
            if (unclampedDelayTime) {
                thisDelyTime = unclampedDelayTime.floatValue;
            }else{
                NSNumber *delyTime = gifPorperty[(__bridge NSString *)kCGImagePropertyGIFDelayTime];
                thisDelyTime = delyTime.floatValue;
            }
            //如果低于10ms 设置成100ms参考如下解释
            // 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 (thisDelyTime <= 0.001f) {
                thisDelyTime = 0.1f;
            }
            douration += thisDelyTime;
        }
        CGImageRelease(imageRef);
    }
    CFRelease(sourceRef);
    //获得最终图片
    return [UIImage animatedImageWithImages:images duration:douration];;
}