DreamPiggy

This is the GIF in browser behavior, but will break APNG and Animated WebP behavior in browser. You can check that both these set 0 by default to infinity loop...

you can also create an `YYImage` subclass to set that loopCount to 1 😄

UIButton's internal imageView is not a `YYAnimatedImageView` subclass. I think UIButton is suitable for small UI image, so the frame count and resolution is small enough for memory to load....

Create a subclass of `YYImage` and overrite `animatedImageLoopCount` to return 1. Then use the instance of this subclass to set `YYAnimatedImageView.image`.

Scale problem ? YYImage seems get the twice scale factor(looks SD is @1x but YY is @2x)

LGTM......But there are nobody can merge :)

use `YYImage *image = [[YYImageCache sharedCache] getImageForKey:sticker.url];`

不同ColorSpace的整个Bitmap的顺序是不同的，CGImage通过`CGBitmapInfo`来控制，比如字节序（大端，小端），RGBA的通道数（是否含有Alpha）等。YY的解码比较复杂，在内存中解码可以先使用不同的ColorSpace，减少内存开销。而渲染到屏幕上的时候可以换成iOS的CALayer渲染所需要的`CGColorSpaceCreateDeviceRGB`对应的BitmapInfo…… 不过说实话这个有点过于考虑性能了，一般的图片库很少用到……

Learn from my contribute to SDWebImage [Pull Request](https://github.com/rs/SDWebImage/pull/1987) about support Progressive Download for static WebP. It's not hard(to say, it's looks easy) to implement. But I focus on SDWebImage and...

SD 3.x use `+ animatedImageWithImages:duration:` and decode GIF to UIImage array to draw. But it sometimes has performance issue. YYImage use a abstract layer to save the infomation for each...