iOS UIImageView填充模式

图片等比例缩放之后显示问题但是填充模式设置了.gif UIImageView填充样式.gif
UIViewContentModeScaleToFill,
UIViewContentModeScaleAspectFit,
// contents scaled to fit with fixed aspect. remainder is transparent
UIViewContentModeScaleAspectFill,
// contents scaled to fill with fixed aspect. some portion of content may be clipped.
UIViewContentModeRedraw,
// redraw on bounds change (calls -setNeedsDisplay)
UIViewContentModeCenter,
// contents remain same size. positioned adjusted.
UIViewContentModeTop,
UIViewContentModeBottom,
UIViewContentModeLeft,
UIViewContentModeRight,
UIViewContentModeTopLeft,
UIViewContentModeTopRight,
UIViewContentModeBottomLeft,
UIViewContentModeBottomRight,