UIViewContentModeScaleToFill:图片拉伸至填充整个UIImageView（图片可能会变形）     UIViewContentModeScaleAspectFit:按照原来的宽高比，图...

typedefNS_ENUM(NSInteger,UIViewContentMode){//图片拉伸填充至整个UIImageView(图片可能会变形),这也是默认的属性,如果什么都不设置就是它在起作用UIViewContentModeScaleToFill,//图片拉伸至完全显示在UIImageView里面为止(图片不...

scaleAspectFill:Theoptiontoscalethecontenttofillthesizeoftheview.Someportionofthecontentmaybeclippedtofilltheview’sbounds.保持宽高比，填满整个view scaleAspectF...

typedefNS_ENUM(NSInteger,UIViewContentMode){UIViewContentModeScaleToFill,UIViewContentModeScaleAspectFit,//contentsscaledtofitwithfixedaspect.remainderistranspa...