我有这个UIImage的扩展:extensionUIImage{funcresizeImage(newWidth:CGFloat,newHeight:CGFloat?=nil)->UIImage{letscale=newWidth/self.size.widthletfinalHeight=(newHeight==nil)?self.size.height*scale:newHeight!UIGraphicsBeginImageContextWithOptions(CGSize(width:newWidth,height:finalHeight),false,self.scale)se