如何获取xcassets中LaunchImage图片

NSDictionary * dic = @{@"320x480" : @"LaunchImage-700", @"320x568" : @"LaunchImage-700-568h", @"375x667" : @"LaunchImage-800-667h", @"414x736" : @"LaunchImage-800-Portrait-736h"};
 
NSString * key = [NSString stringWithFormat:@"%dx%d", (int)[UIScreen mainScreen].bounds.size.width, (int)[UIScreen mainScreen].bounds.size.height];
 
UIImage * launchImage = [UIImage imageNamed:dict[key]];