//UIIamge 转 NSData

UIIamge *image = [UIImage imageNamed:@"imageName.png"];

NSData *imageData = UIImagePNGRepresentation(image]);

//NSData 转 UIIamge

NSData *data;

UIImage *image = [UIImage imageWithData:data];

//JSON字符串 转 NSDictionary

/*

NSJSONReadingOptions:

NSJSONReadingMutableLeaves

NSJSONReadingMutableContainers

NSJSONReadingAllowFragments

*/

NSString *string = @"{\"userId\":1,\"userName\":\"username\",\"nickName\":\"nickname\"}";

NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];

NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:nil];