UIImage* pic =[UIImage imageNamed:@"image.png"];  NSData *pictureData = UIImageJPEGRepresentation(pic, 1.0); 或者使用NSData* pictureData =UIImagePNGRepresentation(pic);（二者看需求选取） NSString* pictureString =[pictureData base64Encoding];  转回来: 
UIImage* image =[UIImage imageWithData:[NSData  dataFromBase64EncodedString: pictureString]];