UIImage 转换成 NSString注意事项

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]];