NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *savedImagePath = [documentsDirectory stringByAppendingPathComponent:@"savedImage.png"];
//also be .jpg or another
NSData *imageData = UIImageJPEGRepresentation(resultImage,0.8);
[imageData writeToFile:savedImagePath atomically:NO];