Use of undeclared identifier in ViewController

Question

I know that its the kind that can be asked everyday, but the fact is that the answer can be different for every questions, and I didn't find any yet.

I am currently a real beginner in Objective C, and I am developing an app using the framework OpenCV.

I have been following this website for learning and then I got my problem.

I copied/pasted the 3 methods that are given in the website to convert cv::Mat to UIImage and UIImage to cv::Mat, but I can't use them :

My *.pch file :

#import <Availability.h>

#ifndef __IPHONE_5_0
#warning "This project uses features only available in iOS SDK 5.0 and later."
#endif

#ifdef __cplusplus
#import <opencv2/opencv.hpp>
#endif

#ifdef __OBJC__
#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#endif

My ViewController.hh file

#import <UIKit/UIKit.h>
@interface ViewController : UIViewController

- (cv::Mat)cvMatFromUIImage:(UIImage *)image;
- (cv::Mat)cvMatGrayFromUIImage:(UIImage *)image;
- (UIImage *)UIImageFromCVMat:(cv::Mat)cvMat;
@end

and my ViewController.mm file

#import "ViewController.hh"

@interface ViewController ()

@end


@implementation ViewController

- (cv::Mat)cvMatFromUIImage:(UIImage *)image
{
    @@@//what is given in the linked website
    return cvMat;
}

- (cv::Mat)cvMatGrayFromUIImage:(UIImage *)image
{
    @@@//what is given in the linked website
    return cvMat;
}

-(UIImage *)UIImageFromCVMat:(cv::Mat)cvMat
{
    @@@//what is given in the linked website    
    return finalImage;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    NSString* filename = [[NSBundle mainBundle] pathForResource:@"openCV" ofType:@"jpg"];
    UIImage *image = [UIImage imageWithContentsOfFile:filename];

    cv::Mat inputMat = cvMatFromUIImage(image);
    UIImage *newImage = UIImageFromCVMat(inputMat);

    self.view.backgroundColor = [UIColor colorWithPatternImage:newImage];
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"HelloWorld !" message:@"Welcome to OpenCV !" delegate:self cancelButtonTitle:@"Continue" otherButtonTitles:nil, nil];
    [alert show];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

@end

The 2 errors are on the lines that are alone in (void) viewDidLoad in the .mm file, it says that both cvMatFromUIImage and UIImageFromCVMat aren't declared.

It might be a stupid question, I guess that I missed something, but don't know what.

Please help me :)

Answer 1

I think you've defined your functions in Objective-C but are using the C standard for calling them... Change these:

cvMatFromUIImage(image)
UIImageFromCVMat(inputMat)

to

[self cvMatFromUIImage:image];
[self UIImageFromCVMat:inputMat];