Reputation: 452

Apple Mach-O Linker (Id) Error using OpenCV framework for iOS

Got an other problem with my opencv project on iOS.

So I have a small project written in Ojective C with 2 methods written in C++ :

My ViewController.hh file :

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

static UIImage* MatToUIImage(const cv::Mat& m);
static void UIImageToMat(const UIImage* image, cv::Mat& m);
@end

and my ViewController.mm file :

#import "ViewController.hh"

@interface ViewController ()

@end

@implementation ViewController

static UIImage* MatToUIImage(const cv::Mat& m) {
    CV_Assert(m.depth() == CV_8U);
    NSData *data = [NSData dataWithBytes:m.data length:m.elemSize()*m.total()];
    CGColorSpaceRef colorSpace = m.channels() == 1 ?
    CGColorSpaceCreateDeviceGray() : CGColorSpaceCreateDeviceRGB();
    CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
    // Creating CGImage from cv::Mat
    CGImageRef imageRef = CGImageCreate(m.cols, m.cols, m.elemSize1()*8, m.elemSize()*8,
                                        m.step[0], colorSpace, kCGImageAlphaNoneSkipLast|kCGBitmapByteOrderDefault,
                                        provider, NULL, false, kCGRenderingIntentDefault);
    UIImage *finalImage = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef); CGDataProviderRelease(provider);
    CGColorSpaceRelease(colorSpace); return finalImage;
}

static void UIImageToMat(const UIImage* image, cv::Mat& m) {
    CGColorSpaceRef colorSpace = CGImageGetColorSpace(image.CGImage);
    CGFloat cols = image.size.width, rows = image.size.height;
    m.create(rows, cols, CV_8UC4); // 8 bits per component, 4 channels
    CGContextRef contextRef = CGBitmapContextCreate(m.data, m.cols, m.rows, 8, m.step[0], colorSpace, kCGImageAlphaNoneSkipLast |kCGBitmapByteOrderDefault);
    CGContextDrawImage(contextRef, CGRectMake(0, 0, cols, rows), image.CGImage);
    CGContextRelease(contextRef); CGColorSpaceRelease(colorSpace);
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    NSString* filename = [[NSBundle mainBundle] pathForResource:@"cmc7" ofType:@"jpg"];
    UIImage *image = [UIImage imageWithContentsOfFile:filename];

    //cv::Mat inputMat = self.UIImageToMat(image);
    cv::Mat mat;
    UIImageToMat(image, mat);
    UIImage *newImage = MatToUIImage(mat);

    self.view.backgroundColor = [UIColor colorWithPatternImage:newImage];
}

I included my opencv framework this way :

#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

I precise that I have a similar project with the same includes, but with methods written in Objective C, and not in C++, and it works.

So here is my log error.

Undefined symbols for architecture i386:
  "cv::Exception::Exception(int, std::string const&, std::string const&, std::string const&, int)", referenced from:
      __ZL12MatToUIImageRKN2cv3MatE in ViewController.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

So what's the problem ? I really would prefer to have methods written in C++, because it's more common to use openCV using C++ language instead of Objective C.

Thank you very much.

Upvotes: 0