Question

I downloaded the OpenCV iOS framework from here and have it working fine with iOS 6, but on iOS 5.0, whenever I call:

self.videoCamera = [[CvVideoCamera alloc] initWithParentView:self.imageView];

from this tutorial, I get the following error message:

dyld: lazy symbol binding failed: Symbol not found: _objc_setProperty_nonatomic
  Referenced from: /var/mobile/Applications/8ADDFB67-97CE-4F6B-94B5-BD2548E0E6DD/MyApp.app/MyApp
  Expected in: /usr/lib/libobjc.A.dylib

dyld: Symbol not found: _objc_setProperty_nonatomic
  Referenced from: /var/mobile/Applications/8ADDFB67-97CE-4F6B-94B5-BD2548E0E6DD/MyApp.app/MyApp
Expected in: /usr/lib/libobjc.A.dylib

Is the latest version only for iOS 6? Is there an equivalent for iOS 5?

Answer 1

See this Q&A:

http://answers.opencv.org/question/4767/build-opencv-for-ios-5/

It seems that there are issues with latest source, and they suggest that you use the most recent pre-built framework (2.4.3).

Having said that, I have a version I built from current source last week which is running fine on ios6.0, 5.1 and 5.0 (see github projects here and here)

But when I try the video example you pointed to with this framework, I get the same error.

So it seems like it depends on exactly which feature of openCV you are trying to use….

update

I have just tried 2.4.3 and get the same error. Going back one version, 2.4.2, doesn’t help because <opencv2/highgui/cap_ios.h> is not present. This file declares the CvVideoCamera class and delegate protocol, so without it you won’t get anywhere with this example. Interestingly, cap_ios.h is an Objective-C class declaration, unlike the rest of openCV which is C++… so this particular feature might well only work with ios6

update2

OK I managed to get it running with a recent build of openCV from the latest source.

1 / Copy these pre-build source files into your project:

opencv/modules/highgui/src/

cap_ios_abstract_camera.mm
cap_ios_photo_camera.mm
cap_ios_video_camera.mm
cap_ios.h

2 / in the three .mm files change these lines:

#import "opencv2/highgui/cap_ios.h"
#include "precomp.hpp"

to:

#import "cap_ios.h"
// #include "precomp.hpp"

2 / In your viewController change

#import <opencv2/highgui/cap_ios.h>

to

#import "cap_ios.h"

That’s about it… possibly one or two other tweaks but i think that’s all it took to get it running under a deployment target of 5.1.