Error with homebrew + opencv + libpng

Question

On Mac OS Maverick I have installed OpenCV with a brew install opencv.

I created a simple program (copied from this tutorial). Compilation worked fine but when running the executable I get the following error:

dyld: Library not loaded: /usr/local/lib/libpng16.16.dylib
  Referenced from: /usr/local/lib/libopencv_highgui.2.4.dylib
  Reason: Incompatible library version: libopencv_highgui.2.4.dylib requires version 33.0.0 or later, but libpng16.16.dylib provides version 32.0.0
Trace/BPT trap: 5

I checked that libpngwas properly installed via brew install libpng and ran a brew upgrade to make sure everything was up-to-date.

Running locate libpng16.dylib returns:

/Applications/GIMP.app/Contents/Resources/lib/libpng16.16.dylib
/usr/local/Cellar/libpng/1.6.10/lib/libpng16.16.dylib
/usr/local/Cellar/libpng/1.6.12/lib/libpng16.16.dylib
/usr/local/Cellar/libpng/1.6.13/lib/libpng16.16.dylib
/usr/local/Cellar/libpng/1.6.15/lib/libpng16.16.dylib
/usr/local/lib/libpng16.16.dylib

Any idea?

Answer 1

The best solution is to fully uninstall libpng and re-install it:

$ sudo brew uninstall libpng
$ sudo rm '/usr/local/bin/libpng-config'
$ for i in `brew link --overwrite --dry-run libpng`; do sudo rm $i; done
$ sudo brew install libpng

If you need to install opencv:

$ sudo brew tap homebrew/science
$ sudo brew install opencv

Answer 2

Homebrew should ensure that you the correct dependencies install. However, it's possible that you have more than one version of libpng16 installed at different paths. Have a look in...

/usr/lib
/opt/local/lib

If you find any versions of the library in these locations then they may be causing the wrong one to be loaded when your program starts. As a quick fix you can try typing DYLD_LIBRARY_PATH=/usr/local/lib before your program name on the command line. In the longer term you may need to remove the conflicting versions altogether.