Getting Mono to play nice with ImageMagick on a Mac.

Mono doesn't ship with the greatest image manipulation library. Thankfully, there's a great, free library called ImageMagick that does the job and then some.

So, I started on a quest to interop some of the ImageMagick functionality with C# in Mono. But the first thing I had to do was install ImageMagick. And thus started my day of debugging.

I installed ImageMagick with MacPorts. It seemed simple enough:

sudo port install ImageMagick

And away went MacPorts, compiling and configuring and being an overall good little package manager.

MacPorts installed the ImageMagick libraries in opt/local/lib. The specific file I was interested in was /opt/local/lib/libMagickWand.dylib. First, you've got to create a Wand object, so I got out my interop pen and wrote some interop:

[DllImport("libMagickWand", EntryPoint = "MagickWandGenesis")]
static extern void WandGenesis();

The Mono runtime is supposed to resolve the "libMagickWand" path to the actual path of "libMagickWand.dylib" on the system. Unfortunately, there's a known bug in the process for Mac computers that's documented here, so you have to add a little configuration to your config files:

	<dllmap dll="libMagickWand" target="/opt/local/lib/libMagickWand.5.dylib" />

That should help point the runtime to the correct library. Ok. Let's invoke WandGenesis(); and start her up...

DllNotFoundException: libMagickWand. Ok. Maybe this isn't going to be that easy.

Nothing is impossible with stackoverflow, so I head over there and ask this question.

The advice I get is to run my executable with MONO_LOG_LEVEL set to debug. Let's try that.

export MONO_LOG_LEVEL=debug
mono ImageMagickWrapper.exe

And I see some interesting logs that point me to the root of my problem.

Mono: DllImport error loading library 'dlopen(/opt/local/lib/libMagickWand.5.dylib, 9):
no suitable image found.
Did find: /opt/local/lib/libMagickWand.5.dylib: mach-o, but wrong architecture'.

Wrong architecture, eh?

lipo -info libMagickWand.5.dylib
Non-fat file: libMagickWand.5.dylib is architecture: x86_64

Ok, so we've got a 64-bit version of ImageMagick. Now let's check out our Mono runtime.

mono -V
Mono JIT compiler version 2.10.5 (tarball Mon Aug 22 20:38:08 EDT 2011)
Copyright (C) 2002-2011 Novell, Inc, Xamarin, Inc and Contributors.
	TLS:           normal
	SIGSEGV:       normal
	Notification:  kqueue
	Architecture:  x86
	Disabled:      none
	Misc:          debugger softdebug 
	LLVM:          yes(2.9svn-mono)
	GC:            Included Boehm (with typed GC)

And there you have it. I've got a 32-bit installation of Mono and a 64-bit installation of ImageMagick. Now I'm off to try to figure out how to compile ImageMagick as 32-bit.


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