imagemagick monochrome convert in iPhone

I have an image in the iPhone that I need to convert to monochrome. The images are photographs of documents and I need as clean a conversion as I can get.

My first solution did a pixel for pixel compare with a threshold, and while it does the conversion fine, shadows can overwhelm the image.

My next trial is to use imagemagick, hoping that there are various noise reduction/despeckle filters that I can apply to clean the image up, which is what this guy is doing.

I have imagemagick running on the iPhone and can apply "MagickWand" methods with no problem. My issue is that I don't think there is one built in that will do what I want. So I turn to the ConvertImageCommand but am lost on how to actually use it.

So I am lookin开发者_StackOverflowg for any guidance or examples. Thanks!

---

It turns out what I've been looking for is Adaptive Thresholding in my conversion to monochrome.

Chris Greening has created an image processing library that handles this quite well.

So no imagemagick needed.