title: CI Filter to create Black & White image?
body: <p>I have a CIImage I need to convert from color to Black and White within my Cocoa / objective C program.  Peter H. previously pointed me to this link <a href="http://www.codingadventures.com/2008/06/threshold-filter-in-glsl/" rel="noreferrer">http://www.codingadventures.com/2008/06/threshold-filter-in-glsl/</a> as a potential solution ... but I am having trouble compiling the kernel routine there (see separate thread, if interested).  </p>
  
  <p>So I am wondering if one of the other built-in CIFilters will accomplish what I'm trying to do.  I don't want a grayscale image ... I want each pixel in the Result image to be either Black or White -- I just need to be able to tell the filter how to determine which pixels should become black and which should become white.  The "Threshold" filter in Photoshop does exactly this -- it lets me specify the "threshold" and then it uses this value to decide which pixels become white and which become black.  This is what I am trying to "replicate" via code in my Xcode project.</p>
  
  <p>Any ideas if one of the other built in filters can be used for this?  Thanks.</p>