Develop an Algorithm for Color Conversion and Mac Apps that use it

I need an algorithm for converting among different color spaces: Munsell, LAB, RGB, and CMYK. And three desktop apps based on it: (1) batch conversion of lists of colors in from one of those spaces to all the others; (2) an eyedropper that samples patches of pixels and converts the data to those four different spaces; and (3) an app that will count the pixels in a photo, analyze their color, convert that information to Munsell and round it to the nearest Munsell "chip", then report the results. Developing the algorithm for conversion to Munsell is the hard part.