1. A color space conversion method comprising: receiving a set of control lines in a first color space, each control line of the first set of control lines comprising a plurality of control points having predetermined values in a second color space; identifying a planar region among the set of control lines in the first color space, the planar region containing a plurality of target points to be interpolated from the first color space to the second color space; partitioning the planar region into at least a first area and a second area, target points in said second area corresponding to a different set of colorants from the second color space than target points in the first area; and applying an interpolation to the target points in the second area to determine corresponding values in the second color space based at least in part on the predetermined values of control points bounding the second area.