Tells the color management system to preserve black (k) during
cmyk to cmyk transforms.
Normal cmyk to cmyk transforms first convert cmyk to device
independent XYZ using the source profile, then from XYZ to cmyk
using the destination profile. Since cmyk is an overdetermined
colorspace, an XYZ intermediate value can be represented by any
number of cmyk values. Setting 'preserveK' to 'true' tries to
preserve the 'K' value from source to destination.