1. A method for converting a full color image to a highlight color image for output on an image output terminal, the method comprising: inputting a full color multi-bit image, wherein the full color image contains a plurality of pixel blocks; analyzing the inputted image on a block-by-block basis to determine whether each pixel block should be rendered in highlight color or non-highlight color; assigning each pixel block as one of highlight color and non-highlight color based on the analysis; separately processing assigned highlight color pixel blocks as a first image plane and assigned non-highlight color pixel blocks as a second image plane; combining the image planes to form an output file containing a highlight color image; and outputting the output file containing the highlight color image to an image output terminal.