This converts an image to CPC MODE 0:
*Maximize saturation ('''Colors > Hue-Saturation'''; the CPC palette is very saturated, so this will give a better result)*'''Image > Scale image Image''' to 320xXX (proportional scaling)
*Then scale to 160xXX (non-proportional scaling)
*'''Colors > Posterize ''' with a setting of 3 levels
*Convert to CPC palette ('''Image > Mode > Indexed''', select '''Use custom palette''' and point to the CPC color palette file[http://www.cpctech.org.uk/download/gimp.zip]. Also select '''Remove unused colors''')
*Check '''Image > Image Properties''' for the number of colors used