PCR image refers to a raster graphics format associated with the OPTIKS graphics software for DOS, and its predecessor, PC Rockland Graphics Base (PCRGB). The software was developed by Keith P. Graham. The format is sometimes called PC Rockland ultra-squished data format.
PCR image files apparently start with bytes
'K' 'P' 'G' ?? ?? 0x10.
Compare to PCR font#Identification.