image,s,a,,,,image or image section to be plotted
z1,r,h,0,,,minimum intensity to be mapped (0 if zmin)
z2,r,h,0,,,maximum intensity to be mapped (0 if zmax)
nlevels,i,h,0,,,number of levels to be drawn (0 for default)
mapping_function,s,h,"linear",,,type of mapping 
contrast,r,h,0.25,,,positive or negative contrast [+/-1]?
perimeter,b,h,yes,,,draw perimeter around plot?
device,s,h,stdgraph,,,output device
title,s,h,"imtitle",,,optional title
preserve,b,h,yes,,,preserve aspect ratio when decreasing resolution?
xres,i,h,64,,,x resolution in pixels
yres,i,h,64,,,y resolution in pixels
vx1,r,h,0.,,,NDC viewport x1
vx2,r,h,0.,,,NDC viewport x2
vy1,r,h,0.,,,NDC viewport y1
vy2,r,h,0.,,,NDC viewport y2
fill,b,h,no,,,fill viewport regardless of device aspect ratio?
subsample,b,h,no,,,subsample (vs block average) to reduce resolution?
append,b,h,no,,,append to an old plot?