# set terminal pngcairo  font "arial,8" size 500, 300 
# set output 'circles.3.png'
unset border
unset key
set size ratio -1 1,1
set noxtics
set noytics
set title "Lena's key points" 
set rrange [ * : * ] noreverse nowriteback  # (currently [8.98847e+307:-8.98847e+307] )
set trange [ * : * ] noreverse nowriteback  # (currently [-5.00000:5.00000] )
set xrange [ * : * ] noreverse nowriteback  # (currently [-2.48960:512.085] )
set x2range [ * : * ] noreverse nowriteback  # (currently [-2.48960:512.085] )
set yrange [ * : * ] reverse nowriteback  # (currently [510.000:-2.00000] )
set y2range [ * : * ] noreverse nowriteback  # (currently [510.000:-2.00000] )
set cbrange [ * : * ] noreverse nowriteback  # (currently [0.00000:300.000] )
plot 'lena.rgb' binary array=128x128 dx=4 dy=4 format='%uchar' with rgbimage,      'lena-keypoints.bin' binary format='%double' with circles lc rgb "yellow"