set size ratio -1
set xrange [0:300]
set yrange [0:300]
unset key
set label "plot with rgbimage" at sc 0.4,0.15 \
    font "Helvetica,18" tc rgb "#006666" front
set term pngcairo enh font "Times,10" size 480,360
set out "plot_rgbimage.png"
plot "mandrill.png" binary filetype=png w rgbimage