# set terminal png truecolor nocrop font arial 8 size 500,320 
# set output 'rgbalpha.1.png'
set border 31 front linetype -1 linecolor rgb "gold"  linewidth 1.000
set key title "Plot style rgbalpha" textcolor rgb "gold" 
set key screen 0.75, 0.75, 0 left bottom vertical Left noreverse enhanced autotitles nobox
set key noinvert samplen 1 spacing 1 width -7 height 0 
set object  1 rect from screen 0, 0, 0 to screen 1, 1, 0 behind lw 1.0 fc  rgb "gray10"  fillstyle   solid 1.00 noborder
set samples 128, 128
set size ratio 0.95 1,1
set rrange [ * : * ] noreverse nowriteback  # (currently [8.98847e+307:-8.98847e+307] )
set trange [ * : * ] noreverse nowriteback  # (currently [-5.00000:5.00000] )
set xrange [ 0.00000 : 130.000 ] noreverse nowriteback
set x2range [ * : * ] noreverse nowriteback  # (currently [0.00000:130.000] )
set yrange [ 0.00000 : 128.000 ] noreverse nowriteback
set y2range [ * : * ] noreverse nowriteback  # (currently [0.00000:128.000] )
set cbrange [ * : * ] noreverse nowriteback  # (currently [0.00000:255.000] )
set lmargin screen 0.1
set bmargin screen 0.1
set tmargin screen 0.9
plot 100.*(.4+sin(x/5.)/(x/5.)) lw 5 title 'solid line',      'lena.rgb' binary array=128x128 format="%uchar" flipy using 1:2:3:(2.*column(0))                 with rgbalpha title "Lena with linear\nalpha gradient"