I'm trying to plot a discrete brownian path in gnuplot, which involves a lot of overlaping lines. This is how it's displayed in the qt terminal (I have generated the image with a screenshot):

[![brownian path](https://i.stack.imgur.com/BLW6w.png)](https://i.stack.imgur.com/BLW6w.png)

Notice how the overlapping lines get colored in a stronger color, which is beautiful.

If I export it in png, with 

```
set term pngcairo size 1366,768 enhanced

```

I obtain this:

[![brownian path (png)](https://i.stack.imgur.com/3aIm7.png)](https://i.stack.imgur.com/3aIm7.png)

All the lines have the same intensity. Setting `transparent` doesn't help, either.

The same happens with this MWE:

```
set term pngcairo size 1366,768 background '#000000' enhanced
set output "image.png"
unset key
set border 0
unset xtics
unset ytics

set samples 1e6
set xrange [0:0.1]
p sin(1/x) w l lw 0.3
set output

```

[![mwe](https://i.stack.imgur.com/SLVwc.png)](https://i.stack.imgur.com/SLVwc.png)

I'm running `gnuplot -d` each time so my local config does not get loaded. How should I export the plot to obtain the same effect as in the GUI?