#2514 wgnuplot unable to plot dashed lines when setting terminal to jpeg

[Anonymous]

If you try

set term jpeg
set out "1.jpg"
plot sin(x) w l dt 2
unset out

it will plot with solid line, which is not dt 2 but dt 1; However, if you set term win for example, it will correctly plot with dashed lines type 2. I've tried dt3 and others, but it always plots with dt 1

[Ethan Merritt]

This is due to a missing upstream feature. The libgd graphics support library does not currently support dot/dash patterns. Therefore the gnuplot terminal types that depend on libgd (png jpeg gif sixel) do not currently support dashtype as a line property.

This is documented in the configuration and installation instructions, but yes it should probably be more clearly stated somewhere in the individual terminal "help" sections.

Suggested alternative: set term pngcairo

[Denis Gessert]

I just started looking into this, so I am by no means a libgd expert. Isn't gdImageSetStyle (or possibly gdImageSetBrush) enough to implement dashed lines. From what I have read gdImageSetStyle is the preferred option to draw dashed lines (since gdImageDashedLine was deprecated although it still seems to be working)

[Ethan Merritt]

That works adequately for purely horizontal or vertical lines, but fails badly for diagonal or curved lines. Don't believe what you read - try it.

[Denis Gessert]

I did actually try it but you are absolutely right: My test went as far as diagonal lines (which still works well by the way) but I would not know how to do curved lines without having to fall back to straight line dashes (which for most cases would not look acceptable). Thanks for the quick reply!