png and dashed

[tv]

Is it possible to draw both color and dashed lines with the gd
terminals?
the lt -1 doesn't seem to do it as on the pdf term.

thanks a lot!

[Pete Gregory]

try lt 0

Hint. in gnuplot just run the command 'test' to see what the terminal
can do.

Pete.

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[iltommi]

On Jul 21, 5:00 pm, Pete Gregory <pgne...@bushlitt.org> wrote:
> try lt 0
>
> Hint.  in gnuplot just run the command 'test' to see what the terminal
> can do.

ok, using lt 0 gives a gray dashed line.
it didn't work for me because I also added the lw 3
here is a command that doesn't show the dashed line:

set term png enh
set out 'test.png'
plot x w l lt 0 lc rgb "black" lw 3
set out

is it the same for you?
maybe the space between a dash and the other gets filled by the larger
line, is it possible to increase the space between a dash and the
other?

thanks!

[sfeam]

iltommi wrote:

> On Jul 21, 5:00 pm, Pete Gregory <pgne...@bushlitt.org> wrote:
>> try lt 0
>>
>> Hint.  in gnuplot just run the command 'test' to see what the terminal
>> can do.
>
> ok, using lt 0 gives a gray dashed line.
> it didn't work for me because I also added the lw 3
> here is a command that doesn't show the dashed line:
>
> set term png enh
> set out 'test.png'
> plot x w l lt 0 lc rgb "black" lw 3
> set out
>
> is it the same for you?

No. As seen here in gnuplot version 4.2.5
lt 0 lc rgb "red" lw 3
produces a red dotted line with linewidth 1
(that is, it keeps the dots and the color but ignores the linewidth).

In the gnuplot cvs version, that same command
produces a thick red solid line. Backing off the thickness to
lt 0 lc rgb "red" lw 2
produces a less thick dotted line. So yes, the spacing between dots
can be filled up by a thick line. The terminal option
set term png ... dashlength N
is supposed to fix this, but it seems to be broken in the CVS version.

Note: It is possible that this behaviour also depends on the version
of libgd.

[iltommi]

I've touche at the gd.trm and made it work
at line 1534:
I've replaced
int psize = lw*lw*dashlength;

ssize = lw*lw*(spacelength + dashlength);
with
int psize = lw*dashlength;

ssize = lw*(spacelength + dashlength);

now it does something better, but it is still ugly:

set term png dashlength 0.5
set out 'test.png'
plot x w l lt 0 lw 4 lc rgb "black"
quit

probably some other variable must be adjusted.

Thanks!

[iltommi]

very ugly :-)

trying to plot a parabola, it seems that the driver can only plot
horizontal or vertical lines.

set term png dashlength 1
set out 'test.png'
plot x*x w l lt 0 lw 10 lc rgb "black"
quit

[sfeam]

> very ugly :-)
>
> trying to plot a parabola, it seems that the driver can only plot
> horizontal or vertical lines.

Unfortunately, that is a limitation of the gd graphics library.
It only draws reasonable dot/dash patternd for horizontal or vertical lines.

That's why gnuplot only provide it for linetype 0, which is normally used
only to draw the horizontal/vertical grid.

Perhaps some future version of libgd will provide a more useful option.
Or you could use the cairo-based png terminal driver instead.

[iltommi]

On 23 juil, 02:04, sfeam <sf...@users.sourceforge.net> wrote:
> > very ugly :-)
>
> > trying to plot a parabola, it seems that the driver can only plot
> > horizontal or vertical lines.
>
> Unfortunately, that is a limitation of the gd graphics library.
> It only draws reasonable dot/dash patternd for horizontal or vertical lines.

ok, that explains it!

> Perhaps some future version of libgd will provide a more useful option.
> Or you could use the cairo-based png terminal driver instead.

that'a almost impossible, tha machine I'm running on is quite old and
I don't have access to the system, cairo depends on a bunch of stuff
that it would be a nightmare to recompile everything!
at home I have an osx and (correct me if I'm wrong) it's impossible to
have cairo.

Not such a big problem however.

Thanks again