| starting point of dashed lines [message #65737] |
Sun, 22 March 2009 09:28  |
Jeremy Bailin
Messages: 618
Registered: April 2008
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Senior Member |
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Any sort of dashed and/or dotted linestyle (i.e. anything other than
linetsyle=0) has some natural "starting point" or phase. Is there a
way to manually reset it?
My specific problem is that I'm generating some plots in .png files
that are going to be stuck together as an animation, including a
dashed line that should be identical in each plot. However, it isn't -
at least, not when plotted to the Z buffer! Here is some code that
demonstrates this:
set_plot, 'z'
plot, [0,1], [-0.5,0.5]
erase
oplot, [0,1], [0,0], lines=2
write_png, 'test1.png', tvrd()
erase
oplot, [0,1], [0,0], lines=2
write_png, 'test2.png', tvrd()
If you compare the two .png files, you'll see that the dashing is
shifted slightly. However, if I do this with set_plot,'x' instead, it
works fine!
-Jeremy.
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| Re: starting point of dashed lines [message #65864 is a reply to message #65737] |
Tue, 24 March 2009 06:18  |
Jeremy Bailin
Messages: 618
Registered: April 2008
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Senior Member |
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On Mar 23, 1:32 pm, Paolo <pgri...@gmail.com> wrote:
> Ok,
>
> you should try:
>
> http://hea-www.cfa.harvard.edu/~pgrigis/idl_stuff/pg_dashedl ineoplot.pro
>
> This uses fcheck.pro from solarsoft:http://sohowww.nascom.nasa.gov/solarsoft/gen/idl/u til/fcheck.pro
>
> Here's an example.
> p1=[1,1] & p2=[5,3]
> plot,[0,0],xrange=[0,10],yrange=[0,7],/iso
> pg_dashedlineoplot,p1,p2,dashlen=0.05,spacelen=0.01,phase=0. 0
>
> This works only for straight line segments! Therefore,
> not extremly useful. Also the definition of the dash
> lengths may not be the most intuitive...
>
> Since this was not really built with wide distribution in mind,
> the usual caveats apply (use at your own risk etc.), but
> let us know if it is useful for you. I most certainly did not
> perform extensive tests.
>
> Ciao,
> Paolo
>
> Jeremy Bailin wrote:
>> On Mar 23, 10:22 am, Paolo <pgri...@gmail.com> wrote:
>>> Hi Jeremy,
>
>>> yes, this is one of the things I dislike about plot,
>>> that such details as the phase of dashes is totally
>>> out of control.
>
>>> In fact, at some point I wrote a little procedure to
>>> overplot with dashes of specified length and phase...
>>> I should still have it I believe, and I can dig it up for
>>> you if that would be useful...
>
>>> Ciao,
>>> Paolo
>
>>> Jeremy Bailin wrote:
>>>> On Mar 22, 12:28 pm, Jeremy Bailin <astroco...@gmail.com> wrote:
>>>> > Any sort of dashed and/or dotted linestyle (i.e. anything other than
>>>> > linetsyle=0) has some natural "starting point" or phase. Is there a
>>>> > way to manually reset it?
>
>>>> > My specific problem is that I'm generating some plots in .png files
>>>> > that are going to be stuck together as an animation, including a
>>>> > dashed line that should be identical in each plot. However, it isn't -
>>>> > at least, not when plotted to the Z buffer! Here is some code that
>>>> > demonstrates this:
>
>>>> > set_plot, 'z'
>>>> > plot, [0,1], [-0.5,0.5]
>>>> > erase
>>>> > oplot, [0,1], [0,0], lines=2
>>>> > write_png, 'test1.png', tvrd()
>>>> > erase
>>>> > oplot, [0,1], [0,0], lines=2
>>>> > write_png, 'test2.png', tvrd()
>
>>>> > If you compare the two .png files, you'll see that the dashing is
>>>> > shifted slightly. However, if I do this with set_plot,'x' instead, it
>>>> > works fine!
>
>>>> > -Jeremy.
>
>>>> Incidentally, the easiest way to see this is to omit the second
>>>> "erase" command in my example - then the actual size of the dashes
>>>> appears to get bigger as out-of-phase dashes get overplotted on top of
>>>> each other.
>
>>>> Anyone?
>
>>>> -Jeremy.
>
>> Would love it. I've worked around this particular issue today by using
>> a gray line instead, but I can easily see it coming up again.
>
>> What bugs me is that there must be *some* internal variable that is
>> telling IDL what phase to start at. So how can we get at it??
>
>> -Jeremy.
>
>
Great, thanks!
-Jeremy.
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