matplotlib-users

[Matplotlib-users] ugly arrow with xpdf

[Friedrich H. <fri...@gm...>]

Hello,

when I create an arrow with

>>> from pylab import *
>>> subplot(111)
>>> arrow(.5, .5, -.05, .02, lw=5, width=.01)
>>> savefig('foo.pdf')

and view it with

  % xpdf foo.pdf

then I see on the startpoint an ugly pike. With gv and evince everything
is ok.

Any idea how to fix it in mpl? Because I dont want to switch to an other
viewer then xpdf.

Thanks,

  Friedrich

Re: [Matplotlib-users] ugly arrow with xpdf

[Jouni K. S. <jk...@ik...>]

Friedrich Hagedorn <fri...@gm...> writes:

>   % xpdf foo.pdf
>
> then I see on the startpoint an ugly pike. With gv and evince
> everything is ok.

Just to be sure about what the problem is, could you show us a
screenshot of the ugly rendering, and another of a better rendering in
another viewer? I think the list doesn't accept attachments, so it would
be best if you could put the files somewhere on the web and send a link
to the list or, failing that, send the screenshots to me by email.

Also, what exact version of xpdf are you using?

-- 
Jouni K. Seppänen
http://www.iki.fi/jks

Re: [Matplotlib-users] ugly arrow with xpdf

[Friedrich H. <fri...@gm...>]

On Mon, Jun 02, 2008 at 03:12:19PM +0300, Jouni K. Seppänen wrote:
> Friedrich Hagedorn <fri...@gm...> writes:
>
> >   % xpdf foo.pdf
> >
> > then I see on the startpoint an ugly pike. With gv and evince
> > everything is ok.
>
> Just to be sure about what the problem is, could you show us a
> screenshot of the ugly rendering, and another of a better rendering in
> another viewer? I think the list doesn't accept attachments, so it would
> be best if you could put the files somewhere on the web and send a link
> to the list or, failing that, send the screenshots to me by email.

I try it.

> Also, what exact version of xpdf are you using?

xpdf version 3.02

Thanks,

  Friedrich

Re: [Matplotlib-users] ugly arrow with xpdf

[Jouni K. S. <jk...@ik...>]

I can confirm this in at least version 0.91.3. The problem seems to be
caused by the midpoint of the stem being included in the path twice in a
row. The following patch removes the midpoint altogether and fixes the
rendering problem at least on my version of xpdf. I'm kind of swamped
right now, so I hope someone else can check whether this breaks any
other uses of arrows, or some other backend. (If this doesn't seem to
happen, please file a bug report in the tracker so it isn't forgotten.)
The patch is against the maintenance branch, but the trunk has
similar-looking code.

Index: lib/matplotlib/patches.py
===================================================================
--- lib/matplotlib/patches.py	(revision 5366)
+++ lib/matplotlib/patches.py	(working copy)
@@ -634,7 +634,13 @@
                 if shape == 'right':
                     coords = right_half_arrow
                 elif shape == 'full':
-                    coords=npy.concatenate([left_half_arrow,right_half_arrow[::-1]])
+                    # Concatenating the full paths caused the midpoint
+                    # of the stem to be included twice, which was
+                    # rendered badly by xpdf. Since the point is right
+                    # between the corners of the stem, we can drop it
+                    # from both halves.
+                    coords=npy.concatenate([left_half_arrow[:-1],
+                                            right_half_arrow[-2::-1]])
                 else:
                     raise ValueError, "Got unknown shape: %s" % shape
             cx = float(dx)/distance


-- 
Jouni K. Seppänen
http://www.iki.fi/jks

Re: [Matplotlib-users] ugly arrow with xpdf

[Friedrich H. <fri...@gm...>]

On Mon, Jun 02, 2008 at 11:17:44PM +0300, Jouni K. Seppänen wrote:
> I can confirm this in at least version 0.91.3. The problem seems to be
> caused by the midpoint of the stem being included in the path twice in a
> row. The following patch removes the midpoint altogether and fixes the
> rendering problem at least on my version of xpdf. I'm kind of swamped
> right now, so I hope someone else can check whether this breaks any
> other uses of arrows, or some other backend. (If this doesn't seem to
> happen, please file a bug report in the tracker so it isn't forgotten.)
> The patch is against the maintenance branch, but the trunk has
> similar-looking code.

Thank you very much. It works for me too.

> Index: lib/matplotlib/patches.py
> ===================================================================
> --- lib/matplotlib/patches.py (revision 5366)
> +++ lib/matplotlib/patches.py (working copy)
> @@ -634,7 +634,13 @@
>                  if shape == 'right':
>                      coords = right_half_arrow
>                  elif shape == 'full':
> -                    coords=npy.concatenate([left_half_arrow,right_half_arrow[::-1]])
> +                    # Concatenating the full paths caused the midpoint
> +                    # of the stem to be included twice, which was
> +                    # rendered badly by xpdf. Since the point is right
> +                    # between the corners of the stem, we can drop it
> +                    # from both halves.
> +                    coords=npy.concatenate([left_half_arrow[:-1],

for the most recent svn version: npy => np

> +                                            right_half_arrow[-2::-1]])
>                  else:
>                      raise ValueError, "Got unknown shape: %s" % shape
>              cx = float(dx)/distance

By,

  Friedrich

Re: [Matplotlib-users] ugly arrow with xpdf

[Jouni K. S. <jk...@ik...>]

I finally committed this fix.

-- 
Jouni K. Seppänen
http://www.iki.fi/jks