matplotlib-users

[Matplotlib-users] fill question

[Jeff W. <js...@fa...>]

How do I suppress drawing a line around the polygon when using fill?

I've tried  fill(x,y,'gray',linewidth=0), but I still get a little tiny 
line (which is especially noticeable when using the postscript backend).

-Jeff

-- 
Jeffrey S. Whitaker         Phone : (303)497-6313
NOAA/OAR/CDC  R/CDC1        FAX   : (303)497-6449
325 Broadway                Web   : http://www.cdc.noaa.gov/~jsw
Boulder, CO, USA 80305-3328 Office: Skaggs Research Cntr 1D-124

Re: [Matplotlib-users] fill question

[John H. <jdh...@ac...>]

>>>>> "Jeff" == Jeff Whitaker <js...@fa...> writes:

    Jeff> How do I suppress drawing a line around the polygon when
    Jeff> using fill?  I've tried fill(x,y,'gray',linewidth=0), but I
    Jeff> still get a little tiny line (which is especially noticeable
    Jeff> when using the postscript backend).

Just make the facecolor and edgecolor the same

  >>> fill(x,y, edgecolor='gray', facecolor='gray)

or whatever color you want them to be.  You can also use aliases

  >>> fill(x,y, ec='gray', fc='gray)

FYI, the new set/get introspection is designed to help you find these
things, by printing property names and the values they accept

In [3]: p, = fill(x,y)

In [4]: p
Out[4]: <matplotlib.patches.Polygon instance at 0x3b5ec60>

In [5]: set(p)
    alpha: float
    antialiased or aa: [True | False]
    clip_box: a matplotlib.transform.Bbox instance
    clip_on: [True | False]
    edgecolor or ec: any matplotlib color - see help(colors)
    facecolor or fc: any matplotlib color - see help(colors)
    figure: a matplotlib.figure.Figure instance
    fill: [True | False]
    label: any string
    linewidth or lw: float
    lod: [True | False]
    transform: a matplotlib.transform transformation instance
    visible: [True | False]
    zorder: any number


Hope this helps,
JDH

Re[2]: [Matplotlib-users] fill question

[Alan G I. <ai...@am...>]

>>>>>> "Jeff" == Jeff Whitaker <js...@fa...> writes:
>     Jeff> How do I suppress drawing a line around the polygon when
>     Jeff> using fill?  I've tried fill(x,y,'gray',linewidth=0), but I
>     Jeff> still get a little tiny line (which is especially noticeable
>     Jeff> when using the postscript backend).

On Tue, 28 Dec 2004, John Hunter apparently wrote:
> Just make the facecolor and edgecolor the same

I'll chime in here because I know someone is creating arrows
using polygons.  I have found that *any* width along the
edge is a problem for arrows: they must be *only* filled and
not stroked or they look like they point to the wrong point.
(Perhaps 0.3 point unscaled would not be a serious problem
for many uses, but remember there is a join at the tip!)
So: is it possible to fill a polygon without stroking the
edge (or to set the edge with to approximate 0)?

By way of comment: this was a real problem in gnuplot up to
version 3.8.  (I've been meaning to check whether it was
fixed in 4.0.)  The arrows were stroked as well as filled,
and they often looked very wrong.

fwiw,
Alan Isaac

Re: [Matplotlib-users] fill question

[Jeff W. <js...@fa...>]

John Hunter wrote:

>>>>>>"Jeff" == Jeff Whitaker <js...@fa...> writes:
>>>>>>            
>>>>>>
>
>    Jeff> How do I suppress drawing a line around the polygon when
>    Jeff> using fill?  I've tried fill(x,y,'gray',linewidth=0), but I
>    Jeff> still get a little tiny line (which is especially noticeable
>    Jeff> when using the postscript backend).
>
>Just make the facecolor and edgecolor the same
>
> 
>
John:  Thanks - I figured that one out myself about 5 minutes after I 
sent the message.

I'm currently working on a map plotting module.  I've added the ability 
to plot filled continents on various map projections, using the GSHHS 
coastline polygon dataset 
(http://www.soest.hawaii.edu/wessel/gshhs/gshhs.html).  This dataset 
provides polygon segments that define continental outlines.  However, 
before I post it here I'd like to also provide the capability to fill 
the 'wet' areas as well.  In order to do this I need to figure out how 
to fill the area between the polygons.   Looks like this module 
(http://www.dezentral.de/soft/Polygon/index.html) would do the trick, 
but it requires the generaly polygon clipping C library.   Do you have 
any suggestions?

Thanks for you help,

-Jeff

-- 
Jeffrey S. Whitaker         Phone  : (303)497-6313
Meteorologist               FAX    : (303)497-6449
NOAA/OAR/CDC  R/CDC1        Email  : Jef...@no...
325 Broadway                Web    : www.cdc.noaa.gov/~jsw
Boulder, CO, USA 80303-3328 Office : Skaggs Research Cntr 1D-124

Re: [Matplotlib-users] fill question

[John H. <jdh...@ac...>]

>>>>> "Jeff" == Jeff Whitaker <js...@fa...> writes:

    Jeff> I'm currently working on a map plotting module.  I've added
    Jeff> the ability to plot filled continents on various map
    Jeff> projections, using the GSHHS coastline polygon dataset
    Jeff> (http://www.soest.hawaii.edu/wessel/gshhs/gshhs.html).  This
    Jeff> dataset provides polygon segments that define continental
    Jeff> outlines.  However, before I post it here I'd like to also
    Jeff> provide the capability to fill the 'wet' areas as well.  In
    Jeff> order to do this I need to figure out how to fill the area
    Jeff> between the polygons.  Looks like this module
    Jeff> (http://www.dezentral.de/soft/Polygon/index.html) would do
    Jeff> the trick, but it requires the generaly polygon clipping C
    Jeff> library.  Do you have any suggestions?

agg actually includes a wrapper for gpc, as well as the gpc code
itself, but gpc is GPLd and I haven't included it in matplotlib for
that reason.  Agg separately implements a "scanline boolean algebra"
which I haven't studied in detail but which I understand basically
does the same thing: allow clipping to arbitrary polygons, and
supports boolean operations on polygons --
http://www.antigrain.com/demo/index.html#PAGE_DEMO_scanline_boolean

We have to expose the functionality such that it is available for use
by other backends, much as we use agg for image across backends.

If this is an area that you want to dive into, by all means.
Otherwise, it's on the list of things to do (I just added it to the
goals page in my tree, so it will appear on the site docs in the
not-too-distant-future.

JDH