       RE: Color Fill areas in 2D graphic

• To: mathgroup at smc.vnet.net
• Subject: [mg23387] RE: [mg23354] Color Fill areas in 2D graphic
• From: "David Park" <djmp at earthlink.net>
• Date: Fri, 5 May 2000 02:07:22 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```
>
> Hi,
> I want combine several ParametricPlot Images. After this is done, how
> can I fill areas within the image with a specific color ?
> thanks
> Roland Pabel
>

Hi Roland,

If you wish to try out my DrawingPaper routines, which are available at my
web site below, then the attached Mathematica notebook, ColoredArea.nb,
shows how to fill in areas with color. (MathGroup readers may contact me for
a copy of the notebook.)

If you have a closed curve defined by a parametric expression, then all you
have to do is convert the Line primitive to a Polygon primitive and supply a
color.

If the area is defined by the combination of several parametric arcs, then
DrawingPaper has a routine, StitchLineSegments which will stitch the arcs
together into one line which can then be converted to a Polygon.

Of course, the standard way to color the area between two curves is to use
FilledPlot, but this requires the first curve to always be above the second
curve. Sometimes this does not happen in the x-y plane but does happen in a
different coordinate system. In those cases the DrawingPaper routine
DrawingTransform can convert a FilledPlot back to x-y coordinates. For
example, the area outside a unit circle but inside a cardioid can be filled
with FilledPlot in a theta-r representation and then transformed to a x-y
representation.

The notebook has examples of coloring in a tilted ellipse, coloring in the
area bounded by two intersecting parabolas with their axes in the y and -y
direction, and the circle-cardioid example mentioned above.

The packages you will need for the notebook from my web site are
DrawingPaper.m and FilledDrawing.m. The packages should be put in the
AddOns/ExtraPackages/Graphics folder. There are also other Drawing packages
and a tutorial.

David Park

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David Park
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site. It \
should be placed in the AddOns/ExtraPackages/Graphics directory. It can
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be used just like the standard packages. Here is a click-on link to the
web \
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Here are two parabolas with their axes in the y and -y directions. (If
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So here we assemble our curve by drawing the two line segments
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Now it is a simple matter to draw the colored area and outline it in
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```

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