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Chapters:
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<a href="Introduction.html">1: Introduction</a><br>
<a href="SimpleExample.html">2: Simple example</a><br>
<a href="InvokingGri.html">3: Invocation</a><br>
<a href="GettingMoreControl.html">4: Finer Control</a><br>
<a href="X-Y.html">5: X-Y Plots</a><br>
<a href="ContourPlots.html">6: Contour Plots</a><br>
<a href="Images.html">7: Image Plots</a><br>
<a href="Examples.html">8: Examples</a><br>
<a href="Commands.html">9: Gri Commands</a><br>
<a href="Programming.html">10: Programming</a><br>
<a href="Environment.html">11: Environment</a><br>
<a href="Emacs.html">12: Emacs Mode</a><br>
<a href="History.html">13: History</a><br>
<a href="Installation.html">14: Installation</a><br>
<a href="Bugs.html">15: Gri Bugs</a><br>
<a href="TestSuite.html">16: Test Suite</a><br>
<a href="Acknowledgments.html">17: Acknowledgments</a><br>
<a href="License.html">18: License</a><br>
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Indices:</br>
<a href="ConceptIndex.html"><i>Concepts</i></a><br>
<a href="CommandIndex.html"><i>Commands</i></a><br>
<a href="BuiltinIndex.html"><i>Variables</i></a><br>
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<h2>8.7: Drawing gray polygons</h2>
The following example shows how to draw polygons of a graylevel that is
read in. It also draws a bullet (within the polygon). See the help
lines at the start.
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`Draw Polygon And Bullet'
Draw a polygon of a given graylevel, with a bullet
(black dot) at an indicated location. The polygon
coordinates are read in by this command, as are
the graylevel and the location of the bullet.
<p>
Variables used:
.black.
.white.
<p>
Input data read:
<p>
line 1:
A code (which is ignored) and a graylevel
to draw the polygon with. The value for this
graylevel ranges from .black. (which codes
to black ink on the paper) to .white.
(which codes to blank paper).
<p>
line 2:
An (x,y) location for the bullet.
<p>
line 3:
Skipped.
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line 4-n:
Locations of vertices of polygon, ended with a blank line.
{
read .code. .graylevel. # Read line 1
read .x. .y. # Read line 2
skip # Skip line 3
read columns x y # Read a polygon
# Adjust .graylevel. to range between 0
# (for black ink) and 1 (for white paper),
# then set graylevel and draw polygon.
.graylevel. = {rpn .graylevel. \
.black. - .white. .black. - /}
set graylevel .graylevel.
draw curve filled
# Draw black bullet
set graylevel 0
draw symbol bullet at .x. .y.
# Clean up local storage.
delete .code.
delete .graylevel.
delete .x.
delete .y.
}
</font></PRE>
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