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<A HREF="toc.html">Contents</A>
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<A HREF="102Creatingasimplecanvas.html">Previous</A>
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<HR NOSHADE>
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<H2><A NAME="10_3">10.3 Adding lines and rectangles to a canvas</A></H2>
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<P> A canvas also makes a good background for using standard graphic
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primitives, for example circles and lines. What you first have to
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remember is that you are (so far) working with absolute screen
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coordinates and secondly all drawing primitives are found in the <A href="../ref/Image.html#_C_IMAGE">
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Image Class</A> accessible as a property of the Graph class. So for
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example to draw a line between coordinate (0,0) and (100,100) you would
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have to add the line<DIV class="phpscript"><CODE><FONT color="#000000">
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<FONT color="#0000BB"> $graph</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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Line</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">0</FONT><FONT
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color="#007700">,</FONT><FONT color="#0000BB">0</FONT><FONT color="#007700">
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,</FONT><FONT color="#0000BB">100</FONT><FONT color="#007700">,</FONT><FONT
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color="#0000BB">100</FONT><FONT color="#007700">);</FONT><FONT color="#0000BB">
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</FONT></FONT></CODE></DIV></P>
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<P></P>
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<P> To your code. The following example shows some of the graphic
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primitives you have access to in the Image class<DIV class="phpscript">
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(File: canvasex02.php)
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<BR><CODE><FONT color="#000000"> <FONT color="#0000BB"><?php
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<BR></FONT><FONT color="#FF8000">
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// $Id: canvasex02.php,v 1.1 2002/08/27 20:08:57 aditus Exp $
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<BR></FONT><FONT color="#007700">include </FONT><FONT color="#DD0000">
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"../jpgraph.php"</FONT><FONT color="#007700">;
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<BR>include </FONT><FONT color="#DD0000">"../jpgraph_canvas.php"</FONT><FONT
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color="#007700">;
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<BR>
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<BR></FONT><FONT color="#FF8000">// Setup a basic canvas we can work
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<BR></FONT><FONT color="#0000BB">$g </FONT><FONT color="#007700">= new </FONT><FONT
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color="#0000BB">CanvasGraph</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
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400</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">200</FONT><FONT
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color="#007700">,</FONT><FONT color="#DD0000">'auto'</FONT><FONT color="#007700">
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);
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">SetMargin</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
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5</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">11</FONT><FONT
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color="#007700">,</FONT><FONT color="#0000BB">6</FONT><FONT color="#007700">
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,</FONT><FONT color="#0000BB">11</FONT><FONT color="#007700">);
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">SetShadow</FONT><FONT color="#007700">();
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">SetMarginColor</FONT><FONT color="#007700">(</FONT><FONT color="#DD0000">
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"teal"</FONT><FONT color="#007700">);
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<BR>
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<BR></FONT><FONT color="#FF8000">
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// We need to stroke the plotarea and margin before we add the
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<BR>// text since we otherwise would overwrite the text.
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">InitFrame</FONT><FONT color="#007700">();
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<BR>
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<BR></FONT><FONT color="#FF8000">// Add a black line
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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SetColor</FONT><FONT color="#007700">(</FONT><FONT color="#DD0000">
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'black'</FONT><FONT color="#007700">);
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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Line</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">0</FONT><FONT
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color="#007700">,</FONT><FONT color="#0000BB">0</FONT><FONT color="#007700">
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,</FONT><FONT color="#0000BB">100</FONT><FONT color="#007700">,</FONT><FONT
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color="#0000BB">100</FONT><FONT color="#007700">);
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<BR>
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<BR></FONT><FONT color="#FF8000">// .. and a circle (x,y,diameter)
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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Circle</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">100</FONT><FONT
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color="#007700">,</FONT><FONT color="#0000BB">100</FONT><FONT color="#007700">
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,</FONT><FONT color="#0000BB">50</FONT><FONT color="#007700">);
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<BR>
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<BR></FONT><FONT color="#FF8000">
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// .. and a filled circle (x,y,diameter)
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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SetColor</FONT><FONT color="#007700">(</FONT><FONT color="#DD0000">'red'</FONT><FONT
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color="#007700">);
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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FilledCircle</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
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200</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">100</FONT><FONT
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color="#007700">,</FONT><FONT color="#0000BB">50</FONT><FONT color="#007700">
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);
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<BR>
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<BR></FONT><FONT color="#FF8000">// .. add a rectangle
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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SetColor</FONT><FONT color="#007700">(</FONT><FONT color="#DD0000">
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'green'</FONT><FONT color="#007700">);
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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FilledRectangle</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
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10</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">10</FONT><FONT
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color="#007700">,</FONT><FONT color="#0000BB">50</FONT><FONT color="#007700">
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,</FONT><FONT color="#0000BB">50</FONT><FONT color="#007700">);
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<BR>
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<BR></FONT><FONT color="#FF8000">// .. add a filled rounded rectangle
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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SetColor</FONT><FONT color="#007700">(</FONT><FONT color="#DD0000">
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'green'</FONT><FONT color="#007700">);
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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FilledRoundedRectangle</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
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300</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">30</FONT><FONT
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color="#007700">,</FONT><FONT color="#0000BB">350</FONT><FONT color="#007700">
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,</FONT><FONT color="#0000BB">80</FONT><FONT color="#007700">,</FONT><FONT
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color="#0000BB">10</FONT><FONT color="#007700">);
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<BR></FONT><FONT color="#FF8000">// .. with a darker border
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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SetColor</FONT><FONT color="#007700">(</FONT><FONT color="#DD0000">
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'darkgreen'</FONT><FONT color="#007700">);
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">img</FONT><FONT color="#007700">-></FONT><FONT color="#0000BB">
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RoundedRectangle</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
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300</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">30</FONT><FONT
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color="#007700">,</FONT><FONT color="#0000BB">350</FONT><FONT color="#007700">
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,</FONT><FONT color="#0000BB">80</FONT><FONT color="#007700">,</FONT><FONT
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color="#0000BB">10</FONT><FONT color="#007700">);
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<BR>
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<BR></FONT><FONT color="#FF8000">// Stroke the graph
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<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-></FONT><FONT
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color="#0000BB">Stroke</FONT><FONT color="#007700">();
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<BR>
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<BR></FONT><FONT color="#0000BB">?>
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<BR></FONT>
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<BR></FONT></CODE></DIV></P>
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<P> Pleas note the way to access these routines through the img property
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of the Graph class. Please also keep in mind that the coordinates are
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absolute.</P>
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<P><DIV class="example">
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<BR> <A href="exframes/frame_canvasex02.html" target="blank"><IMG border="0"
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HEIGHT="200" src="img/img/img/img/img/img/canvasex02.png" WIDTH="400"></A>
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<BR><B>Figure 189:</B> Example of graphic primitives <A href="exframes/frame_canvasex02.html"
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target="blank">[src]</A>
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<P></P>
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</DIV></P>
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<P></P>
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<P></P>
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<HR> <SMALL>
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<P><STRONG> A note on GD</STRONG> For those of you using GD 1.xx you
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might notice that the large "filled circle" isn't completely filled.
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This is because in GD 1.xx there are no low level primitives to fill an
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ellipse or circle so JpGraph tries to make the best out of a bad
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situation and manually fake a filled circle. For interest of speed
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JpGraph does not contain a complete (for example) Bresenham-circle fill
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but cheats by using some existing GD routines. This is not a perfect
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solution and for large filled circles like this you get some
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moire-patterns in the circle. If you upgrade to GD 2.x JpGraph will be
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able to make full use of those new existing methods and the fill will
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be perfect.</P>
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</SMALL>
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<HR>
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<P> We refer you to the class reference to find out what other graphic
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primitives are available for use.</P>
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