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<H2><A NAME="11_2">11.2 Creating a simple canvas</A></H2>
<P> In order to create a canvas graph you need to include the file
 &quot;jpgraph_canvas.php&quot; in addition to the standard &quot;jpgraph.php&quot; file.
 You might also want to include the &quot;jpgraph_canvtools.php&quot; to get
 access to some supporting classes that may (or not) come in handy.</P>
<P> Creating a canvas gives you the opportunity draw arbitrary shapes on
 a &quot;white&quot; piece of paper. Let's first show a simple example were we
 just draw a text box. We first show you the code which we will walk
 through<DIV class="phpscript">(File: canvasex01.php)
<BR><CODE><FONT color="#000000"> <FONT color="#0000BB">&lt;?php
<BR></FONT><FONT color="#FF8000">
//&nbsp;$Id:&nbsp;canvasex01.php,v&nbsp;1.3&nbsp;2002/10/23&nbsp;08:17:23&nbsp;aditus&nbsp;Exp&nbsp;$
<BR></FONT><FONT color="#007700">include&nbsp;</FONT><FONT color="#DD0000">
&quot;../jpgraph.php&quot;</FONT><FONT color="#007700">;
<BR>include&nbsp;</FONT><FONT color="#DD0000">&quot;../jpgraph_canvas.php&quot;</FONT><FONT
color="#007700">;
<BR>
<BR></FONT><FONT color="#FF8000">//&nbsp;Setup&nbsp;a&nbsp;basic&nbsp;canvas&nbsp;we&nbsp;can&nbsp;work&nbsp;
<BR></FONT><FONT color="#0000BB">$g&nbsp;</FONT><FONT color="#007700">=&nbsp;new&nbsp;</FONT><FONT
color="#0000BB">CanvasGraph</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
400</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">300</FONT><FONT
color="#007700">,</FONT><FONT color="#DD0000">'auto'</FONT><FONT color="#007700">
);
<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-&gt;</FONT><FONT
color="#0000BB">SetMargin</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
5</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">11</FONT><FONT
color="#007700">,</FONT><FONT color="#0000BB">6</FONT><FONT color="#007700">
,</FONT><FONT color="#0000BB">11</FONT><FONT color="#007700">);
<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-&gt;</FONT><FONT
color="#0000BB">SetShadow</FONT><FONT color="#007700">();
<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-&gt;</FONT><FONT
color="#0000BB">SetMarginColor</FONT><FONT color="#007700">(</FONT><FONT color="#DD0000">
&quot;teal&quot;</FONT><FONT color="#007700">);
<BR>
<BR></FONT><FONT color="#FF8000">
//&nbsp;We&nbsp;need&nbsp;to&nbsp;stroke&nbsp;the&nbsp;plotarea&nbsp;and&nbsp;margin&nbsp;before&nbsp;we&nbsp;add&nbsp;the
<BR>//&nbsp;text&nbsp;since&nbsp;we&nbsp;otherwise&nbsp;would&nbsp;overwrite&nbsp;the&nbsp;text.
<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-&gt;</FONT><FONT
color="#0000BB">InitFrame</FONT><FONT color="#007700">();
<BR>
<BR></FONT><FONT color="#FF8000">//&nbsp;Draw&nbsp;a&nbsp;text&nbsp;box&nbsp;in&nbsp;the&nbsp;middle
<BR></FONT><FONT color="#0000BB">$txt</FONT><FONT color="#007700">=</FONT><FONT
color="#DD0000">&quot;This\nis\na&nbsp;TEXT!!!&quot;</FONT><FONT color="#007700">;
<BR></FONT><FONT color="#0000BB">$t&nbsp;</FONT><FONT color="#007700">=&nbsp;new&nbsp;</FONT><FONT
color="#0000BB">Text</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
$txt</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">200</FONT><FONT
color="#007700">,</FONT><FONT color="#0000BB">10</FONT><FONT color="#007700">
);
<BR></FONT><FONT color="#0000BB">$t</FONT><FONT color="#007700">-&gt;</FONT><FONT
color="#0000BB">SetFont</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
FF_ARIAL</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">
FS_BOLD</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">40</FONT><FONT
color="#007700">);
<BR>
<BR></FONT><FONT color="#FF8000">
//&nbsp;How&nbsp;should&nbsp;the&nbsp;text&nbsp;box&nbsp;interpret&nbsp;the&nbsp;coordinates?
<BR></FONT><FONT color="#0000BB">$t</FONT><FONT color="#007700">-&gt;</FONT><FONT
color="#0000BB">Align</FONT><FONT color="#007700">(</FONT><FONT color="#DD0000">
'center'</FONT><FONT color="#007700">,</FONT><FONT color="#DD0000">'top'</FONT><FONT
color="#007700">);
<BR>
<BR></FONT><FONT color="#FF8000">//&nbsp;How&nbsp;should&nbsp;the&nbsp;paragraph&nbsp;be&nbsp;aligned?
<BR></FONT><FONT color="#0000BB">$t</FONT><FONT color="#007700">-&gt;</FONT><FONT
color="#0000BB">ParagraphAlign</FONT><FONT color="#007700">(</FONT><FONT color="#DD0000">
'center'</FONT><FONT color="#007700">);
<BR>
<BR></FONT><FONT color="#FF8000">
//&nbsp;Add&nbsp;a&nbsp;box&nbsp;around&nbsp;the&nbsp;text,&nbsp;white&nbsp;fill,&nbsp;black&nbsp;border&nbsp;and&nbsp;gray&nbsp;shadow
<BR></FONT><FONT color="#0000BB">$t</FONT><FONT color="#007700">-&gt;</FONT><FONT
color="#0000BB">SetBox</FONT><FONT color="#007700">(</FONT><FONT color="#DD0000">
&quot;white&quot;</FONT><FONT color="#007700">,</FONT><FONT color="#DD0000">
&quot;black&quot;</FONT><FONT color="#007700">,</FONT><FONT color="#DD0000">&quot;gray&quot;</FONT><FONT
color="#007700">);
<BR>
<BR></FONT><FONT color="#FF8000">//&nbsp;Stroke&nbsp;the&nbsp;text
<BR></FONT><FONT color="#0000BB">$t</FONT><FONT color="#007700">-&gt;</FONT><FONT
color="#0000BB">Stroke</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
$g</FONT><FONT color="#007700">-&gt;</FONT><FONT color="#0000BB">img</FONT><FONT
color="#007700">);
<BR>
<BR></FONT><FONT color="#FF8000">//&nbsp;Stroke&nbsp;the&nbsp;graph
<BR></FONT><FONT color="#0000BB">$g</FONT><FONT color="#007700">-&gt;</FONT><FONT
color="#0000BB">Stroke</FONT><FONT color="#007700">();
<BR>
<BR></FONT><FONT color="#0000BB">?&gt;
<BR></FONT>
<BR></FONT></CODE></DIV></P>
<P> The example above starts by creating a (400x200) sized image. We set
 the margins to get a nice frame around the image. For canvases the
 margins has no effect in the way you enter coordinates. Top left is
 (0,0) and bottom right (including any potential margin and shadow) is
 the maximum. In this case the coordinates are X:0-399, and Y:0-199</P>
<P> We then call the <A href="../ref/CanvasGraph.html#_CANVASGRAPH_INITFRAME">
 InitFrame()</A> method which actually strokes the margin and plotarea
 to the graph. Since everything is stroked in the order you issue the
 commands you must make sure that the graphical objects you want on top
 is stroked last. This is different from the way you normally work with
 JpGraph since it queues up all you addition and then makes sure they
 are stroked in the correct order.</P>
<P> We then create a <A href="../ref/Text.html#_C_TEXT">Text</A> object,
 setup it's properties, including the absolute screen position where we
 want the text, and then stroke it. Her it might be a need for a closer
 explanation of the, perhaps misnamed, method <A href="../ref/Text.html#_TEXT_ALIGN">
Text::Align()</A> This method states<STRONG> how the text coordinates
 should be interpreted</STRONG> , i.e when we specify (200,10) as the
 coordinates for the text paragraph should that be interpreted as the
 top left corner, bottom-left corner or something else (of the bounding
 box)? In the code above we have chosen to interpret the X-coordinate as
 being the center of the bounding box and the Y-coordinate as the top.
 Hence the text will be aligned so that the (200,100) point in the graph
 is aligned with the middle of the top line of the paragraphs bounding
 box.</P>
<P> We also specify that the lines within the paragraph should be
 centered with a call to <A href="../ref/Text.html#_TEXT_PARAGRAPHALIGN">
 Text::ParagraphAlign()</A> Since we also choose to have a box around
 the text we have to make use of the method <A href="../ref/Text.html#_TEXT_SETBOX">
 Text::SetBox()</A> which is used to specify the fill color, the border
 color and the shadow color (if you leave out shadow color or set it to
 '', no shadow will be used).</P>
<P> Now we are ready to stroke the text onto the canvas. In order to do
 so we must specify the basic Image drawing class we want to use.
 Without discussing this further we just state that a suitable image
 class can always be found as the<STRONG> img</STRONG> property of the
 Graph class.</P>
<P> Finally we are ready to stroke the entire graph, which in effect
 sends the canvas back to the browser. Below you can see the effect of
 all this code</P>
<P><DIV class="example">
<BR> <A href="exframes/frame_canvasex01.html" target="blank"><IMG border="0"
HEIGHT="300"  src="img/canvasex01.png" WIDTH="400"></A>
<BR><B>Figure 184:</B> A simple canvas drawing with a text box in the
 middle <A href="exframes/frame_canvasex01.html" target="blank">[src]</A>
&nbsp;
<P></P>
</DIV></P>
<P></P>
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