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<div class="moz-cite-prefix">Hi Chris,<br>
<br>
Thanks for your advice :)<br>
<br>
I used XFillArc(Xlib stuff) instead
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<a
href="https://github.com/xiangzhai/grt/blob/master/GRTExamples/ClassificationModulesExamples/X11DTWExample/x11.cpp#L227">https://github.com/xiangzhai/grt/blob/master/GRTExamples/ClassificationModulesExamples/X11DTWExample/x11.cpp#L227</a><br>
<br>
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<blockquote
cite="mid:20131006090502.GA14951@nuc-i3427.alporthouse.com"
type="cite">
<pre wrap="">On Sun, Oct 06, 2013 at 03:50:59PM +0800, Leslie Zhai wrote:
</pre>
<blockquote type="cite">
<pre wrap=""> Hi cairo developers,
I wanna draw some points indicating mouse`s X and Y, and used random
number from 0 to 255 for RGB color of the points, such as:
for loop
{
double r = Map(i, 0, 100, 0, 255); // Re-maps a number from one
range to another
[1]<a class="moz-txt-link-freetext" href="http://www.openframeworks.cc/documentation/math/ofMath.html#show_ofMap">http://www.openframeworks.cc/documentation/math/ofMath.html#show_ofMap</a>
double g =
0;
double b = 255 -
r;
cairo_set_source_rgb(c, r / 255.0, g / 255.0, b /
255.0);
cairo_move_to(c, x,
y);
cairo_close_path(c);
}
cairo_stroke(c);
It is unable to put cairo_stroke into the for loop, it might be a heavy
operation when draw the path too often.
But cairo_set_source_rgb failed to take effect in the loop if cairo_stroke
was outside.
The source code is available via
[2]<a class="moz-txt-link-freetext" href="https://github.com/xiangzhai/grt/tree/master/GRTExamples/ClassificationModulesExamples/CairoX11DTWExample">https://github.com/xiangzhai/grt/tree/master/GRTExamples/ClassificationModulesExamples/CairoX11DTWExample</a>
So how to take cairo_set_source_rgb effect for drawing different color
points?
Please someone give me some advice, Thanks a lot :)
</pre>
</blockquote>
<pre wrap="">
You can't store color per-path as stroke/fill operate upon the path union.
For the same reason calling stroke 100 times for a simple path is likely to
be a lot cheaper than calling it once with a 100-fold more complex path.
And you probably don't want to use stroke here unless you have a wide
pen and wish to use the pen to draw dots.
-Chris
</pre>
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