Clipping symbols

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Clipping symbols

Magnus Homann
In the rendering branch I'm trying to fix clipping of hard symbols
(#705). Much of the confusion comes from the fact the pointSize does not
determine a rectangular boundigbox, but instead specifies an area.

So, for a hard marker with pointSize=10, the area should be the same
between circel, rectangle, diamond and triangle, with the circle as the
determining symbol.

The interesting thing happens when you specifiy a diamond fitting into a
10x10 box, and with the same areas as a circle with radius=5. Not so
easy withou clipping!

And then there is the line width... :-)

Can we all agree that instead a symbol with pointSize=10 should render a
circle with radius=5, a rectangel with side=10, a diamond with
*diagonal*=10 and a triangle with base and height=10. They will then all
have different areas.

The numbers above are including line width, so there will be no exact
area scale.

(Hmm, I got a deja vu writing this. Tim, did we discuss this a couple of
years back? Creepy...)

Magnus
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Re: Clipping symbols

Tim Sutton
Hi

Sounds good to me. I think the important things are that:

a) the fixed symbols all appear simlar sized relative to each other
b) they apear similar in size relative to svg symbols of the same size

It will be great if you can fix those clipping issues!

Regards

Tim

2008/1/8, Magnus Homann <[hidden email]>:

> In the rendering branch I'm trying to fix clipping of hard symbols
> (#705). Much of the confusion comes from the fact the pointSize does not
> determine a rectangular boundigbox, but instead specifies an area.
>
> So, for a hard marker with pointSize=10, the area should be the same
> between circel, rectangle, diamond and triangle, with the circle as the
> determining symbol.
>
> The interesting thing happens when you specifiy a diamond fitting into a
> 10x10 box, and with the same areas as a circle with radius=5. Not so
> easy withou clipping!
>
> And then there is the line width... :-)
>
> Can we all agree that instead a symbol with pointSize=10 should render a
> circle with radius=5, a rectangel with side=10, a diamond with
> *diagonal*=10 and a triangle with base and height=10. They will then all
> have different areas.
>
> The numbers above are including line width, so there will be no exact
> area scale.
>
> (Hmm, I got a deja vu writing this. Tim, did we discuss this a couple of
> years back? Creepy...)
>
> Magnus
> _______________________________________________
> Qgis-developer mailing list
> [hidden email]
> http://lists.qgis.org/cgi-bin/mailman/listinfo/qgis-developer
>


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Tim Sutton
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Re: Clipping symbols

Steven Bell
In reply to this post by Magnus Homann
Can we all agree that instead a symbol with pointSize=10 should render a
circle with radius=5, a rectangel with side=10, a diamond with
*diagonal*=10 and a triangle with base and height=10. They will then all
have different areas.
I would vote for that.  When you specify a size in pixels, millimeters, or map units, you expect the symbol to be that size, not some area-equivalent size.  Note that an equilateral triangle (if that's what the symbol is meant to be) will have a base of 10 and a height less than 10.  On a similar note, some of the svg point symbols should be modified to fill the entire svg canvas.
Steven
 

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