[Shapelib] Shapefile questions - newbie

Curt, WE7U archer at eskimo.com
Tue Jun 7 13:35:30 EDT 2005

On Tue, 7 Jun 2005, Cook, Steve wrote:

> The shapefile format does not seem to support drawing attributes such as
> line width, color, etc...  The FAQ indicates that its up to the imaging
> application to decide how to display items.  Is the dbx file used to
> indicate/hint about what the shape is (e.g. a road, river, etc...) and
> if so how?  Or is there some other way of indicating how to draw shape
> objects?  In my case I'm wanting to draw weather fronts.

Attributes are stored in the DBF file.  It's up to the application
how to use this information.  One open-source application I work on
had to add a separate file in order to key the application as to
which fields were present in the DBF file and how to display them.
There is no standard and each source of Shapefiles does it

> Does the shape format support any kind of text display?  Do I need to
> create my own font vectorizer?

Text goes in DBF file in some field or other.  You could add other
fields to describe the font size, color, orientation, etc.

> How do I define objects that are pixel size related (but still
> geo-located).  That is, I want a constant size on the screen no matter
> how much I zoom in or out.

How I'd go about it:  Use a Point Shapefile.  In the DBF file that
goes with it you'd have attributes that would specify the pixel size
for it.  The application would need to be smart enough to use this

> steve.cook at ngc.com
> Lakewood, WA

Hello down there... I'm north of Seattle.

I could talk to you some more about it off-line if you wish.  I
contribute heavily to an open-source mapping program that uses
Shapelib and others.

Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
"Lotto:    A tax on people who are bad at math." -- unknown
"Windows:  Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me:  I picked the coordinate system!"

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