[Carto] Introduction and initial thoughts.
lblake at ksninc.com
Tue Apr 6 14:25:10 EDT 2010
I just subscribed to the carto mailing list. I wanted to briefly
introduce myself and then respond to some of Tyler's comments.
My name is Landon (AKA "The Sunburned Surveyor) and I am a volunteer
programmer on OpenJUMP. I also work a little on the OSGeo Journal, the
OSGeo Google SoC Program, and with the California Chapter.
I'm certainly interested in improving the shared cartographic output of
open source geospatial applications and in helping OpenJUMP participate
in any system developed by OSGeo volunteers.
Tyler wrote: "...the "Carto" project is an effort to address this in a
standard way, so that all open source applications may output
configuration files according to a specification and have a common
'engine' application produce an output file. By using a standards-based
approach, developers can work together on improving printing output
overall instead of doing it in dozens of different ways."
This is an important statement that I believe captures some critical
ideas. Let me break it into a couple of chunks. The first chunk deals
with the "specification". The second chunk deals with the "engine".
It sounds like we need to determine an input specification for our
rendering engine. I think this input specification would need to define
three things about the map to be rendered by the engine:
(1) The features being rendered.
(2) The style in which to render features.
(3) The layout of the map sheet.
I think our engine should suck in a file format that meets the spec and
produce output in a common graphics format like SVG, EPS, PDF, and image
We may already be a lot closer to a simple system that operates like
this than you might think. Let me tell you what I have been working on
for OpenJUMP and how it could be tweaked to be the basis for a baby
OSGeo Carto project.
I'm working on a plug-in for OpenJUMP that creates an SVG page and SVG
geoemtry from a set of simple features. I'm calculating all of the
necessary transformations and conversions in my own code. This gives me
more control than using a library like Batik. The conversion parameters
(page size, line thickness, line pattern, etc.) are stored in a text
file. The SVG that my plug-in creates is currently tailored for
It wouldn't take a lot of work to modify this plug-in into a stand-alone
application that did the following:
(1) Read an input file with the conversion parameters.
(2) Read an input file of WKT or a Shapefile defining simple features.
(3) Use this information to create an SVG file.
Of course this simple application leaves great room for improvement. I'm
working in Java, and that isn't a programming language everyone loves.
If we only suck in WKT (and not something like a shapefile), then we
loose the ability to calculate labels based on simple feature attribute
values. We eventually want to support more output formats. I started
with SVG, but it wouldn't be hard to add support for PDF and DXF, as
there are open source Java libraries for working with both file formats.
I certainly want to hear what others think, but I'm willing to abandon
my OpenJUMP plug-in to start work on a basic OSGeo Carto application
like the one I described. I think I could have an alpha distribution
ready to go in a few weeks.
Please let me know what you guys think. I'm excited about this project
and eager to have some of my existing code benefit others.
Office Phone Number: (209) 946-0268
Cell Phone Number: (209) 992-0658
From: carto-bounces at lists.osgeo.org
[mailto:carto-bounces at lists.osgeo.org] On Behalf Of
carto-request at lists.osgeo.org
Sent: Tuesday, April 06, 2010 10:34 AM
To: Landon Blake
Subject: Welcome to the "Carto" mailing list
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