PIDDLE
Plug-In Drawing, Does Little Else
Abstract
PIDDLE is a Python module
for creating two-dimensional graphics in a manner that is both cross-platform
and cross-media; that is, it can support screen graphics (e.g. QuickDraw,
Windows, Tk) as well as file output (PostScript, PDF, GIF, etc.). It makes use
of the native 2D drawing calls of each backend, for maximum efficiency and
quality. It works by defining a base class (piddle.Canvas) with methods for
all supported drawing primitives. A particular drawing context is provided in
the form of a derived class. PIDDLE applications will be able to automatically
select an appropriate backend for the user's environment.
NEWS
2002-02-08: After a long hiatus, I've uploaded version
1.0.14. This is the first version to use distutils. Installation
should now be as easy as "python setup.py install" I've also thrown in
more exprimental backends--better to get them out there than just have
them languish. The new backends include SVG, GTK, Xfig, and improved
TK support. Thanks to all who contributed code! Note, I've dropped
the "b" marking the beta nature of the distribution. Got tired of
keeping track of whether it's a beta package or not. You should view
the documentation to see which backends are solid and which are
exprimental (see below).
Because of the not-so-positive connotations of the name "piddle", I have put
together a a development version with the same functionality and interface
under the the name "SPING" (Simple Platform Independent Graphics). I'm
looking for feedback on the name choice and if you have a better name, please
let us know on the piddle mailing list pythonpiddle@yahoogroups.com . In
addition to the name change, Sping is designed to be used as a python package
and is being developed using the Python Imaging Library version 1.1. To make
it easier to use PIL 1.1 on Windows, I've made a binary version of PIL 1.1
available as well (compiled under tk/tcl version 8.0.5). You can download the
latest versions of Sping and PIL-1.1-win32-bin . If you have problems reaching these links go to the alternative download page .
Important note: Sping
1.1.x, with it's odd numbered point release, is the development
branch of piddle, also known as the unstable branch. Stick with the
piddle-1.x releases if you require more guarantees of a stable and fixed api.
On the other hand, if you need new features, Sping-1.1.x is where they'll be
added.
Status
PIDDLE is reaching the end of beta testing and with the 1.0
stable release of select backends coming soon (4th quarter 2000 is the current
best guess). The PDF, PIL, wxWindows, PS, TK, and Quick Draw backends are solid.
The other backends will be included in the 1.0 distribution with opportunities
for further development in the development version (versions 1.1.x). If you do
find a bug still lurking, please send email to the PIDDLE mailing list
at pythonpiddle@yahoogroups.com
.
Piddle and Python 2.0
Piddle itself works perfectly with Python 2.0 and above. If you are upgrading, make
sure to upgrade/recompile any extension modules that you wish to use (e.g.
PIL) so that they work with Python 2.0 as well.
As of Febuary 8, 2002, the current release is 1.0.14 , however,
see the download page for the latest information.
As of 12 December 2000, the current release is 1.0b13 , however,
see the download page for the latest information.
Please note that PIDDLE requires Python 1.5.2, because it uses the
"extend" list method, which is not available in older versions of Python. In addition, it now includes distutils support which can be added to Python 1.5.2, but which comes by default with versions 1.6, 2.0 and above.
The standard distribution includes the following back-end renderers:
Notes:
[1] piddleTK relies upon piddlePIL for the drawing of rotated
strings.
The following backends are in various stages of development, and not yet
fully compliant. They are now included in the official distribution to encourage experimentation and improvements
Notes:
[5] winpiddle's string drawing is having some trouble with size and
color attributes; also, the text background is not transparent as it should
be. Unclear whether rotated strings are supported yet.
[6] piddleGTK doesn't yet draw rotated strings, but it is
planned.
[7] piddleFIG string widths are wrong at the moment
[8] piddleFIG images must be stored separately from the .fig file itself
since the .fig format only allows images to be included by referring to
them by filename
Usage Overview
PIDDLE is designed for vector graphics -- i.e., drawing of primitives such as
lines and ellipses, rather than manipulation of individual pixels. Generally,
one creates a PIDDLE drawing in four steps:
- instantiate a class derived from piddle.Canvas
- call drawing methods on that object, such as drawLine or drawString
- flush the canvas's buffer (i.e., flush the graphics pipeline, update the
screen, or whatever)
- Save the canvas's current view to a file if one is desired.
Note that while PIDDLE is easiest to use in a noninteractive mode -- i.e.,
simply generating charts, pictures, or other static displays -- some backends
support callback methods invoked when the mouse moves over or clicks on the
drawing. This allows for some graphical interaction with the user. The canvas
save() operation is most relevant to file-based backends (e.g. piddlePDF)
while the flush() command is most relevant to backends that produce on-screen
graphics.
Developer's Overview
Creating a new PIDDLE backend is relatively easy. You must create a class
derived from piddle.Canvas, and instantiate at least the following methods:
- drawLine
- drawPolygon
- drawImage
- drawString
All other drawing methods will have default implementations in terms of the
functions above. However, you may wish to also override other drawing methods
for the sake of efficiency or quality.
Documentation
In addition, information specific to individual backends are placed in the
docs/notes* directories
Examples
| This example illustrates a hodgepodge of
PIDDLE drawing commands, including lines, curves, polygons, arcs,
roundrects, and rotated text. The graphic shown here was rendered with
the QuickDraw backend; other backends may
vary, especially in the appearance of the text. |
 |
| This spectrum chart is actually a useful
program; I needed to generate a spectrum for a scientific application,
and this is the PIDDLE program I used to do it. In this program, I
defined a factory function 'makeCanvas' at the top of the program to
create the canvas. To use a backend other than QuickDraw, you'll only
need to modify this function. |
 |
| A string test module puts PIDDLE's
font and string handling through the paces. It illustrates the
standard fonts which every backend should be able to understand (and
hopefully display). |
 |
| A string rotation test module exercises
the drawing of rotated strings at a variety of angles (in rainbow
colors, no less). Example output is shown for both QuickDraw and PIL.
Note that the two have somewhat different ideas about how big a
12-point (default) font should be; this sort of discrepancy is
inevitable, at least for now. |
 |
More examples are included with the distribution in the examples directory and
in piddletest.py, a file which allows you to select any test, and pair
it with any standard backend renderer.
Credits & Feedback
PIDDLE was initially designed and implemented by
a small international team of Python coders. There is a mailing list for
discussion of PIDDLE at
http://groups.yahoo.com/group/pythonpiddle . To get your feedback to the
list send email to
pythonpiddle@yahoogroups.com .
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