Appendix¶

API and Implementation Notes¶

External Interface¶

Most users of the module will use one of the following two functions. They provide a high level interface. They are also directly accessible as aafigure.process respectively aafigure.render.

aafigure.aafigure.process(input, visitor_class, options=None)¶

Parse input and render using the given visitor class.

Parameters:	input – String or file like object with the image as text. visitor_class – A class object, it will be used to render the resulting image. options – A dictionary containing the settings. When `None` is given, defaults are used.
Returns:	instantiated `visitor_class` and the image has already been processed with the visitor.
Exception:	This function can raise an `UnsupportedFormatError` exception if the specified format is not supported.

aafigure.aafigure.render(input, output=None, options=None)¶

Render an ASCII art figure to a file or file-like.

Parameters:	input – If `input` is a basestring subclass (str or unicode), the text contained in `input` is rendered. If input is a file-like object, the text to render is taken using ``input.read(). output – If no `output` is specified, the resulting rendered image is returned as a string. If output is a basestring subclass, a file with the name of `output` contents is created and the rendered image is saved there. If `output` is a file-like object, `output.write()` is used to save the rendered image. options – A dictionary containing the settings. When `None` is given, defaults are used.
Returns:	This function returns a tuple `(visitor, output)`, where `visitor` is visitor instance that rendered the image and `output` is the image as requested by the `output` parameter (a `str` if it was `None`, or a file-like object otherwise, which you should `close()` if needed).
Exception:	This function can raise an `UnsupportedFormatError` exception if the specified format is not supported.

The command line functionality is implemented in the main function.

aafigure.aafigure.main()¶: implement an useful main for use as command line program

Internal Interface¶

The core functionality is implemented in the following class.

class aafigure.aafigure.AsciiArtImage(text, options=None)¶

This class holds a ASCII art figure and has methods to parse it. The resulting list of shapes is also stored here.

The image is parsed in 2 steps:

horizontal string detection.
generic shape detection.

Each character that is used in a shape or string is tagged. So that further searches don’t include it again (e.g. text in a string touching a fill), respectively can use it correctly (e.g. join characters when two or more lines hit).

__init__(text, options=None)¶: Take a ASCII art figure and store it, prepare for recognize

recognize()¶: Try to convert ASCII art to vector graphics. The result is stored in self.shapes.

Images are built using the following shapes. Visitor classes must be able to process these types.

class aafigure.shapes.Arc(start, start_angle, end, end_angle, start_curve=True, end_curve=True)¶: A smooth arc between two points

class aafigure.shapes.Circle(center, radius)¶: Circle with center coordinates and radius.

class aafigure.shapes.Group(shapes=None)¶: A group of shapes

class aafigure.shapes.Label(position, text)¶: A text label at a position

class aafigure.shapes.Line(start, end, thick=False)¶: Line with starting and ending point. Both ends can have arrows

class aafigure.shapes.Point(x, y)¶: A single point. This class primary use is to represent coordinates for the other shapes.

class aafigure.shapes.Rectangle(p1, p2)¶: Rectangle with two edge coordinates.

aafigure.shapes.group(list_of_shapes)¶: return a group if the number of shapes is greater than one

aafigure.shapes.point(obj)¶: return a Point instance. - if object is already a Point instance it’s returned as is - complex numbers are converted to Points - a tuple with two elements (x,y)

Options¶

The options dictionary is used in a number of places. Valid keys (and their defaults) are:

Defining the output:

file_like <str>:

Use the given file like object to write the output. The object needs to support a .write(data) method.

format <str>:

Choose backend/output format: ‘svg’, ‘pdf’, ‘png’ and all bitmap formats that PIL supports can be used but only few make sense. Line drawings have a good compression and better quality when saved as PNG rather than a JPEG. The best quality will be achieved with SVG, tough not all browsers support this vector image format at this time (default: 'svg').

Options influencing how an image is parsed:

textual <bool>:

Disables horizontal fill detection. Fills are only detected when they are vertically at least 2 characters high (default: False).

textual_strict <bool>:

Disables fill detection completely. (default: False).

proportional <bool>:

Use a proportional font. Proportional fonts are general better looking than monospace fonts but they can mess the figure if you need them to look as similar as possible to the ASCII art (default: False).

Visual properties:

background <str>:

Background color in the form #rgb or #rrggbb, not for SVG output (default: #000000).

foreground <str>:

Foreground color in the form #rgb or #rrggbb (default: #ffffff).

fill <str>:

Fill color in the form #rgb or #rrggbb (default: same as foreground color).

line_width <float>:

Change line with, SVG only currently (default: 2.0).

scale <float>:

Enlarge or shrink image (default: 1.0).

aspect <float>:

Change aspect ratio. Effectively it is the width of the image that is multiplied by this factor. The default setting 1 is useful when shapes must have the same look when drawn horizontally or vertically. However, 0.5 looks more like the original ASCII and even smaller factors may be useful for timing diagrams and such. But there is a risk that text is cropped or is drawn over an object besides it.

The stretching is done before drawing arrows or circles, so that they are still good looking (default: 1.0).

Miscellaneous options:

debug <bool>:

For now, it only prints the original ASCII art figure text (default: False).

Visitors¶

A visitor that can be used to render the image must provide the following function (it is called by process())

class your.Visitor¶

visit_image(aa_image)¶

An AsciiArtImage instance is passed as parameter. The visiting function needs to implement a loop processing the shapes attribute.

This function must take care of actually outputting the resulting image or it must provide the data in a form useful for the caller (process() returns the visitor so that the result can be read for example).

Example stub class:

class Visitor:
    def visit_image(self, aa_image):
        self.visit_shapes(aa_image.shapes)

    def visit_shapes(self, shapes):
        for shape in shapes:
            shape_name = shape.__class__.__name__.lower()
            visitor_name = 'visit_%s' % shape_name
            if hasattr(self, visitor_name):
                getattr(self, visitor_name)(shape)
            else:
                sys.stderr.write("WARNING: don't know how to handle shape %r\n"
                    % shape)

    def visit_group(self, group):
        self.visit_shapes(group.shapes)

    # for actual output implement visitors for all the classes in
    # aafigure.shapes:

    def visit_line(self, lineobj):
        ...
    def visit_circle(self, circleobj):
        ...
    etc...

Source tree¶

The sources can be checked out using bazaar:

bzr lp:aafigure

Files in the aafigure package:

aafigure.py: ASCII art parser. This is the main module.
shapes.py: Defines a class hierachy for geometric shapes such as lines, circles etc.
error.py: Define common exception classes.
aa.py: ASCII art output backend. Intended for tests, not really useful for the end user.
pdf.py: PDF output backend. Depends on reportlab.
pil.py: Bitmap output backend. Using PIL, it can write PNG, JPEG and more formats.
svg.py: SVG output backend.

Files in the docutils directory:

aafigure_directive.py: Implements the aafigure Docutils directive that takes these ASCII art figures and generates a drawing.

The aafigure module contains code to parse ASCII art figures and create a list of of shapes. The different output modules can walk through a list of shapes and write image files.

TODO¶

Symbol detection: scan for predefined shapes in the ASCII image and output them as symbol from a library
Symbol libraries for UML, flowchart, electronic schematics, ...
The way the image is embedded is a hack (inserting a tag trough a raw node...)
Search for ways to bring in color. Ideas:
- have an :option: to set color tags. Shapes that touch such a tag inherit it’s color. The tag would be visible in the ASCII source tough:
  .. aafig:: :colortag: 1:red, 2:blue 1---> --->2
- :color: x,y,color but counting coordinates is no so fun
drawback: both are complex to implement, searching for shapes that belong together. It’s also not always wanted that e.g. when a line touches a box, both have the same color
aafigure probably needs arguments like font-family, ...
Punctuation not included in strings (now a bit improved but if it has a graphical meaning , then that is chooses, even if it makes no sense), underlines in strings are tricky to detect...
Dotted lines? ... e.g. for ---...--- insert a dashed line instead of 3 textual dots. Vertical dashed lines should also work with :.
Group shapes that belong to an object, so that it’s easier to import and change the graphics in a vector drawing program. [partly done]
Path optimizer, it happens that many small lines are output where a long line could be used.

3rd party integration of aafigure¶

There are also other projects that integrate aafigure. The following items are maintained by other developers.

MediaWiki Plug-in¶

MediaWiki is a popular implementation of a WikiWikiWeb which is also used for WikiPedia. A plug-in can be found here: http://www.mediawiki.org/wiki/Extension:Aafigure

AsciiDoc Plug-in¶

AsciiDoc is a plain text documentation format that can be converted into several formats such as HTML or PDF. A plug-in to use aafigure drawings in such documents can be found here: http://code.google.com/p/asciidoc-aafigure-filter/

Authors and Contact¶

Chris Liechti: original author
Leandro Lucarella: provided many patches

The project page is at https://launchpad.net/aafigure It should be used to report bugs and feature requests.

License¶

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
Neither the name of the aafigure-team nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE AAFIGURE-TEAM ‘’AS IS’’ AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AAFIGURE-TEAM BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.