13.1 theme - Defining the default behaviour of PyChart
You can change PyChart's behavior by setting variables in the module
theme
. After setting values, you must call
theme.reinitialize()
to reflect the changes to other parts of
PyChart.
Notice that these variables are meaningful only before the first call to
area.T.draw() (see Section 6).
The below are the list of variables in the theme
module that you can
modify.
- scale_factor
-
This variable defines the scaling factor.
The default value is 1.0, meaning that
one point in PyChart actually means one PostScript point.
Setting this value to
3.0, for example, makes PyChart draw everything three times larger.
See Also:
See Section
4 for how the length and the coordinate system
are defined in PyChart.
- output_format
-
This variable sets the encoding of the data produced by PyChart.
The value of this variable must be one of the following strings.
ps
:
-
eps
:
-
Encapsulated PostScript. This is the default.
pdf
:
- Adobe Page Description Format, or PDF.
pdf-uncompressed
:
- PDF without compression.
This option should be used for a debugging purpose only.
png
:
- PNG graphics. You need to have ghostscript (
gs
) installed to use
this option, because PyChart internally calls ghostscript to convert
PostScript to PNG.
svg
:
- Scalable vector graphics.
x11
:
- Interactive display on in X window. This format works on UNIX-based
systems, but not on Windows. You need to have ghostscript installed to
use this option.
When this variable is not set (or is set to None
),
PyChart guesses the format from the file name
(theme.output_file
; see below).
Failing that, PyChart will generate
an encapsulated PostScript file.
- output_file
-
Sets the output file name. Without this option, PyChart sends code
to the standard output.
If you want to produce multiple charts from a single Python source file,
use
canvas.init(file)
(see Section 21).
- use_color
-
The default value of this variable is
False
.
If the value is True
,
PyChart colorizes some of the default objects.
If the value is False
, PyChart uses gray scale for the color of
these objects.
In particular:
- The standard color list (
colors.standards
) will include all
the colors listed in X's RGB file. So you can use something like
"color.slate_blue
"1.
See Section 15 for more about colors.
- The standard fill style list (
fill_style.standards
) will
be colorized. Thus, if you create a bar plot without explicitly
specifying its fill style, you will see colored bars on the canvas.
See Section 16 for more about fill styles.
- The standard line style list (
line_style.standards
) will be colorized.
See Section 14 for more about line styles.
- default_font_family
-
This variable sets the default font family used when
drawing texts. The default is Helvetica.
See Section 17.1.
- default_font_size
-
This variable sets the font size used when
drawing texts. The default is 9 points.
See Section 17.1.
- default_halign
-
Sets the default horizontal alignment of texts (Default value:
/h
).
See Section 17.1.
- default_valign
-
Sets the default vertical alignment of texts (Default value:
/v
).
See Section 17.1.
- default_angle
-
Default text-drawing angle (Default value: 0).
See Section 17.1.
- default_line_height
-
Defines the separation between two text lines.
See Section 17.1.
- default_line_width
-
Set the default line width, in points ( see Section 4). (Default value: 0.4)
See Section 14.
- debug_level
-
This variable controls the verbosity of messages from PyChart. The
default value is 1, meaning that PyChart only displays error
messages. The larger the value, the more verbose PyChart becomes.
- bounding_box
-
This variable, if set, manually sets the bounding box of the
chart(s) produced by PyChart. It is a four-tuple of numbers, i.e.,
(xmin, ymin, xmax, ymax).
PyChart usually calculates
the bounding box of a chart
automatically. Thus, you set this variable only
when you want to override the
calculation by PyChart, or PyChart screws the calculation. The latter
situation happens especially when you use really thick lines for
drawing. See also
delta_bounding_box
, described next.
- delta_bounding_box
-
This variable, if set, adjusts the size of the bounding box of
the chart(s).
It is a four-tuple of numbers (xmin, ymin, xmax, ymax). Each of the number is added to the bounding box computed by
PyChart.
If both bounding_box
and delta_bounding_box
are
set, then delta_bounding_box
is ignored.
After changing any of the variables described so far, you must
call the reinitialize
function to reflect the change to
the rest of PyChart:
-
This procedure must be called after setting variables in
the
theme
module. This procedure propagates the new values of
the theme variables to other modules that depend on their values.
Footnotes
- ...color.slate_blue"1
- In fact, you can use these color names
in gray-scale mode as well. They will appear in some gray color though.
Documentation released on July 2, 2005.