In addition it
contains the class
canvas.clip which allows clipping of the output.
This is the basic class of the canvas module. Instances of this class collect
visual elements like paths, other canvases, TeX or LaTeX elements. A canvas may
also be embedded in another one using its
insert method. This may be useful
when you want to apply a transformation on a whole set of operations.
- class canvas.canvas(attrs=, texrunner=None, ipython_bboxenlarge=1 * unit.t_pt)¶
Construct a new canvas, applying the given attrs, which can be instances of
style.fillstyle. The texrunner argument can be used to specify the texrunner instance used for the
text()method of the canvas. If not specified, it defaults to text.defaulttexrunner. ipython_bboxenlarge defines the bboxenlarge
document.pagefor IPython’s _repr_png_ and _repr_svg_.
Paths can be drawn on the canvas using one of the following methods:
- canvas.draw(path, attrs)¶
Draws path on the canvas applying the given attrs. Depending on the attrs the path will be filled, stroked, ornamented, or a combination thereof. For the common first two cases the following two convenience functions are provided.
- canvas.fill(path, attrs=)¶
Fills the given path on the canvas applying the given attrs.
- canvas.stroke(path, attrs=)¶
Strokes the given path on the canvas applying the given attrs.
Arbitrary allowed elements like other
canvas instances can be inserted
in the canvas using
- canvas.insert(item, attrs=)¶
Inserts an instance of
base.canvasiteminto the canvas. If attrs are present, item is inserted into a new
canvasinstance with attrs as arguments passed to its constructor. Then this
canvasinstance is inserted itself into the canvas.
Text output on the canvas is possible using
- canvas.text(x, y, text, attrs=)¶
Inserts text at position (x, y) into the canvas applying attrs. This is a shortcut for
insert(texrunner.text(x, y, text, attrs)).
To group drawing operations, layers can be used:
- canvas.layer(name, above=None, below=None)¶
This method creates or gets a layer with name name.
A layer is a canvas itself and can be used to combine drawing operations for ordering purposes, i.e., what is above and below each other. The layer name name is a dotted string, where dots are used to form a hierarchy of layer groups. When inserting a layer, it is put on top of its layer group except when another layer instance of this group is specified by means of the parameters above or below.
canvas class provides access to the total geometrical size of its
A canvas also allows to set its TeX runner:
Sets a new texrunner for the canvas.
The contents of the canvas can be written to a file using the following convenience methods, which wrap the canvas into a single page document.
- canvas.writeEPSfile(file, **kwargs)¶
Writes the canvas to file using the EPS format. file either has to provide a write method or it is used as a string containing the filename (the extension
.epsis appended automatically, if it is not present). This method constructs a single page document, passing kwargs to the
document.pageconstructor for all kwargs starting with
page_(without this prefix) and calls the
writeEPSfile()method of this
document.documentinstance passing the file and all kwargs starting with
write_(without this prefix).
- canvas.writetofile(filename, *args, **kwargs)¶
Determine the file type (EPS, PS, PDF, or SVG) from the file extension of filename and call the corresponding write method with the given arguments arg and kwargs.
- canvas.pipeGS(device, resolution=100, gscmd='gs', gsoptions=, textalphabits=4, graphicsalphabits=4, ciecolor=False, input='eps', **kwargs)¶
This method pipes the content of a canvas to the ghostscript interpreter to generate other output formats. The output is returned by means of a python BytesIO object. device specifies a ghostscript output device by a string. Depending on the ghostscript configuration
"jpeggray"might be available among others. See the output of
gs --helpand the ghostscript documentation for more information.
resolution specifies the resolution in dpi (dots per inch). gs is the name of the ghostscript executable. gsoptions is a list of additional options passed to the ghostscript interpreter. textalphabits and graphicsalphabits are convenient parameters to set the
GraphicsAlphaBitsoptions of ghostscript. The addition of these options can be skipped by setting their values to
None. ciecolor adds the
-dUseCIEColorflag to improve the CMYK to RGB color conversion. input can be either
"pdf"to select the input type to be passed to ghostscript (note slightly different features available in the different input types regarding e.g.
epsfileinclusion and transparency).
kwargs are passed to the
writeEPSfile()method (not counting the file parameter), which is used to generate the input for ghostscript. By that you gain access to the
- canvas.writeGSfile(filename=None, device=None, **kwargs)¶
This method is similar to pipeGS, but the content is written into the file filename. If filename is None it is auto-guessed from the script name. If filename is “-”, the output is written to stdout. In both cases, a device needs to be specified to define the format (and the file suffix in case the filename is created from the script name).
If device is None, but a filename with suffix is given, PNG files will be written using the png16m device and JPG files using the jpeg device.
All other arguments are identical to those of the
In addition the canvas module contains the class
canvas.clip which allows for
clipping of the output by passing a clipping instance to the attrs parameter of
the canvas constructor.