python-igraph/src/igraph/drawing/cairo/plot.py at main · igraph/python-igraph

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Drawing and plotting routines for IGraph.
igraph has two plotting backends at the moment: Cairo and Matplotlib.
The Cairo backend is dependent on the C{pycairo} or C{cairocffi} libraries that
provide Python bindings to the popular U{Cairo library<http://www.cairographics.org>}.
This means that if you don't have U{pycairo<http://www.cairographics.org/pycairo>}
or U{cairocffi<https://doc.courtbouillon.org/cairocffi/>} installed, you won't be able
to use the Cairo plotting backend. Whenever the documentation refers to the
C{pycairo} library, you can safely replace it with C{cairocffi} as the two are
API-compatible.
The Matplotlib backend uses the U{Matplotlib library<https://matplotlib.org>}.
You will need to install it from PyPI if you want to use the Matplotlib
plotting backend.
If you do not want to (or cannot) install any of the dependencies outlined
above, you can still save the graph to an SVG file and view it from
U{Mozilla Firefox<https://www.mozilla.org/firefox>} (free) or edit it in
U{Inkscape<https://www.inkscape.org>} (free), U{Skencil<https://www.skencil.org>}
(formerly known as Sketch, also free) or Adobe Illustrator.
from io import BytesIO
from warnings import warn
from igraph.configuration import Configuration
from igraph.drawing.cairo.utils import find_cairo
from igraph.drawing.colors import Palette, palettes
from igraph.drawing.utils import BoundingBox
from igraph.utils import named_temporary_file
__all__ = ("CairoPlot",)
cairo = find_cairo()
#####################################################################
class CairoPlot:
    """Class representing an arbitrary plot that uses the Cairo plotting
    backend.
    Objects that you can plot include graphs, matrices, palettes, clusterings,
    covers, and dendrograms.
    In Cairo, every plot has an associated surface object. The surface is an
    instance of C{cairo.Surface}, a member of the C{pycairo} library. The
    surface itself provides a unified API to various plotting targets like SVG
    files, X11 windows, PostScript files, PNG files and so on. C{igraph} does
    not usually know on which surface it is plotting at each point in time,
    since C{pycairo} takes care of the actual drawing. Everything that's
    supported by C{pycairo} should be supported by this class as well.
    Current Cairo surfaces include:
      - C{cairo.GlitzSurface} -- OpenGL accelerated surface for the X11
        Window System.
      - C{cairo.ImageSurface} -- memory buffer surface. Can be written to a
        C{PNG} image file.
      - C{cairo.PDFSurface} -- PDF document surface.
      - C{cairo.PSSurface} -- PostScript document surface.
      - C{cairo.SVGSurface} -- SVG (Scalable Vector Graphics) document surface.
      - C{cairo.Win32Surface} -- Microsoft Windows screen rendering.
      - C{cairo.XlibSurface} -- X11 Window System screen rendering.
    If you create a C{Plot} object with a string given as the target surface,
    the string will be treated as a filename, and its extension will decide
    which surface class will be used. Please note that not all surfaces might
    be available, depending on your C{pycairo} installation.
    A C{Plot} has an assigned default palette (see L{igraph.drawing.colors.Palette})
    which is used for plotting objects.
    A C{Plot} object also has a list of objects to be plotted with their
    respective bounding boxes, palettes and opacities. Palettes assigned to an
    object override the default palette of the plot. Objects can be added by the
    L{Plot.add} method and removed by the L{Plot.remove} method.
    def __init__(
        self,
        target=None,
        bbox=None,
        palette=None,
        background=None,
        """Creates a new plot.
        @param target: the target surface to write to. It can be one of the
          following types:
            - C{None} -- a Cairo surface will be created and the object will be
              plotted there.
            - C{cairo.Surface} -- the given Cairo surface will be used.
            - C{string} -- a file with the given name will be created and an
              appropriate Cairo surface will be attached to it.
        @param bbox: the bounding box of the surface. It is interpreted
          differently with different surfaces: PDF and PS surfaces will treat it
          as points (1 point = 1/72 inch). Image surfaces will treat it as
          pixels. SVG surfaces will treat it as an abstract unit, but it will
          mostly be interpreted as pixels when viewing the SVG file in Firefox.
        @param palette: the palette primarily used on the plot if the
          added objects do not specify a private palette. Must be either
          an L{igraph.drawing.colors.Palette} object or a string referring
          to a valid key of C{igraph.drawing.colors.palettes} (see module
          L{igraph.drawing.colors}) or C{None}. In the latter case, the default
          palette given by the configuration key C{plotting.palette} is used.
        @param background: the background color. If C{None}, the background
          will be transparent. You can use any color specification here that is
          understood by L{igraph.drawing.colors.color_name_to_rgba}.
        """
        self._filename = None
        self._need_tmpfile = False
        if bbox is None:
            self.bbox = BoundingBox(600, 600)
        elif isinstance(bbox, tuple) or isinstance(bbox, list):
            self.bbox = BoundingBox(bbox)
        else:
            self.bbox = bbox
        if palette is None:
            config = Configuration.instance()
            palette = config["plotting.palette"]
        if not isinstance(palette, Palette):
            palette = palettes[palette]
        self._palette = palette
        if target is None:
            self._need_tmpfile = True
            self._surface = cairo.ImageSurface(
                cairo.FORMAT_ARGB32, int(self.bbox.width), int(self.bbox.height)
        elif isinstance(target, cairo.Surface):
            self._surface = target
        else:
            self._filename = target
            _, ext = os.path.splitext(target)
            ext = ext.lower()
            if ext == ".pdf":
                self._surface = cairo.PDFSurface(
                    target, self.bbox.width, self.bbox.height
            elif ext == ".ps" or ext == ".eps":
                self._surface = cairo.PSSurface(
                    target, self.bbox.width, self.bbox.height
            elif ext == ".png":
                self._surface = cairo.ImageSurface(
                    cairo.FORMAT_ARGB32, int(self.bbox.width), int(self.bbox.height)
            elif ext == ".svg":
                self._surface = cairo.SVGSurface(
                    target, self.bbox.width, self.bbox.height
            else:
                raise ValueError("image format not handled by Cairo: %s" % ext)
        self._ctx = cairo.Context(self._surface)
        self._objects = []
        self._is_dirty = False
        if background is None:
            background = "white"
        self.background = background
    def add(self, obj, bbox=None, palette=None, opacity=1.0, *args, **kwds):
        """Adds an object to the plot.
        Arguments not specified here are stored and passed to the object's
        plotting function when necessary. Since you are most likely interested
        in the arguments acceptable by graphs, see L{Graph.__plot__} for more
        details.
        @param obj: the object to be added
        @param bbox: the bounding box of the object. If C{None}, the object
          will fill the entire area of the plot.
        @param palette: the color palette used for drawing the object. If the
          object tries to get a color assigned to a positive integer, it
          will use this palette. If C{None}, defaults to the global palette
          of the plot.
        @param opacity: the opacity of the object being plotted, in the range
        @see: Graph.__plot__
        """
        if opacity < 0.0 or opacity > 1.0:
            raise ValueError("opacity must be between 0.0 and 1.0")
        if bbox is None:
            bbox = self.bbox
        if (bbox is not None) and (not isinstance(bbox, BoundingBox)):
            bbox = BoundingBox(bbox)
        self._objects.append((obj, bbox, palette, opacity, args, kwds))
        self.mark_dirty()
    @property
    def background(self):
        """Returns the background color of the plot. C{None} means a
        transparent background.
        """
        return self._background
    @background.setter
    def background(self, color):
        """Sets the background color of the plot. C{None} means a
        transparent background. You can use any color specification here
        that is understood by the C{get} method of the current palette
        or by L{igraph.drawing.colors.color_name_to_rgb}.
        """
        if color is None:
            self._background = None
        else:
            self._background = self._palette.get(color)
    def remove(self, obj, bbox=None, idx=1):
        """Removes an object from the plot.
        If the object has been added multiple times and no bounding box
        was specified, it removes the instance which occurs M{idx}th
        in the list of identical instances of the object.
        @param obj: the object to be removed
        @param bbox: optional bounding box specification for the object.
          If given, only objects with exactly this bounding box will be
          considered.
        @param idx: if multiple objects match the specification given by
          M{obj} and M{bbox}, only the M{idx}th occurrence will be removed.
        @return: C{True} if the object has been removed successfully,
          C{False} if the object was not on the plot at all or M{idx}
          was larger than the count of occurrences
        """
        for i in range(len(self._objects)):
            current_obj, current_bbox = self._objects[i][0:2]
            if current_obj is obj and (bbox is None or current_bbox == bbox):
                idx -= 1
                if idx == 0:
                    self._objects[i : (i + 1)] = []
                    self.mark_dirty()
                    return True
        return False
    def mark_dirty(self):
        """Marks the plot as dirty (should be redrawn)"""
        self._is_dirty = True
    def redraw(self, context=None):
        """Redraws the plot"""
        ctx = context or self._ctx
        if self._background is not None:
            ctx.set_source_rgba(*self._background)
            ctx.rectangle(0, 0, self.bbox.width, self.bbox.height)
            ctx.fill()
        for obj, bbox, palette, opacity, args, kwds in self._objects:
            if palette is None:
                palette = getattr(obj, "_default_palette", self._palette)
            plotter = getattr(obj, "__plot__", None)
            if plotter is None:
                warn("%s does not support plotting" % (obj,), stacklevel=1)
            else:
                if opacity < 1.0:
                    ctx.push_group()
                else:
                    ctx.save()
                plotter(
                    "cairo",
                    bbox=bbox,
                    palette=palette,
                    *args,  # noqa: B026
                    **kwds,
                if opacity < 1.0:
                    ctx.pop_group_to_source()
                    ctx.paint_with_alpha(opacity)
                else:
                    ctx.restore()
        self._is_dirty = False
    def save(self, fname=None):
        """Saves the plot.
        @param fname: the filename to save to. It is ignored if the surface
          of the plot is not an C{ImageSurface}.
        """
        if self._is_dirty:
            self.redraw()
        if isinstance(self._surface, cairo.ImageSurface):
            if fname is None and self._need_tmpfile:
                with named_temporary_file(prefix="igraph", suffix=".png") as fname:
                    self._surface.write_to_png(fname)
                    return None
            fname = fname or self._filename
            if fname is None:
                raise ValueError("no file name is known for the surface and none given")
            # Conversion to string is needed because the user might pass a Path
            # object and cairocffi expects a string
            return self._surface.write_to_png(str(fname))
        if fname is not None:
            warn(
                "filename is ignored for surfaces other than ImageSurface", stacklevel=1
        self._ctx.show_page()
        self._surface.finish()
    def _repr_svg_(self):
        """Returns an SVG representation of this plot as a string.
        This method is used by IPython to display this plot inline.
        """
        io = BytesIO()
        # Create a new SVG surface and use that to get the SVG representation,
        # which will end up in io
        surface = cairo.SVGSurface(io, self.bbox.width, self.bbox.height)
        context = cairo.Context(surface)
        # Plot the graph on this context
        self.redraw(context)
        # No idea why this is needed but python crashes without
        context.show_page()
        surface.finish()
        # Return the raw SVG representation
        result = io.getvalue().decode("utf-8")
        return result, {"isolated": True}  # put it inside an iframe
    @property
    def bounding_box(self):
        """Returns the bounding box of the Cairo surface as a
        L{BoundingBox} object"""
        return BoundingBox(self.bbox)
    @property
    def height(self):
        """Returns the height of the Cairo surface on which the plot
        is drawn"""
        return self.bbox.height
    @property
    def surface(self):
        """Returns the Cairo surface on which the plot is drawn"""
        return self._surface
    @property
    def width(self):
        """Returns the width of the Cairo surface on which the plot
        is drawn"""
        return self.bbox.width
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