Source code for matplotlib.backends.backend_cairo

A Cairo backend for matplotlib
:Author: Steve Chaplin and others

This backend depends on cairocffi or pycairo.

import gzip
import math

import numpy as np

    import cairo
    if cairo.version_info < (1, 11, 0):
        # Introduced create_for_data for Py3.
        raise ImportError
except ImportError:
        import cairocffi as cairo
    except ImportError as err:
        raise ImportError(
            "cairo backend requires that pycairo>=1.11.0 or cairocffi "
            "is installed") from err

import matplotlib as mpl
from .. import _api, cbook, font_manager
from matplotlib.backend_bases import (
    _Backend, _check_savefig_extra_args, FigureCanvasBase, FigureManagerBase,
    GraphicsContextBase, RendererBase)
from matplotlib.font_manager import ttfFontProperty
from matplotlib.mathtext import MathTextParser
from matplotlib.path import Path
from matplotlib.transforms import Affine2D

backend_version = cairo.version

if cairo.__name__ == "cairocffi":
    # Convert a pycairo context to a cairocffi one.
    def _to_context(ctx):
        if not isinstance(ctx, cairo.Context):
            ctx = cairo.Context._from_pointer(
                    'cairo_t **',
                    id(ctx) + object.__basicsize__)[0],
        return ctx
    # Pass-through a pycairo context.
    def _to_context(ctx):
        return ctx

def _append_path(ctx, path, transform, clip=None):
    for points, code in path.iter_segments(
            transform, remove_nans=True, clip=clip):
        if code == Path.MOVETO:
        elif code == Path.CLOSEPOLY:
        elif code == Path.LINETO:
        elif code == Path.CURVE3:
            cur = np.asarray(ctx.get_current_point())
            a = points[:2]
            b = points[-2:]
            ctx.curve_to(*(cur / 3 + a * 2 / 3), *(a * 2 / 3 + b / 3), *b)
        elif code == Path.CURVE4:

def _cairo_font_args_from_font_prop(prop):
    Convert a `.FontProperties` or a `.FontEntry` to arguments that can be
    passed to `.Context.select_font_face`.
    def attr(field):
            return getattr(prop, f"get_{field}")()
        except AttributeError:
            return getattr(prop, field)

    name = attr("name")
    slant = getattr(cairo, f"FONT_SLANT_{attr('style').upper()}")
    weight = attr("weight")
    weight = (cairo.FONT_WEIGHT_NORMAL
              if font_manager.weight_dict.get(weight, weight) < 550
              else cairo.FONT_WEIGHT_BOLD)
    return name, slant, weight

# Mappings used for deprecated properties in RendererCairo, see below.
_f_weights = {
    100:          cairo.FONT_WEIGHT_NORMAL,
    200:          cairo.FONT_WEIGHT_NORMAL,
    300:          cairo.FONT_WEIGHT_NORMAL,
    400:          cairo.FONT_WEIGHT_NORMAL,
    500:          cairo.FONT_WEIGHT_NORMAL,
    600:          cairo.FONT_WEIGHT_BOLD,
    700:          cairo.FONT_WEIGHT_BOLD,
    800:          cairo.FONT_WEIGHT_BOLD,
    900:          cairo.FONT_WEIGHT_BOLD,
    'ultralight': cairo.FONT_WEIGHT_NORMAL,
    'light':      cairo.FONT_WEIGHT_NORMAL,
    'normal':     cairo.FONT_WEIGHT_NORMAL,
    'medium':     cairo.FONT_WEIGHT_NORMAL,
    'regular':    cairo.FONT_WEIGHT_NORMAL,
    'semibold':   cairo.FONT_WEIGHT_BOLD,
    'bold':       cairo.FONT_WEIGHT_BOLD,
    'heavy':      cairo.FONT_WEIGHT_BOLD,
    'ultrabold':  cairo.FONT_WEIGHT_BOLD,
    'black':      cairo.FONT_WEIGHT_BOLD,
_f_angles = {
    'italic':  cairo.FONT_SLANT_ITALIC,
    'normal':  cairo.FONT_SLANT_NORMAL,
    'oblique': cairo.FONT_SLANT_OBLIQUE,

[docs]class RendererCairo(RendererBase): fontweights = _api.deprecated("3.3")(property(lambda self: {*_f_weights})) fontangles = _api.deprecated("3.3")(property(lambda self: {*_f_angles})) mathtext_parser = _api.deprecated("3.4")( property(lambda self: MathTextParser('Cairo'))) def __init__(self, dpi): self.dpi = dpi self.gc = GraphicsContextCairo(renderer=self) self.text_ctx = cairo.Context( cairo.ImageSurface(cairo.FORMAT_ARGB32, 1, 1)) super().__init__()
[docs] def set_ctx_from_surface(self, surface): self.gc.ctx = cairo.Context(surface)
# Although it may appear natural to automatically call # `self.set_width_height(surface.get_width(), surface.get_height())` # here (instead of having the caller do so separately), this would fail # for PDF/PS/SVG surfaces, which have no way to report their extents.
[docs] def set_width_height(self, width, height): self.width = width self.height = height
def _fill_and_stroke(self, ctx, fill_c, alpha, alpha_overrides): if fill_c is not None: if len(fill_c) == 3 or alpha_overrides: ctx.set_source_rgba(fill_c[0], fill_c[1], fill_c[2], alpha) else: ctx.set_source_rgba(fill_c[0], fill_c[1], fill_c[2], fill_c[3]) ctx.fill_preserve() ctx.restore() ctx.stroke()
[docs] def draw_path(self, gc, path, transform, rgbFace=None): # docstring inherited ctx = gc.ctx # Clip the path to the actual rendering extents if it isn't filled. clip = (ctx.clip_extents() if rgbFace is None and gc.get_hatch() is None else None) transform = (transform + Affine2D().scale(1, -1).translate(0, self.height)) ctx.new_path() _append_path(ctx, path, transform, clip) self._fill_and_stroke( ctx, rgbFace, gc.get_alpha(), gc.get_forced_alpha())
[docs] def draw_markers(self, gc, marker_path, marker_trans, path, transform, rgbFace=None): # docstring inherited ctx = gc.ctx ctx.new_path() # Create the path for the marker; it needs to be flipped here already! _append_path(ctx, marker_path, marker_trans + Affine2D().scale(1, -1)) marker_path = ctx.copy_path_flat() # Figure out whether the path has a fill x1, y1, x2, y2 = ctx.fill_extents() if x1 == 0 and y1 == 0 and x2 == 0 and y2 == 0: filled = False # No fill, just unset this (so we don't try to fill it later on) rgbFace = None else: filled = True transform = (transform + Affine2D().scale(1, -1).translate(0, self.height)) ctx.new_path() for i, (vertices, codes) in enumerate( path.iter_segments(transform, simplify=False)): if len(vertices): x, y = vertices[-2:] # Translate and apply path ctx.translate(x, y) ctx.append_path(marker_path) ctx.restore() # Slower code path if there is a fill; we need to draw # the fill and stroke for each marker at the same time. # Also flush out the drawing every once in a while to # prevent the paths from getting way too long. if filled or i % 1000 == 0: self._fill_and_stroke( ctx, rgbFace, gc.get_alpha(), gc.get_forced_alpha()) # Fast path, if there is no fill, draw everything in one step if not filled: self._fill_and_stroke( ctx, rgbFace, gc.get_alpha(), gc.get_forced_alpha())
[docs] def draw_image(self, gc, x, y, im): im = cbook._unmultiplied_rgba8888_to_premultiplied_argb32(im[::-1]) surface = cairo.ImageSurface.create_for_data( im.ravel().data, cairo.FORMAT_ARGB32, im.shape[1], im.shape[0], im.shape[1] * 4) ctx = gc.ctx y = self.height - y - im.shape[0] ctx.set_source_surface(surface, float(x), float(y)) ctx.paint() ctx.restore()
[docs] def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None): # docstring inherited # Note: (x, y) are device/display coords, not user-coords, unlike other # draw_* methods if ismath: self._draw_mathtext(gc, x, y, s, prop, angle) else: ctx = gc.ctx ctx.new_path() ctx.move_to(x, y) ctx.select_font_face(*_cairo_font_args_from_font_prop(prop)) ctx.set_font_size(prop.get_size_in_points() * self.dpi / 72) opts = cairo.FontOptions() opts.set_antialias( cairo.ANTIALIAS_DEFAULT if mpl.rcParams["text.antialiased"] else cairo.ANTIALIAS_NONE) ctx.set_font_options(opts) if angle: ctx.rotate(np.deg2rad(-angle)) ctx.show_text(s) ctx.restore()
def _draw_mathtext(self, gc, x, y, s, prop, angle): ctx = gc.ctx width, height, descent, glyphs, rects = \ self._text2path.mathtext_parser.parse(s, self.dpi, prop) ctx.translate(x, y) if angle: ctx.rotate(np.deg2rad(-angle)) for font, fontsize, idx, ox, oy in glyphs: ctx.new_path() ctx.move_to(ox, -oy) ctx.select_font_face( *_cairo_font_args_from_font_prop(ttfFontProperty(font))) ctx.set_font_size(fontsize * self.dpi / 72) ctx.show_text(chr(idx)) for ox, oy, w, h in rects: ctx.new_path() ctx.rectangle(ox, -oy, w, -h) ctx.set_source_rgb(0, 0, 0) ctx.fill_preserve() ctx.restore()
[docs] def get_canvas_width_height(self): # docstring inherited return self.width, self.height
[docs] def get_text_width_height_descent(self, s, prop, ismath): # docstring inherited if ismath == 'TeX': return super().get_text_width_height_descent(s, prop, ismath) if ismath: width, height, descent, *_ = \ self._text2path.mathtext_parser.parse(s, self.dpi, prop) return width, height, descent ctx = self.text_ctx # problem - scale remembers last setting and font can become # enormous causing program to crash # save/restore prevents the problem ctx.select_font_face(*_cairo_font_args_from_font_prop(prop)) # Cairo (says it) uses 1/96 inch user space units, ref: cairo_gstate.c # but if /96.0 is used the font is too small ctx.set_font_size(prop.get_size_in_points() * self.dpi / 72) y_bearing, w, h = ctx.text_extents(s)[1:4] ctx.restore() return w, h, h + y_bearing
[docs] def new_gc(self): # docstring inherited self.gc._alpha = 1 self.gc._forced_alpha = False # if True, _alpha overrides A from RGBA return self.gc
[docs] def points_to_pixels(self, points): # docstring inherited return points / 72 * self.dpi
[docs]class GraphicsContextCairo(GraphicsContextBase): _joind = { 'bevel': cairo.LINE_JOIN_BEVEL, 'miter': cairo.LINE_JOIN_MITER, 'round': cairo.LINE_JOIN_ROUND, } _capd = { 'butt': cairo.LINE_CAP_BUTT, 'projecting': cairo.LINE_CAP_SQUARE, 'round': cairo.LINE_CAP_ROUND, } def __init__(self, renderer): super().__init__() self.renderer = renderer
[docs] def restore(self): self.ctx.restore()
[docs] def set_alpha(self, alpha): super().set_alpha(alpha) _alpha = self.get_alpha() rgb = self._rgb if self.get_forced_alpha(): self.ctx.set_source_rgba(rgb[0], rgb[1], rgb[2], _alpha) else: self.ctx.set_source_rgba(rgb[0], rgb[1], rgb[2], rgb[3])
[docs] def set_antialiased(self, b): self.ctx.set_antialias( cairo.ANTIALIAS_DEFAULT if b else cairo.ANTIALIAS_NONE)
[docs] def set_capstyle(self, cs): self.ctx.set_line_cap(_api.check_getitem(self._capd, capstyle=cs)) self._capstyle = cs
[docs] def set_clip_rectangle(self, rectangle): if not rectangle: return x, y, w, h = np.round(rectangle.bounds) ctx = self.ctx ctx.new_path() ctx.rectangle(x, self.renderer.height - h - y, w, h) ctx.clip()
[docs] def set_clip_path(self, path): if not path: return tpath, affine = path.get_transformed_path_and_affine() ctx = self.ctx ctx.new_path() affine = (affine + Affine2D().scale(1, -1).translate(0, self.renderer.height)) _append_path(ctx, tpath, affine) ctx.clip()
[docs] def set_dashes(self, offset, dashes): self._dashes = offset, dashes if dashes is None: self.ctx.set_dash([], 0) # switch dashes off else: self.ctx.set_dash( list(self.renderer.points_to_pixels(np.asarray(dashes))), offset)
[docs] def set_foreground(self, fg, isRGBA=None): super().set_foreground(fg, isRGBA) if len(self._rgb) == 3: self.ctx.set_source_rgb(*self._rgb) else: self.ctx.set_source_rgba(*self._rgb)
[docs] def get_rgb(self): return self.ctx.get_source().get_rgba()[:3]
[docs] def set_joinstyle(self, js): self.ctx.set_line_join(_api.check_getitem(self._joind, joinstyle=js)) self._joinstyle = js
[docs] def set_linewidth(self, w): self._linewidth = float(w) self.ctx.set_line_width(self.renderer.points_to_pixels(w))
class _CairoRegion: def __init__(self, slices, data): self._slices = slices self._data = data
[docs]class FigureCanvasCairo(FigureCanvasBase):
[docs] def copy_from_bbox(self, bbox): surface = self._renderer.gc.ctx.get_target() if not isinstance(surface, cairo.ImageSurface): raise RuntimeError( "copy_from_bbox only works when rendering to an ImageSurface") sw = surface.get_width() sh = surface.get_height() x0 = math.ceil(bbox.x0) x1 = math.floor(bbox.x1) y0 = math.ceil(sh - bbox.y1) y1 = math.floor(sh - bbox.y0) if not (0 <= x0 and x1 <= sw and bbox.x0 <= bbox.x1 and 0 <= y0 and y1 <= sh and bbox.y0 <= bbox.y1): raise ValueError("Invalid bbox") sls = slice(y0, y0 + max(y1 - y0, 0)), slice(x0, x0 + max(x1 - x0, 0)) data = (np.frombuffer(surface.get_data(), np.uint32) .reshape((sh, sw))[sls].copy()) return _CairoRegion(sls, data)
[docs] def restore_region(self, region): surface = self._renderer.gc.ctx.get_target() if not isinstance(surface, cairo.ImageSurface): raise RuntimeError( "restore_region only works when rendering to an ImageSurface") surface.flush() sw = surface.get_width() sh = surface.get_height() sly, slx = region._slices (np.frombuffer(surface.get_data(), np.uint32) .reshape((sh, sw))[sly, slx]) = region._data surface.mark_dirty_rectangle( slx.start, sly.start, slx.stop - slx.start, sly.stop - sly.start)
[docs] @_check_savefig_extra_args def print_png(self, fobj): self._get_printed_image_surface().write_to_png(fobj)
[docs] @_check_savefig_extra_args def print_rgba(self, fobj): width, height = self.get_width_height() buf = self._get_printed_image_surface().get_data() fobj.write(cbook._premultiplied_argb32_to_unmultiplied_rgba8888( np.asarray(buf).reshape((width, height, 4))))
print_raw = print_rgba def _get_printed_image_surface(self): width, height = self.get_width_height() renderer = RendererCairo(self.figure.dpi) renderer.set_width_height(width, height) surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height) renderer.set_ctx_from_surface(surface) self.figure.draw(renderer) return surface
[docs] def print_pdf(self, fobj, *args, **kwargs): return self._save(fobj, 'pdf', *args, **kwargs)
[docs] def print_ps(self, fobj, *args, **kwargs): return self._save(fobj, 'ps', *args, **kwargs)
[docs] def print_svg(self, fobj, *args, **kwargs): return self._save(fobj, 'svg', *args, **kwargs)
[docs] def print_svgz(self, fobj, *args, **kwargs): return self._save(fobj, 'svgz', *args, **kwargs)
@_check_savefig_extra_args def _save(self, fo, fmt, *, orientation='portrait'): # save PDF/PS/SVG dpi = 72 self.figure.dpi = dpi w_in, h_in = self.figure.get_size_inches() width_in_points, height_in_points = w_in * dpi, h_in * dpi if orientation == 'landscape': width_in_points, height_in_points = ( height_in_points, width_in_points) if fmt == 'ps': if not hasattr(cairo, 'PSSurface'): raise RuntimeError('cairo has not been compiled with PS ' 'support enabled') surface = cairo.PSSurface(fo, width_in_points, height_in_points) elif fmt == 'pdf': if not hasattr(cairo, 'PDFSurface'): raise RuntimeError('cairo has not been compiled with PDF ' 'support enabled') surface = cairo.PDFSurface(fo, width_in_points, height_in_points) elif fmt in ('svg', 'svgz'): if not hasattr(cairo, 'SVGSurface'): raise RuntimeError('cairo has not been compiled with SVG ' 'support enabled') if fmt == 'svgz': if isinstance(fo, str): fo = gzip.GzipFile(fo, 'wb') else: fo = gzip.GzipFile(None, 'wb', fileobj=fo) surface = cairo.SVGSurface(fo, width_in_points, height_in_points) else: raise ValueError("Unknown format: {!r}".format(fmt)) # surface.set_dpi() can be used renderer = RendererCairo(self.figure.dpi) renderer.set_width_height(width_in_points, height_in_points) renderer.set_ctx_from_surface(surface) ctx = renderer.gc.ctx if orientation == 'landscape': ctx.rotate(np.pi / 2) ctx.translate(0, -height_in_points) # Perhaps add an '%%Orientation: Landscape' comment? self.figure.draw(renderer) ctx.show_page() surface.finish() if fmt == 'svgz': fo.close()
@_Backend.export class _BackendCairo(_Backend): FigureCanvas = FigureCanvasCairo FigureManager = FigureManagerBase