Repo re-org, make gerberex tests run

1 files changed, 616 insertions, 0 deletions

diff --git a/gerbonara/gerber/render/cairo_backend.py b/gerbonara/gerber/render/cairo_backend.py
new file mode 100644
index 0000000..e1d1408
--- /dev/null
+++ b/gerbonara/gerber/render/cairo_backend.py
@@ -0,0 +1,616 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# Copyright 2014 Hamilton Kibbe <ham@hamiltonkib.be>
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+try:
+    import cairo
+except ImportError:
+    import cairocffi as cairo
+
+from operator import mul
+import tempfile
+import copy
+import os
+
+from .render import GerberContext, RenderSettings
+from .theme import THEMES
+from ..primitives import *
+from ..utils import rotate_point
+
+from io import BytesIO
+
+
+class GerberCairoContext(GerberContext):
+
+    def __init__(self, scale=300):
+        super(GerberCairoContext, self).__init__()
+        self.scale = (scale, scale)
+        self.surface = None
+        self.surface_buffer = None
+        self.ctx = None
+        self.active_layer = None
+        self.active_matrix = None
+        self.output_ctx = None
+        self.has_bg = False
+        self.origin_in_inch = None
+        self.size_in_inch = None
+        self._xform_matrix = None
+        self._render_count = 0
+
+    @property
+    def origin_in_pixels(self):
+        return (self.scale_point(self.origin_in_inch)
+                if self.origin_in_inch is not None else (0.0, 0.0))
+
+    @property
+    def size_in_pixels(self):
+        return (self.scale_point(self.size_in_inch)
+                if self.size_in_inch is not None else (0.0, 0.0))
+
+    def set_bounds(self, bounds, new_surface=False):
+        origin_in_inch = (bounds[0][0], bounds[1][0])
+        size_in_inch = (abs(bounds[0][1] - bounds[0][0]),
+                        abs(bounds[1][1] - bounds[1][0]))
+        size_in_pixels = self.scale_point(size_in_inch)
+        self.origin_in_inch = origin_in_inch if self.origin_in_inch is None else self.origin_in_inch
+        self.size_in_inch = size_in_inch if self.size_in_inch is None else self.size_in_inch
+        self._xform_matrix = cairo.Matrix(xx=1.0, yy=-1.0,
+                                          x0=-self.origin_in_pixels[0],
+                                          y0=self.size_in_pixels[1])
+        if (self.surface is None) or new_surface:
+            self.surface_buffer = tempfile.NamedTemporaryFile()
+            self.surface = cairo.SVGSurface(self.surface_buffer, size_in_pixels[0], size_in_pixels[1])
+            self.output_ctx = cairo.Context(self.surface)
+
+    def render_layer(self, layer, filename=None, settings=None, bgsettings=None,
+                     verbose=False, bounds=None):
+        if settings is None:
+            settings = THEMES['default'].get(layer.layer_class, RenderSettings())
+        if bgsettings is None:
+            bgsettings = THEMES['default'].get('background', RenderSettings())
+
+        if self._render_count == 0:
+            if verbose:
+                print('[Render]: Rendering Background.')
+            self.clear()
+            if bounds is not None:
+                self.set_bounds(bounds)
+            else:
+                self.set_bounds(layer.bounds)
+            self.paint_background(bgsettings)
+        if verbose:
+            print('[Render]: Rendering {} Layer.'.format(layer.layer_class))
+        self._render_count += 1
+        self._render_layer(layer, settings)
+        if filename is not None:
+            self.dump(filename, verbose)
+
+    def render_layers(self, layers, filename, theme=THEMES['default'],
+                      verbose=False, max_width=800, max_height=600):
+        """ Render a set of layers
+        """
+        # Calculate scale parameter
+        x_range = [10000, -10000]
+        y_range = [10000, -10000]
+        for layer in layers:
+            bounds = layer.bounds
+            if bounds is not None:
+                layer_x, layer_y = bounds
+                x_range[0] = min(x_range[0], layer_x[0])
+                x_range[1] = max(x_range[1], layer_x[1])
+                y_range[0] = min(y_range[0], layer_y[0])
+                y_range[1] = max(y_range[1], layer_y[1])
+        width = x_range[1] - x_range[0]
+        height = y_range[1] - y_range[0]
+
+        scale = math.floor(min(float(max_width)/width, float(max_height)/height))
+        self.scale = (scale, scale)
+
+        self.clear()
+
+        # Render layers
+        bgsettings = theme['background']
+        for layer in layers:
+            settings = theme.get(layer.layer_class, RenderSettings())
+            self.render_layer(layer, settings=settings, bgsettings=bgsettings,
+                              verbose=verbose)
+        self.dump(filename, verbose)
+
+    def dump(self, filename=None, verbose=False):
+        """ Save image as `filename`
+        """
+        try:
+            is_svg = os.path.splitext(filename.lower())[1] == '.svg'
+        except:
+            is_svg = False
+        if verbose:
+            print('[Render]: Writing image to {}'.format(filename))
+        if is_svg:
+            self.surface.finish()
+            self.surface_buffer.flush()
+            with open(filename, "wb") as f:
+                self.surface_buffer.seek(0)
+                f.write(self.surface_buffer.read())
+                f.flush()
+        else:
+            return self.surface.write_to_png(filename)
+
+    def dump_str(self):
+        """ Return a byte-string containing the rendered image.
+        """
+        fobj = BytesIO()
+        self.surface.write_to_png(fobj)
+        return fobj.getvalue()
+
+    def dump_svg_str(self):
+        """ Return a string containg the rendered SVG.
+        """
+        self.surface.finish()
+        self.surface_buffer.flush()
+        return self.surface_buffer.read()
+
+    def clear(self):
+        self.surface = None
+        self.output_ctx = None
+        self.has_bg = False
+        self.origin_in_inch = None
+        self.size_in_inch = None
+        self._xform_matrix = None
+        self._render_count = 0
+        self.surface_buffer = None
+
+    def _new_mask(self):
+        class Mask:
+            def __enter__(msk):
+                size_in_pixels = self.size_in_pixels
+                msk.surface = cairo.SVGSurface(None, size_in_pixels[0],
+                                               size_in_pixels[1])
+                msk.ctx = cairo.Context(msk.surface)
+                msk.ctx.translate(-self.origin_in_pixels[0], -self.origin_in_pixels[1])
+                return msk
+
+
+            def __exit__(msk, exc_type, exc_val, traceback):
+                if hasattr(msk.surface, 'finish'):
+                    msk.surface.finish()
+
+        return Mask()
+
+    def _render_layer(self, layer, settings):
+        self.invert = settings.invert
+        # Get a new clean layer to render on
+        self.new_render_layer(mirror=settings.mirror)
+        for prim in layer.primitives:
+            self.render(prim)
+        # Add layer to image
+        self.flatten(settings.color, settings.alpha)
+
+    def _render_line(self, line, color):
+        start = self.scale_point(line.start)
+        end = self.scale_point(line.end)
+        self.ctx.set_operator(cairo.OPERATOR_OVER
+                              if (not self.invert)
+                                 and line.level_polarity == 'dark'
+                              else cairo.OPERATOR_CLEAR)
+
+        with self._clip_primitive(line):
+            with self._new_mask() as mask:
+                if isinstance(line.aperture, Circle):
+                    width = line.aperture.diameter
+                    mask.ctx.set_line_width(width * self.scale[0])
+                    mask.ctx.set_line_cap(cairo.LINE_CAP_ROUND)
+                    mask.ctx.move_to(*start)
+                    mask.ctx.line_to(*end)
+                    mask.ctx.stroke()
+
+                elif hasattr(line, 'vertices') and line.vertices is not None:
+                    points = [self.scale_point(x) for x in line.vertices]
+                    mask.ctx.set_line_width(0)
+                    mask.ctx.move_to(*points[-1])
+                    for point in points:
+                        mask.ctx.line_to(*point)
+                    mask.ctx.fill()
+                self.ctx.mask_surface(mask.surface, self.origin_in_pixels[0])
+
+    def _render_arc(self, arc, color):
+        center = self.scale_point(arc.center)
+        start = self.scale_point(arc.start)
+        end = self.scale_point(arc.end)
+        radius = self.scale[0] * arc.radius
+        two_pi = 2 * math.pi
+        angle1 = (arc.start_angle + two_pi) % two_pi
+        angle2 = (arc.end_angle + two_pi) % two_pi
+        if angle1 == angle2 and arc.quadrant_mode != 'single-quadrant':
+            # Make the angles slightly different otherwise Cario will draw nothing
+            angle2 -= 0.000000001
+        if isinstance(arc.aperture, Circle):
+            width = arc.aperture.diameter if arc.aperture.diameter != 0 else 0.001
+        else:
+            width = max(arc.aperture.width, arc.aperture.height, 0.001)
+
+        self.ctx.set_operator(cairo.OPERATOR_OVER
+                              if (not self.invert)
+                                 and arc.level_polarity == 'dark'
+                              else cairo.OPERATOR_CLEAR)
+        with self._clip_primitive(arc):
+            with self._new_mask() as mask:
+                mask.ctx.set_line_width(width * self.scale[0])
+                mask.ctx.set_line_cap(cairo.LINE_CAP_ROUND if isinstance(arc.aperture, Circle) else cairo.LINE_CAP_SQUARE)
+                mask.ctx.move_to(*start)  # You actually have to do this...
+                if arc.direction == 'counterclockwise':
+                    mask.ctx.arc(center[0], center[1], radius, angle1, angle2)
+                else:
+                    mask.ctx.arc_negative(center[0], center[1], radius,
+                                          angle1, angle2)
+                mask.ctx.move_to(*end)  # ...lame
+                mask.ctx.stroke()
+
+                #if isinstance(arc.aperture, Rectangle):
+                #    print("Flash Rectangle Ends")
+                #    print(arc.aperture.rotation * 180/math.pi)
+                #    rect = arc.aperture
+                #    width = self.scale[0] * rect.width
+                #    height = self.scale[1] * rect.height
+                #    for point, angle in zip((start, end), (angle1, angle2)):
+                #        print("{} w {} h{}".format(point, rect.width, rect.height))
+                #        mask.ctx.rectangle(point[0] - width/2.0,
+                #                           point[1] - height/2.0, width, height)
+                #        mask.ctx.fill()
+
+                self.ctx.mask_surface(mask.surface, self.origin_in_pixels[0])
+
+    def _render_region(self, region, color):
+        self.ctx.set_operator(cairo.OPERATOR_OVER
+                              if (not self.invert) and region.level_polarity == 'dark'
+                              else cairo.OPERATOR_CLEAR)
+        with self._clip_primitive(region):
+            with self._new_mask() as mask:
+                mask.ctx.set_line_width(0)
+                mask.ctx.set_line_cap(cairo.LINE_CAP_ROUND)
+                mask.ctx.move_to(*self.scale_point(region.primitives[0].start))
+                for prim in region.primitives:
+                    if isinstance(prim, Line):
+                        mask.ctx.line_to(*self.scale_point(prim.end))
+                    else:
+                        center = self.scale_point(prim.center)
+                        radius = self.scale[0] * prim.radius
+                        angle1 = prim.start_angle
+                        angle2 = prim.end_angle
+                        if prim.direction == 'counterclockwise':
+                            mask.ctx.arc(center[0], center[1], radius,
+                                         angle1, angle2)
+                        else:
+                            mask.ctx.arc_negative(center[0], center[1], radius,
+                                                  angle1, angle2)
+                mask.ctx.fill()
+                self.ctx.mask_surface(mask.surface, self.origin_in_pixels[0])
+
+    def _render_circle(self, circle, color):
+        center = self.scale_point(circle.position)
+        self.ctx.set_operator(cairo.OPERATOR_OVER
+                              if (not self.invert)
+                                 and circle.level_polarity == 'dark'
+                              else cairo.OPERATOR_CLEAR)
+        with self._clip_primitive(circle):
+            with self._new_mask() as mask:
+                mask.ctx.set_line_width(0)
+                mask.ctx.arc(center[0], center[1], (circle.radius * self.scale[0]), 0, (2 * math.pi))
+                mask.ctx.fill()
+
+                if hasattr(circle, 'hole_diameter') and circle.hole_diameter is not None and circle.hole_diameter > 0:
+                    mask.ctx.set_operator(cairo.OPERATOR_CLEAR)
+                    mask.ctx.arc(center[0], center[1], circle.hole_radius * self.scale[0], 0, 2 * math.pi)
+                    mask.ctx.fill()
+
+                if (hasattr(circle, 'hole_width') and hasattr(circle, 'hole_height')
+                        and circle.hole_width is not None and circle.hole_height is not None
+                        and circle.hole_width > 0 and circle.hole_height > 0):
+                    mask.ctx.set_operator(cairo.OPERATOR_CLEAR
+                                          if circle.level_polarity == 'dark'
+                                             and (not self.invert)
+                                          else cairo.OPERATOR_OVER)
+                    width, height = self.scale_point((circle.hole_width, circle.hole_height))
+                    lower_left = rotate_point(
+                        (center[0] - width / 2.0, center[1] - height / 2.0),
+                                              circle.rotation, center)
+                    lower_right = rotate_point((center[0] + width / 2.0, center[1] - height / 2.0),
+                                               circle.rotation, center)
+                    upper_left = rotate_point((center[0] - width / 2.0, center[1] + height / 2.0),
+                                              circle.rotation, center)
+                    upper_right = rotate_point((center[0] + width / 2.0, center[1] + height / 2.0),
+                                               circle.rotation, center)
+                    points = (lower_left, lower_right, upper_right, upper_left)
+                    mask.ctx.move_to(*points[-1])
+                    for point in points:
+                        mask.ctx.line_to(*point)
+                    mask.ctx.fill()
+                self.ctx.mask_surface(mask.surface, self.origin_in_pixels[0])
+
+    def _render_rectangle(self, rectangle, color):
+        lower_left = self.scale_point(rectangle.lower_left)
+        width, height = tuple([abs(coord) for coord in
+                               self.scale_point((rectangle.width,
+                                                 rectangle.height))])
+        self.ctx.set_operator(cairo.OPERATOR_OVER
+                              if (not self.invert)
+                                 and rectangle.level_polarity == 'dark'
+                              else cairo.OPERATOR_CLEAR)
+        with self._clip_primitive(rectangle):
+            with self._new_mask() as mask:
+                mask.ctx.set_line_width(0)
+                mask.ctx.rectangle(lower_left[0], lower_left[1], width, height)
+                mask.ctx.fill()
+
+                center = self.scale_point(rectangle.position)
+                if rectangle.hole_diameter > 0:
+                    # Render the center clear
+                    mask.ctx.set_operator(cairo.OPERATOR_CLEAR
+                                          if rectangle.level_polarity == 'dark'
+                                             and (not self.invert)
+                                          else cairo.OPERATOR_OVER)
+
+                    mask.ctx.arc(center[0], center[1], rectangle.hole_radius * self.scale[0], 0, 2 * math.pi)
+                    mask.ctx.fill()
+
+                if rectangle.hole_width > 0 and rectangle.hole_height > 0:
+                    mask.ctx.set_operator(cairo.OPERATOR_CLEAR
+                                          if rectangle.level_polarity == 'dark'
+                                             and (not self.invert)
+                                          else cairo.OPERATOR_OVER)
+                    width, height = self.scale_point((rectangle.hole_width, rectangle.hole_height))
+                    lower_left = rotate_point((center[0] - width/2.0, center[1] - height/2.0), rectangle.rotation, center)
+                    lower_right = rotate_point((center[0] + width/2.0, center[1] - height/2.0), rectangle.rotation, center)
+                    upper_left = rotate_point((center[0] - width / 2.0, center[1] + height / 2.0), rectangle.rotation, center)
+                    upper_right = rotate_point((center[0] + width / 2.0, center[1] + height / 2.0), rectangle.rotation, center)
+                    points = (lower_left, lower_right, upper_right, upper_left)
+                    mask.ctx.move_to(*points[-1])
+                    for point in points:
+                        mask.ctx.line_to(*point)
+                    mask.ctx.fill()
+                self.ctx.mask_surface(mask.surface, self.origin_in_pixels[0])
+
+    def _render_obround(self, obround, color):
+        self.ctx.set_operator(cairo.OPERATOR_OVER
+                              if (not self.invert)
+                                 and obround.level_polarity == 'dark'
+                              else cairo.OPERATOR_CLEAR)
+        with self._clip_primitive(obround):
+            with self._new_mask() as mask:
+                mask.ctx.set_line_width(0)
+
+                # Render circles
+                for circle in (obround.subshapes['circle1'], obround.subshapes['circle2']):
+                    center = self.scale_point(circle.position)
+                    mask.ctx.arc(center[0], center[1], (circle.radius * self.scale[0]), 0, (2 * math.pi))
+                    mask.ctx.fill()
+
+                # Render Rectangle
+                rectangle = obround.subshapes['rectangle']
+                lower_left = self.scale_point(rectangle.lower_left)
+                width, height = tuple([abs(coord) for coord in
+                                       self.scale_point((rectangle.width,
+                                                         rectangle.height))])
+                mask.ctx.rectangle(lower_left[0], lower_left[1], width, height)
+                mask.ctx.fill()
+
+                center = self.scale_point(obround.position)
+                if obround.hole_diameter > 0:
+                    # Render the center clear
+                    mask.ctx.set_operator(cairo.OPERATOR_CLEAR)
+                    mask.ctx.arc(center[0], center[1], obround.hole_radius * self.scale[0], 0, 2 * math.pi)
+                    mask.ctx.fill()
+
+                if obround.hole_width > 0 and obround.hole_height > 0:
+                    mask.ctx.set_operator(cairo.OPERATOR_CLEAR
+                                          if rectangle.level_polarity == 'dark'
+                                             and (not self.invert)
+                                          else cairo.OPERATOR_OVER)
+                    width, height =self.scale_point((obround.hole_width, obround.hole_height))
+                    lower_left = rotate_point((center[0] - width / 2.0, center[1] - height / 2.0),
+                                              obround.rotation, center)
+                    lower_right = rotate_point((center[0] + width / 2.0, center[1] - height / 2.0),
+                                               obround.rotation, center)
+                    upper_left = rotate_point((center[0] - width / 2.0, center[1] + height / 2.0),
+                                              obround.rotation, center)
+                    upper_right = rotate_point((center[0] + width / 2.0, center[1] + height / 2.0),
+                                               obround.rotation, center)
+                    points = (lower_left, lower_right, upper_right, upper_left)
+                    mask.ctx.move_to(*points[-1])
+                    for point in points:
+                        mask.ctx.line_to(*point)
+                    mask.ctx.fill()
+
+                self.ctx.mask_surface(mask.surface, self.origin_in_pixels[0])
+
+    def _render_polygon(self, polygon, color):
+        self.ctx.set_operator(cairo.OPERATOR_OVER
+                              if (not self.invert)
+                                 and polygon.level_polarity == 'dark'
+                              else cairo.OPERATOR_CLEAR)
+        with self._clip_primitive(polygon):
+            with self._new_mask() as mask:
+
+                vertices = polygon.vertices
+                mask.ctx.set_line_width(0)
+                mask.ctx.set_line_cap(cairo.LINE_CAP_ROUND)
+                # Start from before the end so it is easy to iterate and make sure
+                # it is closed
+                mask.ctx.move_to(*self.scale_point(vertices[-1]))
+                for v in vertices:
+                    mask.ctx.line_to(*self.scale_point(v))
+                mask.ctx.fill()
+
+                center = self.scale_point(polygon.position)
+                if polygon.hole_radius > 0:
+                    # Render the center clear
+                    mask.ctx.set_operator(cairo.OPERATOR_CLEAR
+                                          if polygon.level_polarity == 'dark'
+                                             and (not self.invert)
+                                          else cairo.OPERATOR_OVER)
+                    mask.ctx.set_line_width(0)
+                    mask.ctx.arc(center[0],
+                                 center[1],
+                                 polygon.hole_radius * self.scale[0], 0, 2 * math.pi)
+                    mask.ctx.fill()
+
+                if polygon.hole_width > 0 and polygon.hole_height > 0:
+                    mask.ctx.set_operator(cairo.OPERATOR_CLEAR
+                                          if polygon.level_polarity == 'dark'
+                                             and (not self.invert)
+                                          else cairo.OPERATOR_OVER)
+                    width, height = self.scale_point((polygon.hole_width, polygon.hole_height))
+                    lower_left = rotate_point((center[0] - width / 2.0, center[1] - height / 2.0),
+                                              polygon.rotation, center)
+                    lower_right = rotate_point((center[0] + width / 2.0, center[1] - height / 2.0),
+                                               polygon.rotation, center)
+                    upper_left = rotate_point((center[0] - width / 2.0, center[1] + height / 2.0),
+                                              polygon.rotation, center)
+                    upper_right = rotate_point((center[0] + width / 2.0, center[1] + height / 2.0),
+                                               polygon.rotation, center)
+                    points = (lower_left, lower_right, upper_right, upper_left)
+                    mask.ctx.move_to(*points[-1])
+                    for point in points:
+                        mask.ctx.line_to(*point)
+                    mask.ctx.fill()
+
+                self.ctx.mask_surface(mask.surface, self.origin_in_pixels[0])
+
+    def _render_drill(self, circle, color=None):
+        color = color if color is not None else self.drill_color
+        self._render_circle(circle, color)
+
+    def _render_slot(self, slot, color):
+        start = map(mul, slot.start, self.scale)
+        end = map(mul, slot.end, self.scale)
+
+        width = slot.diameter
+
+        self.ctx.set_operator(cairo.OPERATOR_OVER
+                              if slot.level_polarity == 'dark' and
+                                 (not self.invert) else cairo.OPERATOR_CLEAR)
+        with self._clip_primitive(slot):
+            with self._new_mask() as mask:
+                mask.ctx.set_line_width(width * self.scale[0])
+                mask.ctx.set_line_cap(cairo.LINE_CAP_ROUND)
+                mask.ctx.move_to(*start)
+                mask.ctx.line_to(*end)
+                mask.ctx.stroke()
+                self.ctx.mask_surface(mask.surface, self.origin_in_pixels[0])
+
+    def _render_amgroup(self, amgroup, color):
+        for primitive in amgroup.primitives:
+            self.render(primitive)
+
+    def _render_test_record(self, primitive, color):
+        position = [pos + origin for pos, origin in
+                    zip(primitive.position, self.origin_in_inch)]
+        self.ctx.select_font_face(
+            'monospace', cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD)
+        self.ctx.set_font_size(13)
+        self._render_circle(Circle(position, 0.015), color)
+        self.ctx.set_operator(cairo.OPERATOR_OVER
+                              if primitive.level_polarity == 'dark' and
+                              (not self.invert) else cairo.OPERATOR_CLEAR)
+        self.ctx.move_to(*[self.scale[0] * (coord + 0.015) for coord in position])
+        self.ctx.scale(1, -1)
+        self.ctx.show_text(primitive.net_name)
+        self.ctx.scale(1, -1)
+
+    def new_render_layer(self, color=None, mirror=False):
+        size_in_pixels = self.scale_point(self.size_in_inch)
+        matrix = copy.copy(self._xform_matrix)
+        layer = cairo.SVGSurface(None, size_in_pixels[0], size_in_pixels[1])
+        ctx = cairo.Context(layer)
+
+        if self.invert:
+            ctx.set_source_rgba(0.0, 0.0, 0.0, 1.0)
+            ctx.set_operator(cairo.OPERATOR_OVER)
+            ctx.paint()
+        if mirror:
+            matrix.xx = -1.0
+            matrix.x0 = self.origin_in_pixels[0] + self.size_in_pixels[0]
+        self.ctx = ctx
+        self.ctx.set_matrix(matrix)
+        self.active_layer = layer
+        self.active_matrix = matrix
+
+    def flatten(self, color=None, alpha=None):
+        color = color if color is not None else self.color
+        alpha = alpha if alpha is not None else self.alpha
+        self.output_ctx.set_source_rgba(color[0], color[1], color[2], alpha)
+        self.output_ctx.mask_surface(self.active_layer)
+        self.ctx = None
+        self.active_layer = None
+        self.active_matrix = None
+
+    def paint_background(self, settings=None):
+        color = settings.color if settings is not None else self.background_color
+        alpha = settings.alpha if settings is not None else 1.0
+        if not self.has_bg:
+            self.has_bg = True
+            self.output_ctx.set_source_rgba(color[0], color[1], color[2], alpha)
+            self.output_ctx.paint()
+
+    def _clip_primitive(self, primitive):
+        """ Clip rendering context to pixel-aligned bounding box
+
+        Calculates pixel- and axis- aligned bounding box, and clips current
+        context to that region. Improves rendering speed significantly. This
+        returns a context manager, use as follows:
+
+            with self._clip_primitive(some_primitive):
+                do_rendering_stuff()
+                do_more_rendering stuff(with, arguments)
+
+        The context manager will reset the context's clipping region when it
+        goes out of scope.
+
+        """
+        class Clip:
+            def __init__(clp, primitive):
+                x_range, y_range = primitive.bounding_box
+                xmin, xmax = x_range
+                ymin, ymax = y_range
+
+                # Round bounds to the nearest pixel outside of the primitive
+                clp.xmin = math.floor(self.scale[0] * xmin)
+                clp.xmax = math.ceil(self.scale[0] * xmax)
+
+                # We need to offset Y to take care of the difference in y-pos
+                # caused by flipping the axis.
+                clp.ymin = math.floor(
+                    (self.scale[1] * ymin) - math.ceil(self.origin_in_pixels[1]))
+                clp.ymax = math.floor(
+                    (self.scale[1] * ymax) - math.floor(self.origin_in_pixels[1]))
+
+                # Calculate width and height, rounded to the nearest pixel
+                clp.width = abs(clp.xmax - clp.xmin)
+                clp.height = abs(clp.ymax - clp.ymin)
+
+            def __enter__(clp):
+                # Clip current context to primitive's bounding box
+                self.ctx.rectangle(clp.xmin, clp.ymin, clp.width, clp.height)
+                self.ctx.clip()
+
+            def __exit__(clp, exc_type, exc_val, traceback):
+                # Reset context clip region
+                self.ctx.reset_clip()
+
+        return Clip(primitive)
+
+    def scale_point(self, point):
+        return tuple([coord * scale for coord, scale in zip(point, self.scale)])