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from matplotlib._image import frombuffer
from matplotlib.backends.backend_agg import RendererAgg
from matplotlib.tight_bbox import process_figure_for_rasterizing
class MixedModeRenderer(object):
"""
A helper class to implement a renderer that switches between
vector and raster drawing. An example may be a PDF writer, where
most things are drawn with PDF vector commands, but some very
complex objects, such as quad meshes, are rasterised and then
output as images.
"""
def __init__(self, figure, width, height, dpi, vector_renderer,
raster_renderer_class=None,
bbox_inches_restore=None):
"""
figure: The figure instance.
width: The width of the canvas in logical units
height: The height of the canvas in logical units
dpi: The dpi of the canvas
vector_renderer: An instance of a subclass of RendererBase
that will be used for the vector drawing.
raster_renderer_class: The renderer class to use for the
raster drawing. If not provided, this will use the Agg
backend (which is currently the only viable option anyway.)
"""
if raster_renderer_class is None:
raster_renderer_class = RendererAgg
self._raster_renderer_class = raster_renderer_class
self._width = width
self._height = height
self.dpi = dpi
assert not vector_renderer.option_image_nocomposite()
self._vector_renderer = vector_renderer
self._raster_renderer = None
self._rasterizing = 0
# A renference to the figure is needed as we need to change
# the figure dpi before and after the rasterization. Although
# this looks ugly, I couldn't find a better solution. -JJL
self.figure=figure
self._bbox_inches_restore = bbox_inches_restore
self._set_current_renderer(vector_renderer)
_methods = """
close_group draw_image draw_markers draw_path
draw_path_collection draw_quad_mesh draw_tex draw_text
finalize flipy get_canvas_width_height get_image_magnification
get_texmanager get_text_width_height_descent new_gc open_group
option_image_nocomposite points_to_pixels strip_math
start_filter stop_filter draw_gouraud_triangle
draw_gouraud_triangles option_scale_image
""".split()
def _set_current_renderer(self, renderer):
self._renderer = renderer
for method in self._methods:
if hasattr(renderer, method):
setattr(self, method, getattr(renderer, method))
renderer.start_rasterizing = self.start_rasterizing
renderer.stop_rasterizing = self.stop_rasterizing
def start_rasterizing(self):
"""
Enter "raster" mode. All subsequent drawing commands (until
stop_rasterizing is called) will be drawn with the raster
backend.
If start_rasterizing is called multiple times before
stop_rasterizing is called, this method has no effect.
"""
# change the dpi of the figure temporarily.
self.figure.set_dpi(self.dpi)
if self._bbox_inches_restore: # when tight bbox is used
r = process_figure_for_rasterizing(self.figure,
self._bbox_inches_restore,
mode="png")
self._bbox_inches_restore = r
if self._rasterizing == 0:
self._raster_renderer = self._raster_renderer_class(
self._width*self.dpi, self._height*self.dpi, self.dpi)
self._set_current_renderer(self._raster_renderer)
self._rasterizing += 1
def stop_rasterizing(self):
"""
Exit "raster" mode. All of the drawing that was done since
the last start_rasterizing command will be copied to the
vector backend by calling draw_image.
If stop_rasterizing is called multiple times before
start_rasterizing is called, this method has no effect.
"""
self._rasterizing -= 1
if self._rasterizing == 0:
self._set_current_renderer(self._vector_renderer)
width, height = self._width * self.dpi, self._height * self.dpi
buffer, bounds = self._raster_renderer.tostring_rgba_minimized()
l, b, w, h = bounds
if w > 0 and h > 0:
image = frombuffer(buffer, w, h, True)
image.is_grayscale = False
image.flipud_out()
gc = self._renderer.new_gc()
self._renderer.draw_image(
gc,
float(l)/self.dpi*72.,
(float(height) - b - h)/self.dpi*72.,
image)
self._raster_renderer = None
self._rasterizing = False
# restore the figure dpi.
self.figure.set_dpi(72)
if self._bbox_inches_restore: # when tight bbox is used
r = process_figure_for_rasterizing(self.figure,
self._bbox_inches_restore,
mode="pdf")
self._bbox_inches_restore = r