Source code for matplotlib.backends.backend_mixed

import numpy as np

from matplotlib import cbook
from matplotlib.backends.backend_agg import RendererAgg
from matplotlib.tight_bbox import process_figure_for_rasterizing

[docs]class MixedModeRenderer: """ 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): """ Parameters ---------- figure : `matplotlib.figure.Figure` The figure instance. width : scalar The width of the canvas in logical units height : scalar The height of the canvas in logical units dpi : float The dpi of the canvas vector_renderer : `matplotlib.backend_bases.RendererBase` An instance of a subclass of `~matplotlib.backend_bases.RendererBase` that will be used for the vector drawing. raster_renderer_class : `matplotlib.backend_bases.RendererBase` 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 self._vector_renderer = vector_renderer self._raster_renderer = None # A reference 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._figdpi = figure.get_dpi() self._bbox_inches_restore = bbox_inches_restore self._renderer = vector_renderer def __getattr__(self, attr): # Proxy everything that hasn't been overridden to the base # renderer. Things that *are* overridden can call methods # on self._renderer directly, but must not cache/store # methods (because things like RendererAgg change their # methods on the fly in order to optimise proxying down # to the underlying C implementation). return getattr(self._renderer, attr)
[docs] def start_rasterizing(self): """ Enter "raster" mode. All subsequent drawing commands (until `stop_rasterizing` is called) will be drawn with the raster backend. """ # 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) self._bbox_inches_restore = r self._raster_renderer = self._raster_renderer_class( self._width*self.dpi, self._height*self.dpi, self.dpi) self._renderer = self._raster_renderer
[docs] def stop_rasterizing(self): """ Exit "raster" mode. All of the drawing that was done since the last `start_rasterizing` call will be copied to the vector backend by calling draw_image. """ self._renderer = self._vector_renderer height = self._height * self.dpi img = np.asarray(self._raster_renderer.buffer_rgba()) slice_y, slice_x = cbook._get_nonzero_slices(img[..., 3]) cropped_img = img[slice_y, slice_x] if cropped_img.size: gc = self._renderer.new_gc() # TODO: If the mixedmode resolution differs from the figure's # dpi, the image must be scaled (dpi->_figdpi). Not all # backends support this. self._renderer.draw_image( gc, slice_x.start * self._figdpi / self.dpi, (height - slice_y.stop) * self._figdpi / self.dpi, cropped_img[::-1]) self._raster_renderer = None # restore the figure dpi. self.figure.set_dpi(self._figdpi) if self._bbox_inches_restore: # when tight bbox is used r = process_figure_for_rasterizing(self.figure, self._bbox_inches_restore, self._figdpi) self._bbox_inches_restore = r