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- import numpy as np
- from matplotlib import cbook
- from .backend_agg import RendererAgg
- from matplotlib._tight_bbox import process_figure_for_rasterizing
- 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.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)
- 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.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
- 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.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
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