120 lines
4.6 KiB
Python
120 lines
4.6 KiB
Python
import numpy as np
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from matplotlib import cbook
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from matplotlib.backends.backend_agg import RendererAgg
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from matplotlib.tight_bbox import process_figure_for_rasterizing
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class MixedModeRenderer:
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"""
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A helper class to implement a renderer that switches between
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vector and raster drawing. An example may be a PDF writer, where
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most things are drawn with PDF vector commands, but some very
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complex objects, such as quad meshes, are rasterised and then
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output as images.
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"""
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def __init__(self, figure, width, height, dpi, vector_renderer,
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raster_renderer_class=None,
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bbox_inches_restore=None):
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"""
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Parameters
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----------
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figure : `matplotlib.figure.Figure`
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The figure instance.
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width : scalar
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The width of the canvas in logical units
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height : scalar
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The height of the canvas in logical units
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dpi : float
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The dpi of the canvas
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vector_renderer : `matplotlib.backend_bases.RendererBase`
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An instance of a subclass of
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`~matplotlib.backend_bases.RendererBase` that will be used for the
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vector drawing.
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raster_renderer_class : `matplotlib.backend_bases.RendererBase`
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The renderer class to use for the raster drawing. If not provided,
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this will use the Agg backend (which is currently the only viable
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option anyway.)
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"""
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if raster_renderer_class is None:
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raster_renderer_class = RendererAgg
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self._raster_renderer_class = raster_renderer_class
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self._width = width
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self._height = height
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self.dpi = dpi
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self._vector_renderer = vector_renderer
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self._raster_renderer = None
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# A reference to the figure is needed as we need to change
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# the figure dpi before and after the rasterization. Although
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# this looks ugly, I couldn't find a better solution. -JJL
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self.figure = figure
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self._figdpi = figure.get_dpi()
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self._bbox_inches_restore = bbox_inches_restore
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self._renderer = vector_renderer
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def __getattr__(self, attr):
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# Proxy everything that hasn't been overridden to the base
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# renderer. Things that *are* overridden can call methods
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# on self._renderer directly, but must not cache/store
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# methods (because things like RendererAgg change their
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# methods on the fly in order to optimise proxying down
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# to the underlying C implementation).
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return getattr(self._renderer, attr)
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def start_rasterizing(self):
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"""
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Enter "raster" mode. All subsequent drawing commands (until
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`stop_rasterizing` is called) will be drawn with the raster backend.
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"""
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# change the dpi of the figure temporarily.
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self.figure.set_dpi(self.dpi)
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if self._bbox_inches_restore: # when tight bbox is used
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r = process_figure_for_rasterizing(self.figure,
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self._bbox_inches_restore)
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self._bbox_inches_restore = r
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self._raster_renderer = self._raster_renderer_class(
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self._width*self.dpi, self._height*self.dpi, self.dpi)
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self._renderer = self._raster_renderer
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def stop_rasterizing(self):
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"""
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Exit "raster" mode. All of the drawing that was done since
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the last `start_rasterizing` call will be copied to the
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vector backend by calling draw_image.
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"""
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self._renderer = self._vector_renderer
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height = self._height * self.dpi
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img = np.asarray(self._raster_renderer.buffer_rgba())
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slice_y, slice_x = cbook._get_nonzero_slices(img[..., 3])
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cropped_img = img[slice_y, slice_x]
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if cropped_img.size:
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gc = self._renderer.new_gc()
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# TODO: If the mixedmode resolution differs from the figure's
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# dpi, the image must be scaled (dpi->_figdpi). Not all
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# backends support this.
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self._renderer.draw_image(
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gc,
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slice_x.start * self._figdpi / self.dpi,
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(height - slice_y.stop) * self._figdpi / self.dpi,
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cropped_img[::-1])
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self._raster_renderer = None
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# restore the figure dpi.
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self.figure.set_dpi(self._figdpi)
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if self._bbox_inches_restore: # when tight bbox is used
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r = process_figure_for_rasterizing(self.figure,
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self._bbox_inches_restore,
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self._figdpi)
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self._bbox_inches_restore = r
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