Source code for matplotlib.backends.backend_agg

An agg backend

Features that are implemented

 * capstyles and join styles
 * dashes
 * linewidth
 * lines, rectangles, ellipses
 * clipping to a rectangle
 * output to RGBA and PNG, optionally JPEG and TIFF
 * alpha blending
 * DPI scaling properly - everything scales properly (dashes, linewidths, etc)
 * draw polygon
 * freetype2 w/ ft2font


  * integrate screen dpi w/ ppi and text

    import threading
except ImportError:
    import dummy_threading as threading
    from contextlib import nullcontext
except ImportError:
    from contextlib import ExitStack as nullcontext  # Py 3.6.
from math import radians, cos, sin

import numpy as np

from matplotlib import cbook, rcParams, __version__
from matplotlib.backend_bases import (
    _Backend, FigureCanvasBase, FigureManagerBase, RendererBase)
from matplotlib.font_manager import findfont, get_font
from matplotlib.ft2font import (LOAD_FORCE_AUTOHINT, LOAD_NO_HINTING,
                                LOAD_DEFAULT, LOAD_NO_AUTOHINT)
from matplotlib.mathtext import MathTextParser
from matplotlib.path import Path
from matplotlib.transforms import Bbox, BboxBase
from matplotlib import colors as mcolors

from matplotlib.backends._backend_agg import RendererAgg as _RendererAgg

from matplotlib.backend_bases import _has_pil

if _has_pil:
    from PIL import Image

backend_version = 'v2.2'

[docs]def get_hinting_flag(): mapping = { True: LOAD_FORCE_AUTOHINT, False: LOAD_NO_HINTING, 'either': LOAD_DEFAULT, 'native': LOAD_NO_AUTOHINT, 'auto': LOAD_FORCE_AUTOHINT, 'none': LOAD_NO_HINTING } return mapping[rcParams['text.hinting']]
[docs]class RendererAgg(RendererBase): """ The renderer handles all the drawing primitives using a graphics context instance that controls the colors/styles """ # we want to cache the fonts at the class level so that when # multiple figures are created we can reuse them. This helps with # a bug on windows where the creation of too many figures leads to # too many open file handles. However, storing them at the class # level is not thread safe. The solution here is to let the # FigureCanvas acquire a lock on the fontd at the start of the # draw, and release it when it is done. This allows multiple # renderers to share the cached fonts, but only one figure can # draw at time and so the font cache is used by only one # renderer at a time. lock = threading.RLock() def __init__(self, width, height, dpi): RendererBase.__init__(self) self.dpi = dpi self.width = width self.height = height self._renderer = _RendererAgg(int(width), int(height), dpi) self._filter_renderers = [] self._update_methods() self.mathtext_parser = MathTextParser('Agg') self.bbox = Bbox.from_bounds(0, 0, self.width, self.height) def __getstate__(self): # We only want to preserve the init keywords of the Renderer. # Anything else can be re-created. return {'width': self.width, 'height': self.height, 'dpi': self.dpi} def __setstate__(self, state): self.__init__(state['width'], state['height'], state['dpi']) def _update_methods(self): self.draw_gouraud_triangle = self._renderer.draw_gouraud_triangle self.draw_gouraud_triangles = self._renderer.draw_gouraud_triangles self.draw_image = self._renderer.draw_image self.draw_markers = self._renderer.draw_markers self.draw_path_collection = self._renderer.draw_path_collection self.draw_quad_mesh = self._renderer.draw_quad_mesh self.copy_from_bbox = self._renderer.copy_from_bbox self.get_content_extents = self._renderer.get_content_extents
[docs] def tostring_rgba_minimized(self): extents = self.get_content_extents() bbox = [[extents[0], self.height - (extents[1] + extents[3])], [extents[0] + extents[2], self.height - extents[1]]] region = self.copy_from_bbox(bbox) return np.array(region), extents
[docs] def draw_path(self, gc, path, transform, rgbFace=None): # docstring inherited nmax = rcParams['agg.path.chunksize'] # here at least for testing npts = path.vertices.shape[0] if (nmax > 100 and npts > nmax and path.should_simplify and rgbFace is None and gc.get_hatch() is None): nch = np.ceil(npts / nmax) chsize = int(np.ceil(npts / nch)) i0 = np.arange(0, npts, chsize) i1 = np.zeros_like(i0) i1[:-1] = i0[1:] - 1 i1[-1] = npts for ii0, ii1 in zip(i0, i1): v = path.vertices[ii0:ii1, :] c = if c is not None: c = c[ii0:ii1] c[0] = Path.MOVETO # move to end of last chunk p = Path(v, c) try: self._renderer.draw_path(gc, p, transform, rgbFace) except OverflowError: raise OverflowError("Exceeded cell block limit (set " "'agg.path.chunksize' rcparam)") else: try: self._renderer.draw_path(gc, path, transform, rgbFace) except OverflowError: raise OverflowError("Exceeded cell block limit (set " "'agg.path.chunksize' rcparam)")
[docs] def draw_mathtext(self, gc, x, y, s, prop, angle): """ Draw the math text using matplotlib.mathtext """ ox, oy, width, height, descent, font_image, used_characters = \ self.mathtext_parser.parse(s, self.dpi, prop) xd = descent * sin(radians(angle)) yd = descent * cos(radians(angle)) x = round(x + ox + xd) y = round(y - oy + yd) self._renderer.draw_text_image(font_image, x, y + 1, angle, gc)
[docs] def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None): # docstring inherited if ismath: return self.draw_mathtext(gc, x, y, s, prop, angle) flags = get_hinting_flag() font = self._get_agg_font(prop) if font is None: return None # We pass '0' for angle here, since it will be rotated (in raster # space) in the following call to draw_text_image). font.set_text(s, 0, flags=flags) font.draw_glyphs_to_bitmap(antialiased=rcParams['text.antialiased']) d = font.get_descent() / 64.0 # The descent needs to be adjusted for the angle. xo, yo = font.get_bitmap_offset() xo /= 64.0 yo /= 64.0 xd = d * sin(radians(angle)) yd = d * cos(radians(angle)) x = round(x + xo + xd) y = round(y + yo + yd) self._renderer.draw_text_image(font, x, y + 1, angle, gc)
[docs] def get_text_width_height_descent(self, s, prop, ismath): # docstring inherited if ismath in ["TeX", "TeX!"]: # todo: handle props texmanager = self.get_texmanager() fontsize = prop.get_size_in_points() w, h, d = texmanager.get_text_width_height_descent( s, fontsize, renderer=self) return w, h, d if ismath: ox, oy, width, height, descent, fonts, used_characters = \ self.mathtext_parser.parse(s, self.dpi, prop) return width, height, descent flags = get_hinting_flag() font = self._get_agg_font(prop) font.set_text(s, 0.0, flags=flags) w, h = font.get_width_height() # width and height of unrotated string d = font.get_descent() w /= 64.0 # convert from subpixels h /= 64.0 d /= 64.0 return w, h, d
[docs] def draw_tex(self, gc, x, y, s, prop, angle, ismath='TeX!', mtext=None): # docstring inherited # todo, handle props, angle, origins size = prop.get_size_in_points() texmanager = self.get_texmanager() Z = texmanager.get_grey(s, size, self.dpi) Z = np.array(Z * 255.0, np.uint8) w, h, d = self.get_text_width_height_descent(s, prop, ismath) xd = d * sin(radians(angle)) yd = d * cos(radians(angle)) x = round(x + xd) y = round(y + yd) self._renderer.draw_text_image(Z, x, y, angle, gc)
[docs] def get_canvas_width_height(self): # docstring inherited return self.width, self.height
def _get_agg_font(self, prop): """ Get the font for text instance t, caching for efficiency """ fname = findfont(prop) font = get_font(fname) font.clear() size = prop.get_size_in_points() font.set_size(size, self.dpi) return font
[docs] def points_to_pixels(self, points): # docstring inherited return points * self.dpi / 72
[docs] def buffer_rgba(self): return memoryview(self._renderer)
[docs] def tostring_argb(self): return np.asarray(self._renderer).take([3, 0, 1, 2], axis=2).tobytes()
[docs] def tostring_rgb(self): return np.asarray(self._renderer).take([0, 1, 2], axis=2).tobytes()
[docs] def clear(self): self._renderer.clear()
[docs] def option_image_nocomposite(self): # docstring inherited # It is generally faster to composite each image directly to # the Figure, and there's no file size benefit to compositing # with the Agg backend return True
[docs] def option_scale_image(self): # docstring inherited return False
[docs] def restore_region(self, region, bbox=None, xy=None): """ Restore the saved region. If bbox (instance of BboxBase, or its extents) is given, only the region specified by the bbox will be restored. *xy* (a pair of floats) optionally specifies the new position (the LLC of the original region, not the LLC of the bbox) where the region will be restored. >>> region = renderer.copy_from_bbox() >>> x1, y1, x2, y2 = region.get_extents() >>> renderer.restore_region(region, bbox=(x1+dx, y1, x2, y2), ... xy=(x1-dx, y1)) """ if bbox is not None or xy is not None: if bbox is None: x1, y1, x2, y2 = region.get_extents() elif isinstance(bbox, BboxBase): x1, y1, x2, y2 = bbox.extents else: x1, y1, x2, y2 = bbox if xy is None: ox, oy = x1, y1 else: ox, oy = xy # The incoming data is float, but the _renderer type-checking wants # to see integers. self._renderer.restore_region(region, int(x1), int(y1), int(x2), int(y2), int(ox), int(oy)) else: self._renderer.restore_region(region)
[docs] def start_filter(self): """ Start filtering. It simply create a new canvas (the old one is saved). """ self._filter_renderers.append(self._renderer) self._renderer = _RendererAgg(int(self.width), int(self.height), self.dpi) self._update_methods()
[docs] def stop_filter(self, post_processing): """ Save the plot in the current canvas as a image and apply the *post_processing* function. def post_processing(image, dpi): # ny, nx, depth = image.shape # image (numpy array) has RGBA channels and has a depth of 4. ... # create a new_image (numpy array of 4 channels, size can be # different). The resulting image may have offsets from # lower-left corner of the original image return new_image, offset_x, offset_y The saved renderer is restored and the returned image from post_processing is plotted (using draw_image) on it. """ width, height = int(self.width), int(self.height) buffer, (l, b, w, h) = self.tostring_rgba_minimized() self._renderer = self._filter_renderers.pop() self._update_methods() if w > 0 and h > 0: img = np.frombuffer(buffer, np.uint8) img, ox, oy = post_processing(img.reshape((h, w, 4)) / 255., self.dpi) gc = self.new_gc() if img.dtype.kind == 'f': img = np.asarray(img * 255., np.uint8) img = img[::-1] self._renderer.draw_image(gc, l + ox, height - b - h + oy, img)
[docs]class FigureCanvasAgg(FigureCanvasBase): """ The canvas the figure renders into. Calls the draw and print fig methods, creates the renderers, etc... Attributes ---------- figure : `matplotlib.figure.Figure` A high-level Figure instance """
[docs] def copy_from_bbox(self, bbox): renderer = self.get_renderer() return renderer.copy_from_bbox(bbox)
[docs] def restore_region(self, region, bbox=None, xy=None): renderer = self.get_renderer() return renderer.restore_region(region, bbox, xy)
[docs] def draw(self): """ Draw the figure using the renderer. """ self.renderer = self.get_renderer(cleared=True) # Acquire a lock on the shared font cache. with RendererAgg.lock, \ (self.toolbar._wait_cursor_for_draw_cm() if self.toolbar else nullcontext()): self.figure.draw(self.renderer) # A GUI class may be need to update a window using this draw, so # don't forget to call the superclass. super().draw()
[docs] def get_renderer(self, cleared=False): l, b, w, h = self.figure.bbox.bounds key = w, h, self.figure.dpi reuse_renderer = (hasattr(self, "renderer") and getattr(self, "_lastKey", None) == key) if not reuse_renderer: self.renderer = RendererAgg(w, h, self.figure.dpi) self._lastKey = key elif cleared: self.renderer.clear() return self.renderer
[docs] def tostring_rgb(self): """Get the image as an RGB byte string. `draw` must be called at least once before this function will work and to update the renderer for any subsequent changes to the Figure. Returns ------- bytes """ return self.renderer.tostring_rgb()
[docs] def tostring_argb(self): """Get the image as an ARGB byte string. `draw` must be called at least once before this function will work and to update the renderer for any subsequent changes to the Figure. Returns ------- bytes """ return self.renderer.tostring_argb()
[docs] def buffer_rgba(self): """Get the image as a memoryview to the renderer's buffer. `draw` must be called at least once before this function will work and to update the renderer for any subsequent changes to the Figure. Returns ------- memoryview """ return self.renderer.buffer_rgba()
[docs] def print_raw(self, filename_or_obj, *args, **kwargs): FigureCanvasAgg.draw(self) renderer = self.get_renderer() with cbook.open_file_cm(filename_or_obj, "wb") as fh: fh.write(renderer.buffer_rgba())
print_rgba = print_raw
[docs] def print_png(self, filename_or_obj, *args, metadata=None, pil_kwargs=None, **kwargs): """ Write the figure to a PNG file. Parameters ---------- filename_or_obj : str or PathLike or file-like object The file to write to. metadata : dict, optional Metadata in the PNG file as key-value pairs of bytes or latin-1 encodable strings. According to the PNG specification, keys must be shorter than 79 chars. The `PNG specification`_ defines some common keywords that may be used as appropriate: - Title: Short (one line) title or caption for image. - Author: Name of image's creator. - Description: Description of image (possibly long). - Copyright: Copyright notice. - Creation Time: Time of original image creation (usually RFC 1123 format). - Software: Software used to create the image. - Disclaimer: Legal disclaimer. - Warning: Warning of nature of content. - Source: Device used to create the image. - Comment: Miscellaneous comment; conversion from other image format. Other keywords may be invented for other purposes. If 'Software' is not given, an autogenerated value for matplotlib will be used. For more details see the `PNG specification`_. .. _PNG specification: \ pil_kwargs : dict, optional If set to a non-None value, use Pillow to save the figure instead of Matplotlib's builtin PNG support, and pass these keyword arguments to ``. If the 'pnginfo' key is present, it completely overrides *metadata*, including the default 'Software' key. """ from matplotlib import _png if metadata is None: metadata = {} default_metadata = { "Software": f"matplotlib version{__version__},", } FigureCanvasAgg.draw(self) if pil_kwargs is not None: from PIL import Image from PIL.PngImagePlugin import PngInfo # Only use the metadata kwarg if pnginfo is not set, because the # semantics of duplicate keys in pnginfo is unclear. if "pnginfo" in pil_kwargs: if metadata: cbook._warn_external("'metadata' is overridden by the " "'pnginfo' entry in 'pil_kwargs'.") else: pnginfo = PngInfo() for k, v in {**default_metadata, **metadata}.items(): pnginfo.add_text(k, v) pil_kwargs["pnginfo"] = pnginfo pil_kwargs.setdefault("dpi", (self.figure.dpi, self.figure.dpi)) (Image.fromarray(np.asarray(self.buffer_rgba())) .save(filename_or_obj, format="png", **pil_kwargs)) else: renderer = self.get_renderer() with cbook.open_file_cm(filename_or_obj, "wb") as fh: _png.write_png(renderer._renderer, fh, self.figure.dpi, metadata={**default_metadata, **metadata})
[docs] def print_to_buffer(self): FigureCanvasAgg.draw(self) renderer = self.get_renderer() return (bytes(renderer.buffer_rgba()), (int(renderer.width), int(renderer.height)))
if _has_pil: # Note that these methods should typically be called via savefig() and # print_figure(), and the latter ensures that `self.figure.dpi` already # matches the dpi kwarg (if any).
[docs] @cbook._delete_parameter("3.2", "dryrun") def print_jpg(self, filename_or_obj, *args, dryrun=False, pil_kwargs=None, **kwargs): """ Write the figure to a JPEG file. Parameters ---------- filename_or_obj : str or PathLike or file-like object The file to write to. Other Parameters ---------------- quality : int The image quality, on a scale from 1 (worst) to 100 (best). The default is :rc:`savefig.jpeg_quality`. Values above 95 should be avoided; 100 completely disables the JPEG quantization stage. optimize : bool If present, indicates that the encoder should make an extra pass over the image in order to select optimal encoder settings. progressive : bool If present, indicates that this image should be stored as a progressive JPEG file. pil_kwargs : dict, optional Additional keyword arguments that are passed to `` when saving the figure. These take precedence over *quality*, *optimize* and *progressive*. """ FigureCanvasAgg.draw(self) if dryrun: return # The image is pasted onto a white background image to handle # transparency. image = Image.fromarray(np.asarray(self.buffer_rgba())) background ='RGB', image.size, "white") background.paste(image, image) if pil_kwargs is None: pil_kwargs = {} for k in ["quality", "optimize", "progressive"]: if k in kwargs: pil_kwargs.setdefault(k, kwargs[k]) pil_kwargs.setdefault("quality", rcParams["savefig.jpeg_quality"]) pil_kwargs.setdefault("dpi", (self.figure.dpi, self.figure.dpi)) return filename_or_obj, format='jpeg', **pil_kwargs)
print_jpeg = print_jpg
[docs] @cbook._delete_parameter("3.2", "dryrun") def print_tif(self, filename_or_obj, *args, dryrun=False, pil_kwargs=None, **kwargs): FigureCanvasAgg.draw(self) if dryrun: return if pil_kwargs is None: pil_kwargs = {} pil_kwargs.setdefault("dpi", (self.figure.dpi, self.figure.dpi)) return (Image.fromarray(np.asarray(self.buffer_rgba())) .save(filename_or_obj, format='tiff', **pil_kwargs))
print_tiff = print_tif
@_Backend.export class _BackendAgg(_Backend): FigureCanvas = FigureCanvasAgg FigureManager = FigureManagerBase