backend_agg.py

"""
An agg http://antigrain.com/ 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

TODO:

  * integrate screen dpi w/ ppi and text

"""
try:
    import threading
except ImportError:
    import dummy_threading as threading
try:
    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'


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']]


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

    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

    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 = path.codes
                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)")

    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)

    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)

    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

    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)

    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

    def points_to_pixels(self, points):
        # docstring inherited
        return points * self.dpi / 72

    def buffer_rgba(self):
        return memoryview(self._renderer)

    def tostring_argb(self):
        return np.asarray(self._renderer).take([3, 0, 1, 2], axis=2).tobytes()

    def tostring_rgb(self):
        return np.asarray(self._renderer).take([0, 1, 2], axis=2).tobytes()

    def clear(self):
        self._renderer.clear()

    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

    def option_scale_image(self):
        # docstring inherited
        return False

    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)

    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()

    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)


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

    """

    def copy_from_bbox(self, bbox):
        renderer = self.get_renderer()
        return renderer.copy_from_bbox(bbox)

    def restore_region(self, region, bbox=None, xy=None):
        renderer = self.get_renderer()
        return renderer.restore_region(region, bbox, xy)

    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()

    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

    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()

    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()

    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()

    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

    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: \
                https://www.w3.org/TR/2003/REC-PNG-20031110/#11keywords

        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 `PIL.Image.save`.

            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__}, http://matplotlib.org/",
        }

        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})

    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).

        @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
                `PIL.Image.save` 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 = Image.new('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 background.save(
                filename_or_obj, format='jpeg', **pil_kwargs)

        print_jpeg = print_jpg

        @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