529 lines
20 KiB
Python
529 lines
20 KiB
Python
"""
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weasyprint.images
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-----------------
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Fetch and decode images in various formats.
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:copyright: Copyright 2011-2019 Simon Sapin and contributors, see AUTHORS.
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:license: BSD, see LICENSE for details.
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"""
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import math
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from io import BytesIO
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from xml.etree import ElementTree
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import cairocffi
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import cairosvg.parser
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import cairosvg.surface
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from .layout.percentages import percentage
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from .logger import LOGGER
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from .urls import URLFetchingError, fetch
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try:
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from cairocffi import pixbuf
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except OSError:
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pixbuf = None
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assert cairosvg.surface.cairo is cairocffi, (
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'CairoSVG is using pycairo instead of cairocffi. '
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'Make sure it is not imported before WeasyPrint.')
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# Map values of the image-rendering property to cairo FILTER values:
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# Values are normalized to lower case.
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IMAGE_RENDERING_TO_FILTER = {
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'auto': cairocffi.FILTER_BILINEAR,
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'crisp-edges': cairocffi.FILTER_BEST,
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'pixelated': cairocffi.FILTER_NEAREST,
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}
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class ImageLoadingError(ValueError):
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"""An error occured when loading an image.
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The image data is probably corrupted or in an invalid format.
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"""
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@classmethod
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def from_exception(cls, exception):
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name = type(exception).__name__
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value = str(exception)
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return cls('%s: %s' % (name, value) if value else name)
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class RasterImage(object):
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def __init__(self, image_surface):
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self.image_surface = image_surface
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self._intrinsic_width = image_surface.get_width()
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self._intrinsic_height = image_surface.get_height()
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self.intrinsic_ratio = (
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self._intrinsic_width / self._intrinsic_height
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if self._intrinsic_height != 0 else float('inf'))
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def get_intrinsic_size(self, image_resolution, _font_size):
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# Raster images are affected by the 'image-resolution' property.
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return (self._intrinsic_width / image_resolution,
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self._intrinsic_height / image_resolution)
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def draw(self, context, concrete_width, concrete_height, image_rendering):
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has_size = (
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concrete_width > 0
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and concrete_height > 0
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and self._intrinsic_width > 0
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and self._intrinsic_height > 0
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)
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if not has_size:
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return
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# Use the real intrinsic size here,
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# not affected by 'image-resolution'.
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context.scale(concrete_width / self._intrinsic_width,
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concrete_height / self._intrinsic_height)
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context.set_source_surface(self.image_surface)
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context.get_source().set_filter(
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IMAGE_RENDERING_TO_FILTER[image_rendering])
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context.paint()
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class ScaledSVGSurface(cairosvg.surface.SVGSurface):
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"""
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Have the cairo Surface object have intrinsic dimension
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in pixels instead of points.
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"""
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@property
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def device_units_per_user_units(self):
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scale = super().device_units_per_user_units
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return scale / 0.75
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class FakeSurface(object):
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"""Fake CairoSVG surface used to get SVG attributes."""
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context_height = 0
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context_width = 0
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font_size = 12
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dpi = 96
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class SVGImage(object):
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def __init__(self, svg_data, base_url, url_fetcher):
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# Don’t pass data URIs to CairoSVG.
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# They are useless for relative URIs anyway.
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self._base_url = (
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base_url if not base_url.lower().startswith('data:') else None)
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self._svg_data = svg_data
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self._url_fetcher = url_fetcher
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try:
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self._tree = ElementTree.fromstring(self._svg_data)
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except Exception as e:
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raise ImageLoadingError.from_exception(e)
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def _cairosvg_url_fetcher(self, src, mimetype):
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data = self._url_fetcher(src)
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if 'string' in data:
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return data['string']
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return data['file_obj'].read()
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def get_intrinsic_size(self, _image_resolution, font_size):
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# Vector images may be affected by the font size.
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fake_surface = FakeSurface()
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fake_surface.font_size = font_size
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# Percentages don't provide an intrinsic size, we transform percentages
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# into 0 using a (0, 0) context size:
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# http://www.w3.org/TR/SVG/coords.html#IntrinsicSizing
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self._width = cairosvg.surface.size(
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fake_surface, self._tree.get('width'))
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self._height = cairosvg.surface.size(
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fake_surface, self._tree.get('height'))
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_, _, viewbox = cairosvg.surface.node_format(fake_surface, self._tree)
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self._intrinsic_width = self._width or None
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self._intrinsic_height = self._height or None
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self.intrinsic_ratio = None
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if viewbox:
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if self._width and self._height:
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self.intrinsic_ratio = self._width / self._height
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else:
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if viewbox[2] and viewbox[3]:
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self.intrinsic_ratio = viewbox[2] / viewbox[3]
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if self._width:
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self._intrinsic_height = (
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self._width / self.intrinsic_ratio)
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elif self._height:
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self._intrinsic_width = (
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self._height * self.intrinsic_ratio)
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elif self._width and self._height:
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self.intrinsic_ratio = self._width / self._height
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return self._intrinsic_width, self._intrinsic_height
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def draw(self, context, concrete_width, concrete_height, _image_rendering):
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try:
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svg = ScaledSVGSurface(
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cairosvg.parser.Tree(
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bytestring=self._svg_data, url=self._base_url,
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url_fetcher=self._cairosvg_url_fetcher),
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output=None, dpi=96, output_width=concrete_width,
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output_height=concrete_height)
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if svg.width and svg.height:
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context.scale(
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concrete_width / svg.width, concrete_height / svg.height)
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context.set_source_surface(svg.cairo)
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context.paint()
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except Exception as e:
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LOGGER.error(
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'Failed to draw an SVG image at %s : %s', self._base_url, e)
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def get_image_from_uri(cache, url_fetcher, url, forced_mime_type=None):
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"""Get a cairo Pattern from an image URI."""
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missing = object()
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image = cache.get(url, missing)
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if image is not missing:
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return image
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try:
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with fetch(url_fetcher, url) as result:
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if 'string' in result:
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string = result['string']
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else:
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string = result['file_obj'].read()
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mime_type = forced_mime_type or result['mime_type']
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if mime_type == 'image/svg+xml':
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# No fallback for XML-based mimetypes as defined by MIME
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# Sniffing Standard, see https://mimesniff.spec.whatwg.org/
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image = SVGImage(string, url, url_fetcher)
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else:
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# Try to rely on given mimetype
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try:
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if mime_type == 'image/png':
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try:
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surface = cairocffi.ImageSurface.create_from_png(
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BytesIO(string))
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except Exception as exception:
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raise ImageLoadingError.from_exception(exception)
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else:
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image = RasterImage(surface)
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else:
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image = None
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except ImageLoadingError:
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image = None
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# Relying on mimetype didn't work, give the image to GDK-Pixbuf
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if not image:
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if pixbuf is None:
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raise ImageLoadingError(
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'Could not load GDK-Pixbuf. PNG and SVG are '
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'the only image formats available.')
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try:
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image = SVGImage(string, url, url_fetcher)
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except BaseException:
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try:
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surface, format_name = (
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pixbuf.decode_to_image_surface(string))
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except pixbuf.ImageLoadingError as exception:
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raise ImageLoadingError(str(exception))
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if format_name == 'jpeg':
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surface.set_mime_data('image/jpeg', string)
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image = RasterImage(surface)
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except (URLFetchingError, ImageLoadingError) as exc:
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LOGGER.error('Failed to load image at "%s" (%s)', url, exc)
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image = None
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cache[url] = image
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return image
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def process_color_stops(gradient_line_size, positions):
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"""
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Gradient line size: distance between the starting point and ending point.
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Positions: list of None, or Dimension in px or %.
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0 is the starting point, 1 the ending point.
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http://dev.w3.org/csswg/css-images-3/#color-stop-syntax
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Return processed color stops, as a list of floats in px.
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"""
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positions = [
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percentage(position, gradient_line_size) for position in positions]
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# First and last default to 100%
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if positions[0] is None:
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positions[0] = 0
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if positions[-1] is None:
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positions[-1] = gradient_line_size
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# Make sure positions are increasing.
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previous_pos = positions[0]
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for i, position in enumerate(positions):
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if position is not None:
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if position < previous_pos:
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positions[i] = previous_pos
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else:
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previous_pos = position
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# Assign missing values
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previous_i = -1
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for i, position in enumerate(positions):
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if position is not None:
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base = positions[previous_i]
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increment = (position - base) / (i - previous_i)
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for j in range(previous_i + 1, i):
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positions[j] = base + j * increment
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previous_i = i
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return positions
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def normalize_stop_postions(positions):
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"""Normalize to [0..1]."""
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first = positions[0]
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last = positions[-1]
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total_length = last - first
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if total_length != 0:
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positions = [(pos - first) / total_length for pos in positions]
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else:
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positions = [0 for _ in positions]
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return first, last, positions
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def gradient_average_color(colors, positions):
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"""
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http://dev.w3.org/csswg/css-images-3/#find-the-average-color-of-a-gradient
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"""
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nb_stops = len(positions)
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assert nb_stops > 1
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assert nb_stops == len(colors)
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total_length = positions[-1] - positions[0]
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if total_length == 0:
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positions = list(range(nb_stops))
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total_length = nb_stops - 1
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premul_r = [r * a for r, g, b, a in colors]
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premul_g = [g * a for r, g, b, a in colors]
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premul_b = [b * a for r, g, b, a in colors]
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alpha = [a for r, g, b, a in colors]
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result_r = result_g = result_b = result_a = 0
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total_weight = 2 * total_length
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for i, position in enumerate(positions[1:], 1):
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weight = (position - positions[i - 1]) / total_weight
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for j in (i - 1, i):
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result_r += premul_r[j] * weight
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result_g += premul_g[j] * weight
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result_b += premul_b[j] * weight
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result_a += alpha[j] * weight
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# Un-premultiply:
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return (result_r / result_a, result_g / result_a,
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result_b / result_a, result_a) if result_a != 0 else (0, 0, 0, 0)
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PATTERN_TYPES = dict(
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linear=cairocffi.LinearGradient,
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radial=cairocffi.RadialGradient,
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solid=cairocffi.SolidPattern)
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class Gradient(object):
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def __init__(self, color_stops, repeating):
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assert color_stops
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#: List of (r, g, b, a), list of Dimension
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self.colors = [color for color, position in color_stops]
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self.stop_positions = [position for color, position in color_stops]
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#: bool
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self.repeating = repeating
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def get_intrinsic_size(self, _image_resolution, _font_size):
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# Gradients are not affected by image resolution, parent or font size.
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return None, None
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intrinsic_ratio = None
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def draw(self, context, concrete_width, concrete_height, _image_rendering):
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scale_y, type_, init, stop_positions, stop_colors = self.layout(
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concrete_width, concrete_height, context.user_to_device_distance)
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context.scale(1, scale_y)
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pattern = PATTERN_TYPES[type_](*init)
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for position, color in zip(stop_positions, stop_colors):
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pattern.add_color_stop_rgba(position, *color)
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pattern.set_extend(cairocffi.EXTEND_REPEAT if self.repeating
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else cairocffi.EXTEND_PAD)
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context.set_source(pattern)
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context.paint()
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def layout(self, width, height, user_to_device_distance):
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"""width, height: Gradient box. Top-left is at coordinates (0, 0).
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user_to_device_distance: a (dx, dy) -> (ddx, ddy) function
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Returns (scale_y, type_, init, positions, colors).
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scale_y: float, used for ellipses radial gradients. 1 otherwise.
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positions: list of floats in [0..1].
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0 at the starting point, 1 at the ending point.
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colors: list of (r, g, b, a)
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type_ is either:
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'solid': init is (r, g, b, a). positions and colors are empty.
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'linear': init is (x0, y0, x1, y1)
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coordinates of the starting and ending points.
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'radial': init is (cx0, cy0, radius0, cx1, cy1, radius1)
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coordinates of the starting end ending circles
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"""
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raise NotImplementedError
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class LinearGradient(Gradient):
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def __init__(self, color_stops, direction, repeating):
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Gradient.__init__(self, color_stops, repeating)
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#: ('corner', keyword) or ('angle', radians)
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self.direction_type, self.direction = direction
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def layout(self, width, height, user_to_device_distance):
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if len(self.colors) == 1:
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return 1, 'solid', self.colors[0], [], []
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# (dx, dy) is the unit vector giving the direction of the gradient.
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# Positive dx: right, positive dy: down.
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if self.direction_type == 'corner':
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factor_x, factor_y = {
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'top_left': (-1, -1), 'top_right': (1, -1),
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'bottom_left': (-1, 1), 'bottom_right': (1, 1)}[self.direction]
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diagonal = math.hypot(width, height)
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# Note the direction swap: dx based on height, dy based on width
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# The gradient line is perpendicular to a diagonal.
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dx = factor_x * height / diagonal
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dy = factor_y * width / diagonal
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else:
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angle = self.direction # 0 upwards, then clockwise
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dx = math.sin(angle)
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dy = -math.cos(angle)
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# Distance between center and ending point,
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# ie. half of between the starting point and ending point:
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distance = abs(width * dx) + abs(height * dy)
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positions = process_color_stops(distance, self.stop_positions)
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first, last, positions = normalize_stop_postions(positions)
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device_per_user_units = math.hypot(*user_to_device_distance(dx, dy))
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if (last - first) * device_per_user_units < len(positions):
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if self.repeating:
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color = gradient_average_color(self.colors, positions)
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return 1, 'solid', color, [], []
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else:
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# 100 is an Arbitrary non-zero number of device units.
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offset = 100 / device_per_user_units
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if first != last:
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factor = (offset + last - first) / (last - first)
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positions = [pos / factor for pos in positions]
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last += offset
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start_x = (width - dx * distance) / 2
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start_y = (height - dy * distance) / 2
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points = (start_x + dx * first, start_y + dy * first,
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start_x + dx * last, start_y + dy * last)
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return 1, 'linear', points, positions, self.colors
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class RadialGradient(Gradient):
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def __init__(self, color_stops, shape, size, center, repeating):
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Gradient.__init__(self, color_stops, repeating)
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# Center of the ending shape. (origin_x, pos_x, origin_y, pos_y)
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self.center = center
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#: Type of ending shape: 'circle' or 'ellipse'
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self.shape = shape
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# size_type: 'keyword'
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# size: 'closest-corner', 'farthest-corner',
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# 'closest-side', or 'farthest-side'
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# size_type: 'explicit'
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# size: (radius_x, radius_y)
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self.size_type, self.size = size
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def layout(self, width, height, user_to_device_distance):
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if len(self.colors) == 1:
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return 1, 'solid', self.colors[0], [], []
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origin_x, center_x, origin_y, center_y = self.center
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center_x = percentage(center_x, width)
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center_y = percentage(center_y, height)
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if origin_x == 'right':
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center_x = width - center_x
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if origin_y == 'bottom':
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center_y = height - center_y
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size_x, size_y = self._resolve_size(width, height, center_x, center_y)
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# http://dev.w3.org/csswg/css-images-3/#degenerate-radials
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if size_x == size_y == 0:
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size_x = size_y = 1e-7
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elif size_x == 0:
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size_x = 1e-7
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size_y = 1e7
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elif size_y == 0:
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size_x = 1e7
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size_y = 1e-7
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scale_y = size_y / size_x
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colors = self.colors
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positions = process_color_stops(size_x, self.stop_positions)
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gradient_line_size = positions[-1] - positions[0]
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if self.repeating and any(
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gradient_line_size * unit < len(positions)
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for unit in (math.hypot(*user_to_device_distance(1, 0)),
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math.hypot(*user_to_device_distance(0, scale_y)))):
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color = gradient_average_color(colors, positions)
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return 1, 'solid', color, [], []
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if positions[0] < 0:
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# Cairo does not like negative radiuses,
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# shift into the positive realm.
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if self.repeating:
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offset = gradient_line_size * math.ceil(
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-positions[0] / gradient_line_size)
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positions = [p + offset for p in positions]
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else:
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for i, position in enumerate(positions):
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if position > 0:
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# `i` is the first positive stop.
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# Interpolate with the previous to get the color at 0.
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assert i > 0
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color = colors[i]
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neg_color = colors[i - 1]
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neg_position = positions[i - 1]
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assert neg_position < 0
|
||
intermediate_color = gradient_average_color(
|
||
[neg_color, neg_color, color, color],
|
||
[neg_position, 0, 0, position])
|
||
colors = [intermediate_color] + colors[i:]
|
||
positions = [0] + positions[i:]
|
||
break
|
||
else:
|
||
# All stops are negatives,
|
||
# everything is "padded" with the last color.
|
||
return 1, 'solid', self.colors[-1], [], []
|
||
|
||
first, last, positions = normalize_stop_postions(positions)
|
||
if last == first:
|
||
last += 100 # Arbitrary non-zero
|
||
|
||
circles = (center_x, center_y / scale_y, first,
|
||
center_x, center_y / scale_y, last)
|
||
return scale_y, 'radial', circles, positions, colors
|
||
|
||
def _resolve_size(self, width, height, center_x, center_y):
|
||
if self.size_type == 'explicit':
|
||
size_x, size_y = self.size
|
||
size_x = percentage(size_x, width)
|
||
size_y = percentage(size_y, height)
|
||
return size_x, size_y
|
||
left = abs(center_x)
|
||
right = abs(width - center_x)
|
||
top = abs(center_y)
|
||
bottom = abs(height - center_y)
|
||
pick = min if self.size.startswith('closest') else max
|
||
if self.size.endswith('side'):
|
||
if self.shape == 'circle':
|
||
size_xy = pick(left, right, top, bottom)
|
||
return size_xy, size_xy
|
||
# else: ellipse
|
||
return pick(left, right), pick(top, bottom)
|
||
# else: corner
|
||
if self.shape == 'circle':
|
||
size_xy = pick(math.hypot(left, top), math.hypot(left, bottom),
|
||
math.hypot(right, top), math.hypot(right, bottom))
|
||
return size_xy, size_xy
|
||
# else: ellipse
|
||
corner_x, corner_y = pick(
|
||
(left, top), (left, bottom), (right, top), (right, bottom),
|
||
key=lambda a: math.hypot(*a))
|
||
return corner_x * math.sqrt(2), corner_y * math.sqrt(2)
|