349 lines
12 KiB
Python
349 lines
12 KiB
Python
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import re
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from collections import namedtuple
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from copy import copy
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from xml.etree.ElementTree import ElementTree
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from .image import BadImageOperationError, Image, SvgImageFile
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class WillowSvgException(Exception):
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pass
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class InvalidSvgAttribute(WillowSvgException):
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pass
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class InvalidSvgSizeAttribute(WillowSvgException):
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pass
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class SvgViewBoxParseError(WillowSvgException):
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pass
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ViewBox = namedtuple("ViewBox", "min_x min_y width height")
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def view_box_to_attr_str(view_box):
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return f"{view_box.min_x} {view_box.min_y} {view_box.width} {view_box.height}"
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class ViewportToUserSpaceTransform:
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def __init__(self, scale_x, scale_y, translate_x, translate_y):
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self.scale_x = scale_x
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self.scale_y = scale_y
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self.translate_x = translate_x
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self.translate_y = translate_y
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def __repr__(self):
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return (
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f"{self.__class__.__name__}(scale_x={self.scale_x}, scale_y="
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f"{self.scale_y}, translate_x={self.translate_x}, "
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f"translate_y={self.translate_y})"
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)
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def __eq__(self, other):
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if not isinstance(other, self.__class__):
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return False
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return (
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self.scale_x == other.scale_x
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and self.scale_y == other.scale_y
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and self.translate_x == other.translate_x
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and self.translate_y == other.translate_y
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)
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def __call__(self, rect):
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left, top, right, bottom = rect
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return (
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(left + self.translate_x) / self.scale_x,
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(top + self.translate_y) / self.scale_y,
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(right + self.translate_x) / self.scale_x,
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(bottom + self.translate_y) / self.scale_y,
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)
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def get_viewport_to_user_space_transform(
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svg: "SvgImage",
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) -> ViewportToUserSpaceTransform:
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# cairosvg used as a reference
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view_box = svg.image.view_box
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preserve_aspect_ratio = svg.image.preserve_aspect_ratio.split()
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try:
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align, meet_or_slice = preserve_aspect_ratio
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except ValueError:
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align = preserve_aspect_ratio[0]
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meet_or_slice = None
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scale_x = svg.image.width / view_box.width
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scale_y = svg.image.height / view_box.height
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if align == "none":
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# if align is "none", the viewBox will be scaled non-uniformly,
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# so we keep and use both scale_x and scale_y
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x_position = "min"
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y_position = "min"
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else:
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x_position = align[1:4].lower()
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y_position = align[5:].lower()
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choose_coefficient = max if meet_or_slice == "slice" else min
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# all values of preserveAspectRatio's `align', other than
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# "none", force uniform scaling, so choose the appropriate
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# coefficient and use it for scaling both axes
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scale_x = scale_y = choose_coefficient(scale_x, scale_y)
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# initial offsets to account for non-zero viewBox min-x and min-y
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translate_x = view_box.min_x * scale_x
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translate_y = view_box.min_y * scale_y
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# adjust the offsets by the amount the viewBox has been translated
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# to fit into the viewport (if any)
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if x_position == "mid":
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translate_x -= (svg.image.width - view_box.width * scale_x) / 2
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elif x_position == "max":
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translate_x -= svg.image.width - view_box.width * scale_x
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if y_position == "mid":
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translate_y -= (svg.image.height - view_box.height * scale_y) / 2
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elif y_position == "max":
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translate_y -= svg.image.height - view_box.height * scale_y
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return ViewportToUserSpaceTransform(scale_x, scale_y, translate_x, translate_y)
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class SvgWrapper:
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# https://developer.mozilla.org/en-US/docs/Web/SVG/Content_type#length
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UNIT_RE = re.compile(r"(?:em|ex|px|in|cm|mm|pt|pc|%)$")
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# https://www.w3.org/TR/SVG11/types.html#DataTypeNumber
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# https://www.w3.org/TR/2013/WD-SVG2-20130409/types.html#DataTypeNumber
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# This will exclude some inputs that Python will accept (e.g. "1.e9", "1."),
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# but for integration with other tools, we should adhere to the spec
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NUMBER_PATTERN = r"([+-]?(?:\d*\.)?\d+(?:[Ee][+-]?\d+)?)"
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# https://www.w3.org/Graphics/SVG/1.1/coords.html#ViewBoxAttribute
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VIEW_BOX_RE = re.compile(
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rf"^{NUMBER_PATTERN}(?:,\s*|\s+){NUMBER_PATTERN}(?:,\s*|\s+)"
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rf"{NUMBER_PATTERN}(?:,\s*|\s+){NUMBER_PATTERN}$"
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)
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PRESERVE_ASPECT_RATIO_RE = re.compile(
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r"^none$|^x(Min|Mid|Max)Y(Min|Mid|Max)(\s+(meet|slice))?$",
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)
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# Borrowed from cairosvg
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COEFFICIENTS = {
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"mm": 1 / 25.4,
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"cm": 1 / 2.54,
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"in": 1,
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"pt": 1 / 72.0,
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"pc": 1 / 6.0,
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}
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def __init__(self, dom: ElementTree, dpi=96, font_size_px=16):
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self.dom = dom
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self.dpi = dpi
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self.font_size_px = font_size_px
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self.view_box = self._get_view_box()
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self.preserve_aspect_ratio = self._get_preserve_aspect_ratio()
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width, width_unit = self._get_width()
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height, height_unit = self._get_height()
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# If one attr is missing or relative, we fall back to the other. After
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# this either both will be valid, or neither will, which will be handled
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# below. Relative width/height are treated as being undefined - so fall
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# back first to the other attribute, then the viewBox, then the browser
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# fallback. This gives us some flexibility for real world use cases, where
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# SVGs may have a relative height, a relative width, or both
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if width is None:
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width = height
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width_unit = height_unit
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elif height is None:
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height = width
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height_unit = width_unit
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elif width_unit == "%":
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width = height
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width_unit = height_unit
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elif height_unit == "%":
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height = width
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height_unit = width_unit
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# If the root svg element has no width, height, or viewBox attributes,
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# emulate browser behaviour and set width and height to 300 and 150
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# respectively, and set the viewBox to match
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# (https://svgwg.org/specs/integration/#svg-css-sizing). This means we
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# can always crop and resize without needing to rasterise
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if width is None and height is None or width_unit == "%" and height_unit == "%":
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if self.view_box is not None:
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self.width = self.view_box.width
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self.height = self.view_box.height
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else:
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self.width = 300
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self.height = 150
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else:
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self.width = self._convert_to_px(width, width_unit)
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self.height = self._convert_to_px(height, height_unit)
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if self.view_box is None:
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self.view_box = ViewBox(0, 0, self.width, self.height)
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def __copy__(self):
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# copy() called on ElementTree.Element makes a shallow copy (child
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# elements are shared with the original) so is efficient enough - we
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# only need to copy the root SVG element, as that is the only element
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# we will mutate
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dom = ElementTree(copy(self.dom.getroot()))
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return self.__class__(dom, dpi=self.dpi, font_size_px=self.font_size_px)
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@classmethod
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def from_file(cls, f):
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return cls(SvgImageFile(f).dom)
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@property
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def root(self):
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return self.dom.getroot()
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def _get_preserve_aspect_ratio(self):
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value = self.root.get("preserveAspectRatio", "").strip()
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if value == "":
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return "xMidYMid meet"
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if not self.PRESERVE_ASPECT_RATIO_RE.match(value):
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raise InvalidSvgAttribute(
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f"Unable to parse preserveAspectRatio value '{value}'"
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)
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return value
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def _get_width(self):
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attr_value = self.root.get("width")
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if attr_value:
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return self._parse_size(attr_value)
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return None, None
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def _get_height(self):
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attr_value = self.root.get("height")
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if attr_value:
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return self._parse_size(attr_value)
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return None, None
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def _parse_size(self, raw_value):
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clean_value = raw_value.strip()
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match = self.UNIT_RE.search(clean_value)
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unit = clean_value[match.start() :] if match else None
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amount_raw = clean_value[: -len(unit)] if unit else clean_value
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try:
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amount = float(amount_raw)
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except ValueError as err:
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raise InvalidSvgSizeAttribute(
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f"Unable to parse value from '{raw_value}'"
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) from err
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if amount <= 0:
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raise InvalidSvgSizeAttribute(f"Negative or 0 sizes are invalid ({amount})")
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return amount, unit
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def _convert_to_px(self, size, unit):
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if unit in (None, "px"):
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return size
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elif unit == "em":
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return size * self.font_size_px
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elif unit == "ex":
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# This is not exactly correct, but it's the best we can do
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return size * self.font_size_px / 2
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else:
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return size * self.dpi * self.COEFFICIENTS[unit]
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def _get_view_box(self):
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attr_value = self.root.get("viewBox")
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if attr_value:
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return self._parse_view_box(attr_value)
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@classmethod
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def _parse_view_box(cls, raw_value):
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match = cls.VIEW_BOX_RE.match(raw_value.strip())
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if match is None:
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raise SvgViewBoxParseError(f"Unable to parse viewBox value '{raw_value}'")
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return ViewBox(*map(float, match.groups()))
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def set_root_attr(self, attr, value):
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self.root.set(attr, str(value))
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def set_width(self, width):
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self.set_root_attr("width", width)
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self.width = width
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def set_height(self, height):
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self.set_root_attr("height", height)
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self.height = height
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def set_view_box(self, view_box):
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self.set_root_attr("viewBox", view_box_to_attr_str(view_box))
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self.view_box = view_box
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def write(self, f):
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self.dom.write(f, encoding="utf-8")
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class SvgImage(Image):
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def __init__(self, image):
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self.image: SvgWrapper = image
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@Image.operation
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def crop(self, rect, get_transformer=get_viewport_to_user_space_transform):
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left, top, right, bottom = rect
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if left >= right or top >= bottom:
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raise BadImageOperationError(f"Invalid crop dimensions: {rect}")
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viewport_width = right - left
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viewport_height = bottom - top
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transformed_rect = get_transformer(self)(rect)
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left, top, right, bottom = transformed_rect
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svg_wrapper = copy(self.image)
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view_box_width = right - left
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view_box_height = bottom - top
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svg_wrapper.set_view_box(ViewBox(left, top, view_box_width, view_box_height))
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svg_wrapper.set_width(viewport_width)
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svg_wrapper.set_height(viewport_height)
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return self.__class__(image=svg_wrapper)
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@Image.operation
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def resize(self, size):
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new_width, new_height = size
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if new_width < 1 or new_height < 1:
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raise BadImageOperationError(f"Invalid resize dimensions: {size}")
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svg_wrapper = copy(self.image)
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svg_wrapper.set_width(new_width)
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svg_wrapper.set_height(new_height)
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return self.__class__(image=svg_wrapper)
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@Image.operation
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def get_size(self):
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return (self.image.width, self.image.height)
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@Image.operation
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def auto_orient(self):
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return self
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@Image.operation
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def has_animation(self):
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return False
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@Image.operation
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def get_frame_count(self):
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return 1
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def write(self, f):
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self.image.write(f)
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f.seek(0)
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@Image.operation
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def save_as_svg(self, f):
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self.write(f)
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return SvgImageFile(f, dom=self.image.dom)
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@classmethod
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@Image.converter_from(SvgImageFile)
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def open(cls, svg_image_file):
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return cls(image=SvgWrapper(svg_image_file.dom))
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