scale height to (ascender-descender), preserve aspect, center width

src/nanoemoji/color_glyph.py

@@ -37,52 +37,60 @@
 import ufoLib2
 
 
-def _scale_viewbox_to_emsquare(view_box: Rect, upem: int) -> Tuple[float, float]:
- # scale to font upem
- return (upem / view_box.w, upem / view_box.h)
-
-
-def _shift_origin_0_0(
- view_box: Rect, x_scale: float, y_scale: float
-) -> Tuple[float, float]:
- # shift so origin is 0,0
- return (-view_box.x * x_scale, -view_box.y * y_scale)
+def _scale_viewbox_to_font_metrics(
+ view_box: Rect, ascender: int, descender: int, width: int
+):
+ assert descender <= 0
+ # scale height to (ascender - descender)
+ scale = (ascender - descender) / view_box.h
+ # shift so width is centered
+ dx = (width - scale * view_box.w) / 2
+ return Affine2D.compose_ltr(
+ (
+ # first normalize viewbox origin
+ Affine2D(1, 0, 0, 1, -view_box.x, -view_box.y),
+ Affine2D(scale, 0, 0, scale, dx, 0),
+ )
+ )
 
 
-def map_viewbox_to_font_emsquare(
- view_box: Rect, upem: int, user_transform: Affine2D
+def map_viewbox_to_font_space(
+ view_box: Rect, ascender: int, descender: int, width: int, user_transform: Affine2D
 ) -> Affine2D:
- x_scale, y_scale = _scale_viewbox_to_emsquare(view_box, upem)
- # flip y axis
- y_scale = -y_scale
- # shift so things are in the right place
- dx, dy = _shift_origin_0_0(view_box, x_scale, y_scale)
- dy = dy + upem
- affine = Affine2D(x_scale, 0, 0, y_scale, dx, dy)
- return Affine2D.compose_ltr((affine, user_transform))
+ return Affine2D.compose_ltr(
+  [
+  _scale_viewbox_to_font_metrics(view_box, ascender, descender, width),
+  # flip y axis and shift so things are in the right place
+  Affine2D(1, 0, 0, -1, 0, ascender),
+  user_transform,
+  ]
+ )
 
 
 # https://docs.microsoft.com/en-us/typography/opentype/spec/svg#coordinate-systems-and-glyph-metrics
-def map_viewbox_to_otsvg_emsquare(
- view_box: Rect, upem: int, user_transform: Affine2D
+def map_viewbox_to_otsvg_space(
+ view_box: Rect, ascender: int, descender: int, width: int, user_transform: Affine2D
 ) -> Affine2D:
- x_scale, y_scale = _scale_viewbox_to_emsquare(view_box, upem)
- dx, dy = _shift_origin_0_0(view_box, x_scale, y_scale)
-
- # shift so things are in the right place
- dy = dy - upem
- affine = Affine2D(x_scale, 0, 0, y_scale, dx, dy)
- return Affine2D.compose_ltr((affine, user_transform))
+ return Affine2D.compose_ltr(
+ [
+ _scale_viewbox_to_font_metrics(view_box, ascender, descender, width),
+ # shift things in the [+x,-y] quadrant where OT-SVG expects them
+ Affine2D(1, 0, 0, 1, 0, -ascender),
+ user_transform,
+ ]
+ )
 
 
 def _get_gradient_transform(
- upem: int,
- user_transform: Affine2D,
+ config: FontConfig,
  grad_el: etree.Element,
  shape_bbox: Rect,
  view_box: Rect,
+ glyph_width: int,
 ) -> Affine2D:
- transform = map_viewbox_to_font_emsquare(view_box, upem, user_transform)
+ transform = map_viewbox_to_font_space(
+ view_box, config.ascender, config.descender, glyph_width, config.transform
+ )
 
  gradient_units = grad_el.attrib.get("gradientUnits", "objectBoundingBox")
  if gradient_units == "objectBoundingBox":
@@ -102,6 +110,7 @@ def _parse_linear_gradient(
  grad_el: etree.Element,
  shape_bbox: Rect,
  view_box: Rect,
+ glyph_width: int,
  shape_opacity: float = 1.0,
 ):
  gradient = SVGLinearGradient.from_element(grad_el, view_box)
@@ -113,7 +122,7 @@ def _parse_linear_gradient(
  p2 = p0 + (p1 - p0).perpendicular()
 
  transform = _get_gradient_transform(
- config.upem, config.transform, grad_el, shape_bbox, view_box
+ config, grad_el, shape_bbox, view_box, glyph_width
  )
 
  p0 = transform.map_point(p0)
@@ -131,6 +140,7 @@ def _parse_radial_gradient(
  grad_el: etree.Element,
  shape_bbox: Rect,
  view_box: Rect,
+ glyph_width: int,
  shape_opacity: float = 1.0,
 ):
  gradient = SVGRadialGradient.from_element(grad_el, view_box)
@@ -140,7 +150,9 @@ def _parse_radial_gradient(
  c1 = Point(gradient.cx, gradient.cy)
  r1 = gradient.r
 
- transform = map_viewbox_to_font_emsquare(view_box, config.upem, config.transform)
+ transform = map_viewbox_to_font_space(
+ view_box, config.ascender, config.descender, glyph_width, config.transform
+ )
 
  gradient_units = grad_el.attrib.get("gradientUnits", "objectBoundingBox")
  if gradient_units == "objectBoundingBox":
@@ -150,7 +162,7 @@ def _parse_radial_gradient(
 
  assert transform[1:3] == (0, 0), (
  f"{transform} contains unexpected skew/rotation:"
- " upem, view_box, shape_bbox are all rectangles"
+ " (ascender-descender), view_box, shape_bbox are all rectangles"
  )
 
  # if viewBox is not square or if gradientUnits="objectBoundingBox" and the bbox
@@ -237,7 +249,9 @@ def shape_cache_key(self):
  return (self.path, self.reuses)
 
 
-def _paint(debug_hint: str, config: FontConfig, picosvg: SVG, shape: SVGPath) -> Paint:
+def _paint(
+ debug_hint: str, config: FontConfig, picosvg: SVG, shape: SVGPath, glyph_width: int
+) -> Paint:
  if shape.fill.startswith("url("):
  el = picosvg.resolve_url(shape.fill, "*")
  try:
@@ -246,6 +260,7 @@ def _paint(debug_hint: str, config: FontConfig, picosvg: SVG, shape: SVGPath) ->
  el,
  shape.bounding_box(),
  picosvg.view_box(),
+ glyph_width,
  shape.opacity,
  )
  except ValueError as e:
@@ -257,12 +272,12 @@ def _paint(debug_hint: str, config: FontConfig, picosvg: SVG, shape: SVGPath) ->
 
 
 def _in_glyph_reuse_key(
- debug_hint: str, config: FontConfig, picosvg: SVG, shape: SVGPath
+ debug_hint: str, config: FontConfig, picosvg: SVG, shape: SVGPath, glyph_width: int
 ) -> Tuple[Paint, SVGPath]:
  """Within a glyph reuse shapes only when painted consistently.
  paint+normalized shape ensures this."""
  return (
- _paint(debug_hint, config, picosvg, shape),
+ _paint(debug_hint, config, picosvg, shape, glyph_width),
  normalize(shape, config.reuse_tolerance),
  )
 
@@ -271,18 +286,21 @@ def _painted_layers(
  debug_hint: str,
  config: FontConfig,
  picosvg: SVG,
+ glyph_width: int,
 ) -> Generator[PaintedLayer, None, None]:
  if config.reuse_tolerance < 0:
  # shape reuse disabled
  for path in picosvg.shapes():
- yield PaintedLayer(_paint(debug_hint, config, picosvg, path), path.d)
+ yield PaintedLayer(
+ _paint(debug_hint, config, picosvg, path, glyph_width), path.d
+ )
  return
 
  # Don't sort; we only want to find groups that are consecutive in the picosvg
  # to ensure we don't mess up layer order
  for (paint, normalized), paths in groupby(
  picosvg.shapes(),
- key=lambda s: _in_glyph_reuse_key(debug_hint, config, picosvg, s),
+ key=lambda s: _in_glyph_reuse_key(debug_hint, config, picosvg, s, glyph_width),
  ):
  paths = list(paths)
  transforms = ()
@@ -311,6 +329,13 @@ def _painted_layers(
  yield PaintedLayer(paint, path.d)
 
 
+def _color_glyph_advance_width(view_box: Rect, config: FontConfig) -> int:
+ # Scale advance width proportionally to viewbox aspect ratio.
+ # Use the default advance width if it's larger than the proportional one.
+ font_height = config.ascender - config.descender # descender <= 0
+ return max(config.width, round(font_height * view_box.w / view_box.h))
+
+
 class ColorGlyph(NamedTuple):
  ufo: ufoLib2.Font
  filename: str
@@ -333,7 +358,13 @@ def create(
  logging.debug(" ColorGlyph for %s (%s)", filename, codepoints)
  glyph_name = glyph.glyph_name(codepoints)
  base_glyph = ufo.newGlyph(glyph_name)
- base_glyph.width = font_config.width
+
+ # non-square aspect ratio == proportional width; square == monospace
+ view_box = svg.view_box()
+ if view_box is not None:
+ base_glyph.width = _color_glyph_advance_width(view_box, font_config)
+ else:
+ base_glyph.width = font_config.width
 
  # Setup direct access to the glyph if possible
  if len(codepoints) == 1:
@@ -347,6 +378,7 @@ def create(
  filename,
  font_config,
  svg,
+ base_glyph.width,
  )
  )
 
@@ -369,21 +401,22 @@ def _has_viewbox_for_transform(self) -> bool:
  )
  return view_box is not None
 
- def transform_for_font_space(self):
- """Creates a Transform to map SVG coords to font coords"""
+ def _transform(self, map_fn):
  if not self._has_viewbox_for_transform():
  return Affine2D.identity()
- return map_viewbox_to_font_emsquare(
- self.svg.view_box(), self.ufo.info.unitsPerEm, self.user_transform
+ return map_fn(
+ self.svg.view_box(),
+ self.ufo.info.ascender,
+ self.ufo.info.descender,
+ self.ufo[self.glyph_name].width,
+ self.user_transform,
  )
 
  def transform_for_otsvg_space(self):
- """Creates a Transform to map SVG coords OT-SVG coords"""
- if not self._has_viewbox_for_transform():
- return Affine2D.identity()
- return map_viewbox_to_otsvg_emsquare(
- self.svg.view_box(), self.ufo.info.unitsPerEm, self.user_transform
- )
+ return self._transform(map_viewbox_to_otsvg_space)
+
+ def transform_for_font_space(self):
+ return self._transform(map_viewbox_to_font_space)
 
  def paints(self):
  """Set of Paint used by this glyph."""

src/nanoemoji/config.py

@@ -52,8 +52,8 @@
 flags.DEFINE_string("config", None, "Config file.")
 flags.DEFINE_integer("upem", None, "Units per em.")
 flags.DEFINE_integer("width", None, "Width.")
-flags.DEFINE_integer("ascent", None, "Ascender")
-flags.DEFINE_integer("descent", None, "Descender.")
+flags.DEFINE_integer("ascender", None, "Ascender")
+flags.DEFINE_integer("descender", None, "Descender.")
 flags.DEFINE_string("transform", None, "User transform, in font coordinates.")
 flags.DEFINE_integer("version_major", None, "Major version.")
 flags.DEFINE_integer("version_minor", None, "Minor version.")
@@ -112,9 +112,9 @@ class FontConfig(NamedTuple):
  output_file: str = "AnEmojiFamily.ttf"
  color_format: str = "glyf_colr_1"
  upem: int = 1024
- width: int = 1024
- ascent: int = 950 # default based on Noto Emoji
- descent: int = -250 # default based on Noto Emoji
+ width: int = 1275 # default based on Noto Emoji
+ ascender: int = 950 # default based on Noto Emoji
+ descender: int = -250 # default based on Noto Emoji
  transform: Affine2D = Affine2D.identity()
  version_major: int = 1
  version_minor: int = 0
@@ -137,6 +137,23 @@ def output_format(self):
  def has_picosvgs(self):
  return not self.color_format.startswith("untouchedsvg")
 
+ def validate(self):
+ for attr_name in (
+ "upem",
+ "width",
+ "ascender",
+ "version_major",
+ "version_minor",
+ ):
+ value = getattr(self, attr_name)
+ if value < 0:
+ raise ValueError(f"'{attr_name}' must be zero or positive")
+
+ if self.descender > 0:
+ raise ValueError("'descender' must be zero or negative")
+
+ return self
+
 
 def write(dest: Path, config: FontConfig):
  toml_cfg = {
@@ -145,8 +162,8 @@ def write(dest: Path, config: FontConfig):
  "color_format": config.color_format,
  "upem": config.upem,
  "width": config.width,
- "ascent": config.ascent,
- "descent": config.descent,
+ "ascender": config.ascender,
+ "descender": config.descender,
  "transform": config.transform.tostring(),
  "version_major": config.version_major,
  "version_minor": config.version_minor,
@@ -224,8 +241,8 @@ def load(config_file: Path = None, additional_srcs: Tuple[Path] = None) -> FontC
  color_format = _pop_flag(config, "color_format")
  upem = int(_pop_flag(config, "upem"))
  width = int(_pop_flag(config, "width"))
- ascent = int(_pop_flag(config, "ascent"))
- descent = int(_pop_flag(config, "descent"))
+ ascender = int(_pop_flag(config, "ascender"))
+ descender = int(_pop_flag(config, "descender"))
  transform = _pop_flag(config, "transform")
  if not isinstance(transform, Affine2D):
  assert isinstance(transform, str)
@@ -301,8 +318,8 @@ def load(config_file: Path = None, additional_srcs: Tuple[Path] = None) -> FontC
  color_format=color_format,
  upem=upem,
  width=width,
- ascent=ascent,
- descent=descent,
+ ascender=ascender,
+ descender=descender,
  transform=transform,
  version_major=version_major,
  version_minor=version_minor,
@@ -316,4 +333,4 @@ def load(config_file: Path = None, additional_srcs: Tuple[Path] = None) -> FontC
  axes=tuple(axes),
  masters=tuple(masters),
  source_names=tuple(sorted(source_names)),
- )
+ ).validate()

src/nanoemoji/write_font.py

@@ -145,8 +145,8 @@ def _ufo(config: FontConfig) -> ufoLib2.Font:
  ufo.info.familyName = config.family
  # set various font metadata; see the full list of fontinfo attributes at
  # https://unifiedfontobject.org/versions/ufo3/fontinfo.plist/#generic-dimension-information
- ufo.info.ascender = config.ascent
- ufo.info.descender = config.descent
+ ufo.info.ascender = config.ascender
+ ufo.info.descender = config.descender
  ufo.info.unitsPerEm = config.upem
  # version
  ufo.info.versionMajor = config.version_major