Module: Fontisan::Ufo::Compile::Filters::CubicToQuadratic

Defined in:
lib/fontisan/ufo/compile/filters/cubic_to_quadratic.rb

Overview

Converts cubic Bezier curves to quadratic. TrueType outlines only support quadratic Beziers; UFO sources typically use cubic. This filter walks each contour, finds cubic segments (two consecutive off-curve points followed by an on-curve), and replaces them with one or more quadratic approximations.

Algorithm (fontTools-compatible):

For cubic (P0, C1, C2, P3):
Q1 = (3*C1 - P0) / 2
Q2 = (3*C2 - P3) / 2
Q  = midpoint(Q1, Q2)
Error ≈ |Q1 - Q2| / 3
If error ≤ tolerance: emit one quadratic (P0, Q, P3)
Else: subdivide at t=0.5, recurse each half.

Constant Summary collapse

DEFAULT_TOLERANCE = 
1.0

Class Method Summary collapse

Class Method Details

.run(glyphs, tolerance: DEFAULT_TOLERANCE, **_opts) ⇒ Array<Fontisan::Ufo::Glyph>

Returns the same array, mutated.

Parameters:

  • glyphs (Array<Fontisan::Ufo::Glyph>)
  • tolerance (Float) (defaults to: DEFAULT_TOLERANCE) —

    max deviation in font units

Returns:



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# File 'lib/fontisan/ufo/compile/filters/cubic_to_quadratic.rb', line 27

def self.run(glyphs, tolerance: DEFAULT_TOLERANCE, **_opts)
  glyphs.each do |glyph|
    glyph.contours.each_with_index do |contour, _ci|
      contour.points = convert_contour(contour.points, tolerance)
    end
  end
  glyphs
end