blob: 7c2e85c830abee795dda2c680c3d91938eab74f3 [file] [log] [blame]
 """Pen calculating area, center of mass, variance and standard-deviation, covariance and correlation, and slant, of glyph shapes.""" from __future__ import print_function, division, absolute_import from fontTools.misc.py23 import * import math from fontTools.pens.momentsPen import MomentsPen __all__ = ["StatisticsPen"] class StatisticsPen(MomentsPen): """Pen calculating area, center of mass, variance and standard-deviation, covariance and correlation, and slant, of glyph shapes. Note that all the calculated values are 'signed'. Ie. if the glyph shape is self-intersecting, the values are not correct (but well-defined). As such, area will be negative if contour directions are clockwise. Moreover, variance might be negative if the shapes are self-intersecting in certain ways.""" def __init__(self, glyphset=None): MomentsPen.__init__(self, glyphset=glyphset) self.__zero() def _closePath(self): MomentsPen._closePath(self) self.__update() def __zero(self): self.meanX = 0 self.meanY = 0 self.varianceX = 0 self.varianceY = 0 self.stddevX = 0 self.stddevY = 0 self.covariance = 0 self.correlation = 0 self.slant = 0 def __update(self): area = self.area if not area: self.__zero() return # Center of mass # https://en.wikipedia.org/wiki/Center_of_mass#A_continuous_volume self.meanX = meanX = self.momentX / area self.meanY = meanY = self.momentY / area # Var(X) = E[X^2] - E[X]^2 self.varianceX = varianceX = self.momentXX / area - meanX**2 self.varianceY = varianceY = self.momentYY / area - meanY**2 self.stddevX = stddevX = math.copysign(abs(varianceX)**.5, varianceX) self.stddevY = stddevY = math.copysign(abs(varianceY)**.5, varianceY) # Covariance(X,Y) = ( E[X.Y] - E[X]E[Y] ) self.covariance = covariance = self.momentXY / area - meanX*meanY # Correlation(X,Y) = Covariance(X,Y) / ( stddev(X) * stddev(Y) ) # https://en.wikipedia.org/wiki/Pearson_product-moment_correlation_coefficient correlation = covariance / (stddevX * stddevY) self.correlation = correlation if abs(correlation) > 1e-3 else 0 slant = covariance / varianceY self.slant = slant if abs(slant) > 1e-3 else 0 def _test(glyphset, upem, glyphs): from fontTools.pens.transformPen import TransformPen from fontTools.misc.transform import Scale print('upem', upem) for glyph_name in glyphs: print() print("glyph:", glyph_name) glyph = glyphset[glyph_name] pen = StatisticsPen(glyphset=glyphset) transformer = TransformPen(pen, Scale(1./upem)) glyph.draw(transformer) for item in ['area', 'momentX', 'momentY', 'momentXX', 'momentYY', 'momentXY', 'meanX', 'meanY', 'varianceX', 'varianceY', 'stddevX', 'stddevY', 'covariance', 'correlation', 'slant']: if item[0] == '_': continue print ("%s: %g" % (item, getattr(pen, item))) def main(args): if not args: return filename, glyphs = args[0], args[1:] if not glyphs: glyphs = ['e', 'o', 'I', 'slash', 'E', 'zero', 'eight', 'minus', 'equal'] from fontTools.ttLib import TTFont font = TTFont(filename) _test(font.getGlyphSet(), font['head'].unitsPerEm, glyphs) if __name__ == '__main__': import sys main(sys.argv[1:])