86 lines
2.5 KiB
Python
86 lines
2.5 KiB
Python
"""Draw statistical shape of a glyph as an ellipse."""
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from fontTools.ttLib import TTFont
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from fontTools.pens.recordingPen import RecordingPen
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from fontTools.pens.cairoPen import CairoPen
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from fontTools.pens.statisticsPen import StatisticsPen
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import cairo
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import math
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import sys
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font = TTFont(sys.argv[1])
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unicode = sys.argv[2]
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cmap = font["cmap"].getBestCmap()
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gid = cmap[ord(unicode)]
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hhea = font["hhea"]
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glyphset = font.getGlyphSet()
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with cairo.SVGSurface(
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"example.svg", hhea.advanceWidthMax, hhea.ascent - hhea.descent
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) as surface:
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context = cairo.Context(surface)
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context.translate(0, +font["hhea"].ascent)
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context.scale(1, -1)
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glyph = glyphset[gid]
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recording = RecordingPen()
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glyph.draw(recording)
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context.translate((hhea.advanceWidthMax - glyph.width) * 0.5, 0)
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pen = CairoPen(glyphset, context)
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glyph.draw(pen)
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context.fill()
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stats = StatisticsPen(glyphset)
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glyph.draw(stats)
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# https://cookierobotics.com/007/
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a = stats.varianceX
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b = stats.covariance
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c = stats.varianceY
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delta = (((a - c) * 0.5) ** 2 + b * b) ** 0.5
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lambda1 = (a + c) * 0.5 + delta # Major eigenvalue
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lambda2 = (a + c) * 0.5 - delta # Minor eigenvalue
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theta = math.atan2(lambda1 - a, b) if b != 0 else (math.pi * 0.5 if a < c else 0)
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mult = 4 # Empirical by drawing '.'
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transform = cairo.Matrix()
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transform.translate(stats.meanX, stats.meanY)
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transform.rotate(theta)
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transform.scale(math.sqrt(lambda1), math.sqrt(lambda2))
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transform.scale(mult, mult)
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ellipse_area = math.sqrt(lambda1) * math.sqrt(lambda2) * math.pi / 4 * mult * mult
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if stats.area:
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context.save()
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context.set_line_cap(cairo.LINE_CAP_ROUND)
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context.transform(transform)
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context.move_to(0, 0)
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context.line_to(0, 0)
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context.set_line_width(1)
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context.set_source_rgba(1, 0, 0, abs(stats.area / ellipse_area))
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context.stroke()
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context.restore()
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context.save()
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context.set_line_cap(cairo.LINE_CAP_ROUND)
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context.set_source_rgb(0.8, 0, 0)
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context.translate(stats.meanX, stats.meanY)
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context.move_to(0, 0)
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context.line_to(0, 0)
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context.set_line_width(15)
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context.stroke()
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context.transform(cairo.Matrix(1, 0, stats.slant, 1, 0, 0))
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context.move_to(0, -stats.meanY + font["hhea"].ascent)
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context.line_to(0, -stats.meanY + font["hhea"].descent)
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context.set_line_width(5)
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context.stroke()
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context.restore()
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