Merge pull request #97 from dummy-index/fix/kerning_etc

Fix outline of gamma, fix pad_glyph(), add more kernings with smarter operation

Author: pelson

xkcd-script/font/xkcd-script.otf

@@ -17,6 +17,10 @@
 UPSAMPLE = 12   # upscale factor before potrace; higher = more curve detail
 THRESHOLD = 160  # pixel value below which a pixel is considered ink
 
+SPECIALUPSAMPLE = {
+    'gamma':    8,
+}
+
 
 def _clean_potrace_svg(raw_svg_path, clean_svg_path):
     """Remove potrace artefacts from raw_svg_path and write clean_svg_path.
@@ -79,8 +83,9 @@ def extract_symbol(arr, y0, y1, x0, x1, name, exclude=None):
     if exclude:
         for ey0, ey1, ex0, ex1 in exclude:
             crop[ey0 - y0:ey1 - y0, ex0 - x0:ex1 - x0] = 255
+    upsample = SPECIALUPSAMPLE.get(name, UPSAMPLE)
     big = Image.fromarray(crop).resize(
-        (crop.shape[1] * UPSAMPLE, crop.shape[0] * UPSAMPLE),
+        (crop.shape[1] * upsample, crop.shape[0] * upsample),
         Image.BILINEAR)
     binary = (np.array(big) >= THRESHOLD).astype(np.uint8) * 255
 

xkcd-script/font/xkcd-script.sfd

@@ -18,6 +18,9 @@
 import parse
 import unicodedata
 
+SPACE = 0
+RSPACE = 20
+
 fnames = sorted(glob.glob('../generated/characters/char_*.svg'))
 
 characters = []
@@ -110,6 +113,8 @@ def create_char(font, chars, fname):
     with tmp_symlink(fname) as tmp_fname:
         # At last, bring in the SVG image as an outline for this glyph.
         c.importOutlines(tmp_fname)
+        # Call addExtrema() first to ensure the proper operation of boundingBox().
+        c.addExtrema()
 
     return c
 
@@ -235,51 +240,53 @@ def pad_glyph(c):
     # Put horizontal padding around the glyph. I choose a number here that looks reasonable,
     # there are far more sophisticated means of doing this (like looking at the original image,
     # and calculating how much space there should be).
-    space = 0
-    rspace = 20
-    c.font['_pad_space'].width = space + rspace
+    space = SPACE
+    rspace = RSPACE
     bbox = c.boundingBox()
     if c.glyphname in list('gjpqy'):
         # Recalculate the bounding box by excluding the tail of the glyph
         # Do not remove the glyph's tail if it is too close to the baseline
         capxrange = c.foreground.xBoundsAtY(-40, 600)
         if c.glyphname == 'j':
-            bbox = tuple([(capxrange[0] + bbox[0])/2, bbox[1], capxrange[1], bbox[3]])
+            bbox = tuple([(capxrange[0]*2 + bbox[0])/3, bbox[1], capxrange[1], bbox[3]])
         else:
             bbox = tuple([capxrange[0], bbox[1], capxrange[1], bbox[3]])
     if c.glyphname == 'f':
         # Recalculate the bounding box by excluding the arm of the glyph
         # Restrict the arm so that it does not pierce through the stem of the next glyph
         xxrange = c.foreground.xBoundsAtY(0, 420)
         bbox = tuple([xxrange[0], bbox[1], max(xxrange[1], bbox[2] - (rspace + space + 0.12 * 600)), bbox[3]])
-    lflatness = c.foreground.yBoundsAtX(bbox[0] - 1, bbox[0] + 20)
-    rflatness = c.foreground.yBoundsAtX(bbox[2] - 20, bbox[2] + 1)
+    # Measure the smoothness of a peak when there is one extremum.
+    lflatness = c.foreground.yBoundsAtX(bbox[0] - 20, bbox[0] + 20)
+    rflatness = c.foreground.yBoundsAtX(bbox[2] - 20, bbox[2] + 20)
+    # In the case of a complex shape, the average depth is calculated from measurements taken at four points.
+    # However, for a parabola, this is an algorithm that can accurately determine the coefficient of the quadratic term.
     roughness = []
     for i in range(4):
         roughness.append(c.foreground.xBoundsAtY(100 + 100 * i, 150 + 100 * i) or tuple([bbox[2], bbox[0]]))
-    lroughness = np.sqrt(np.median([(roughness[i][0] - bbox[0])**2 for i in range(4)]))
-    rroughness = np.sqrt(np.median([(bbox[2] - roughness[i][1])**2 for i in range(4)]))
+    lroughness = np.median([np.sqrt(max(roughness[i][0] - bbox[0], 0)) for i in range(4)])**2
+    rroughness = np.median([np.sqrt(max(bbox[2] - roughness[i][1], 0)) for i in range(4)])**2
     add_left = 0
-    if lflatness[1] - lflatness[0] < 0.25 * 600:
+    if lflatness[1] - lflatness[0] < 0.2 * 600:
         add_left = 0
     elif lroughness >= 35:
         add_left = 0
     elif lroughness >= 20:
         add_left = 5
-    elif lroughness >= 10:
+    elif lroughness >= 11:
         add_left = 10
     elif lroughness >= 5:
         add_left = 15
     else:
         add_left = 20
     add_right = 0
-    if rflatness[1] - rflatness[0] < 0.25 * 600:
+    if rflatness[1] - rflatness[0] < 0.2 * 600:
         add_right = 0
     elif rroughness >= 35:
         add_right = 0
     elif rroughness >= 20:
         add_right = 5
-    elif rroughness >= 10:
+    elif rroughness >= 11:
         add_right = 10
     elif rroughness >= 5:
         add_right = 15
@@ -290,9 +297,12 @@ def pad_glyph(c):
         add_right += 10
     may_too_wide1 = list('aebdpr')
     if c.glyphname in may_too_wide1:
-        if bbox[2] - bbox[0] > 370:
-            add_left -= 5
+        if bbox[2] - bbox[0] + add_left + add_right >= 398:
+            add_left -= 10
             add_right -= 10
+        elif bbox[2] - bbox[0] + add_left + add_right >= 378:
+            add_left -= 5
+            add_right -= 5
     scaled_width = bbox[2]
     c.width = round(scaled_width + rspace + space / 2 + add_right)
     t = psMat.translate(round((-bbox[0]) + space / 2 + add_left), 0)
@@ -324,12 +334,16 @@ def charname(char):
 # Information to be conveyed to the next stage.
 # I wanted to use font.persistent, but it causes an error. Instead, I use a dummy glyph.
 font.createChar(-1, '_pad_space')
+font['_pad_space'].width = SPACE + RSPACE
 
 # Per-character size scaling applied after changeWeight, to fine-tune individual glyphs
 # that end up slightly too large despite correct stroke weight.
 _per_char_operation = {
     ('q',): psMat.compose(psMat.scale(0.92), psMat.translate(0, 20)),
     ('x',): psMat.translate(0, 20),
+    ('j',): psMat.translate(0, -20),
+    ('A',): psMat.translate(0, -10),
+    ('N',): psMat.translate(0, -10),
 }
 
 # Per-character weight nudge applied after the per-line scale correction.
@@ -407,7 +421,11 @@ def charname(char):
     # Per-character size adjustments: scale about the baseline (origin) to reduce
     # overall size while preserving stroke weight gained from changeWeight above.
     _operation_matrix = _per_char_operation.get(chars)
-    if _operation_matrix is not None:
+    if chars == ('A',) and c.boundingBox()[1] < 25:
+        pass
+    elif chars == ('N',) and c.boundingBox()[1] < 25:
+        pass
+    elif _operation_matrix is not None:
         c.transform(_operation_matrix)
 
     # Apply padding afterward so that it is not affected by scaling.

xkcd-script/font/xkcd-script.ttf

@@ -66,27 +66,25 @@ def _expand_with_variants(font, chars):
 def autokern(font):
     all_glyphs = [glyph.glyphname for glyph in font.glyphs()
                   if not glyph.glyphname.startswith(' ')]
-    ligatures = [name for name in all_glyphs if '_' in name]
+    ligatures = [name for name in all_glyphs if name[0] != '_' and '_' in name]
     upper_ligatures = [ligature for ligature in ligatures if ligature.upper() == ligature]
     lower_ligatures = [ligature for ligature in ligatures if ligature.lower() == ligature]
 
-    # Expand the broad letter lists to include accented variants from the outset,
-    # so every rule that references `caps`, `lower`, or `all_chars` covers them too.
-    caps = _expand_with_variants(font, list('ABCDEFGHIJKLMNOPQRSTUVWXYZ') + upper_ligatures)
-    lower = _expand_with_variants(font, list('abcdefghijklmnopqrstuvwxyz') + lower_ligatures)
-    all_chars = caps + lower
+    caps = list('ABCDEFGHIJKLMNOPQRSTUVWXYZ')
+    lower = list('abcdefghijklmnopqrstuvwxyz')
+    roman = caps + lower
 
     font.addLookup('kerning', 'gpos_pair', (), [['kern', [['latn', ['dflt']]]]])
     font.addLookupSubtable('kerning', 'kern')
 
-    def kern(sep, left, right, **kwargs):
+    def kern(sep, left, right, damper=None, **kwargs):
         """Wraps font.autoKern: expands accented variants and leading/trailing ligatures."""
         def expand(chars, left_side):
             expanded = _expand_with_variants(font, chars)
             seen = set(expanded)
             for glyph in font.glyphs():
                 name = glyph.glyphname
-                if '_' not in name:
+                if name[0] == '_' or '_' not in name:
                     continue
                 parts = name.split('_')
                 # Left side: ligature's right edge (last component) determines spacing.
@@ -96,26 +94,72 @@ def expand(chars, left_side):
                     expanded.append(name)
                     seen.add(name)
             return expanded
-        font.autoKern('kern', sep, expand(left, left_side=True), expand(right, left_side=False), **kwargs)
+        lefts = expand(left, left_side=True)
+        rights = expand(right, left_side=False)
+        font.autoKern('kern', sep, lefts, rights, **kwargs)
+        if damper and damper != 1.0:
+            for l in lefts:
+                tuples = font[l].getPosSub('kern')
+                new_table = []
+                for tup in tuples:
+                    if tup[1] == 'Pair' and tup[2] in rights:
+                        font[l].addPosSub('kern', *(tup[2:5] + (int(tup[5] * damper),) + tup[6:]))
+
+    def getkern(left, right):
+        c = font[left]
+        tuples = c.getPosSub('kern')
+        for tup in tuples:
+            if tup[1] == 'Pair' and tup[2] == right:
+                return tup[5]
+        return None
 
     a = font['_pad_space'].width
-    a = max(a - 20, 0)
+    a = a - 20
 
+    # The same combination will be overwritten, so the one written last will take effect.
     # autoKern looks at the outline, so even if you change the padding, it absorbs all of it.
     # Use `+a` when you want to link the spacing after kerning to the padding.
     kern(150, ['/', '\\'], ['/', '\\'])
-    kern(60+a, ['s'], set(lower) - {'j', 'f'}, minKern=50)
-    # x has diagonal strokes that leave visual space on its left side.
-    kern(90+a, set(lower) - {'f'}, ['x'], minKern=40)
+    # lowercase-lowercase
+    kern(60+a, ['s'], set(lower) - {'i', 'j', 'f', 't', 'x'}, onlyCloser=True, damper=0.75) # loosen by damper
+    # Overwrite sf and st. (From experience, it is often just right to adopt the larger of the two
+    # separation required by the glyphs on the left and right.)
+    # The horizontal bars of 'r' and 'f' get caught between the dot and the stem of 'i', causing
+    # unexpected behavior, so 'i' and 'j' are excluded.
+    kern(80+a, set(lower) - {'i', 'j'}, ['f', 't'], onlyCloser=True, damper=0.75)
+    kern(90+a, set(lower) - {'i', 'j'}, ['x'], onlyCloser=True, damper=0.75) # kx is fine, fx is tight
+    kern(80+a, ['x'], set(lower) - {'i', 'j'}, onlyCloser=True, damper=0.75)
+    kern(100+a, ['f', 't'], set(lower) - {'i', 'j'}, onlyCloser=True, damper=0.75) # oveerwrite fx
+    # For some reason, autoKern malfunctions on the left side of 'e', so the kerning value of 'o' is reused.
+    kern(0, ['r'], ['e', 'o'])
+    diff_ro_re = getkern('r', 'o') - getkern('r', 'e')
+    kern(100+a, ['r'], set(lower) - {'i', 'j'}, onlyCloser=True, damper=0.75)
+    kern(100+a + diff_ro_re, ['r'], ['e'], onlyCloser=True, damper=0.75)
+    # including uppercase
+    # Set *Y altogether first: CY, OY, etc. will have appropriate values set in the latter part.
+    kern(105+a, roman, ['Y', 'T'], onlyCloser=True, damper=0.75)
+    kern(100+a, caps, ['f'], onlyCloser=True, damper=0.75)
     # F/E are separated from T/J so they can use a tighter target gap.
-    kern(130, ['F'], set(all_chars) - {'f', 'j'})
-    kern(140, ['E'], ['V', 'W', 'Y'])
-    kern(100, ['E'], set(all_chars) - {'f', 'j'})
-    kern(120, ['T', 'J'], ['R'])
-    kern(150, ['T', 'J'], set(all_chars) - {'f', 'j'})
-    # C: loosen from the default (was too tight for Ct/Cf/Cj).
-    kern(65, ['C'], set(all_chars) - {'f', 'j'})
-    kern(60, ['O'], set(all_chars) - {'f', 'j'})
+    kern(110+a, ['F'], set(roman) - {'j'}, onlyCloser=True, damper=0.75) # keep FO≈-60
+    # Since F and z mesh together and the kerning becomes too large,
+    # reuse the kerning value of one of the round letterforms.
+    diff_Fo_Fz = getkern('F', 'o') - getkern('F', 'z')
+    kern(110+a + int(diff_Fo_Fz / 0.75), ['F'], ['z'], onlyCloser=True, damper=0.75)
+    kern(90+a, ['E'], set(roman) - {'j'}, onlyCloser=True, damper=0.75) # keep ES≈-30
+    kern(45+a, ['E'], ['V'], onlyCloser=True, touch=True)
+    kern(115+a, ['T', 'J'], set(roman) - {'j'}, onlyCloser=True, damper=0.75) # keep Tr≈-105
+    kern(105+a, ['Y'], set(roman) - {'j'}, onlyCloser=True, damper=0.75)
+    kern(85+a, ['V'], caps, onlyCloser=True, damper=0.75)
+    # C: loosen from the default (was too tight for Cj).
+    # Compared to E, the lower curve of C tends to come close to the next character,
+    # but this is considered an intentional design.
+    kern(60+a, ['C'], set(roman) - {'j'}, onlyCloser=True, damper=0.75) # keep CK≈-15
+    kern(25+a, ['C'], ['V'], onlyCloser=True, touch=True)
+    kern(60+a, ['O'], set(roman) - {'j'}, onlyCloser=True, damper=0.75) # loosen
+    kern(100+a, ['P'], set(roman) - {'j'}, onlyCloser=True, damper=0.75)
+    diff_Po_Pe = getkern('P', 'o') - getkern('P', 'e')
+    kern(100+a + int(diff_Po_Pe / 0.75), ['P'], ['e'], onlyCloser=True, damper=0.75)
+    kern(35+a, ['L'], set(roman) - {'j'}, onlyCloser=True, touch=True)
 
 
 autokern(font)
@@ -208,7 +252,7 @@ def expand(chars, left_side):
 # hinting, which alters the rendered pixel positions of Latin letters.  Pin
 # all values here (derived from the Latin+diacritic glyph set) so the
 # hinting is stable regardless of how many non-Latin glyphs are added.
-font.private['BlueValues'] = (-20, 20, 411, 450, 573, 613)
+font.private['BlueValues'] = (-10, 20, 411, 441, 573, 603)
 font.private['OtherBlues'] = (-241, -190)
 font.private['BlueScale'] = 0.0208333
 font.private['BlueShift'] = 16