Font Subsetting for Velvetcache.org

README.md

This script is used to patch and subset the Source Code Pro font for use on my blog.

More details are available at velvetcache.org/2024/02/12/box-drawing-on-the-web

patch-and-subset.sh

UNICODES=(
  "U+0020-007E" # ASCII Printables
  "U+00A1-00BF" # Latin-1 symbols
  "U+00D7"      # Multiplication sign
  "U+00F7"      # Division sign
  "U+2000-206F" # General Punctuation
  "U+2190-21FF" # Arrows
  "U+2200-22FF" # Mathematical Operators
  "U+2500-257F" # Box Drawing
)

unicodes_string="${UNICODES[*]}"

echo "Patching"

python patch-font.py

echo "Subsetting"

rm -f SourceCodePro-Regular-subset*.woff2
rm -f source-code-pro-*.css

pyftsubset SourceCodePro-Regular-patched.ttf \
  --output-file="SourceCodePro-Regular-subset.woff2" \
  --flavor=woff2 \
  --no-hinting \
  --desubroutinize \
  --layout-features="ccmp" \
  --unicodes="${unicodes_string//${IFS:0:1}/,}"

SHA=$(sha256sum SourceCodePro-Regular-subset.woff2 | head -c 7)

mv SourceCodePro-Regular-subset.woff2 "SourceCodePro-Regular-subset-$SHA.woff2"

cat > "source-code-pro-$SHA.css" <<EOF
@font-face {
  font-family: 'Source Code Pro';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url('SourceCodePro-Regular-subset-$SHA.woff2') format('woff2');
}
EOF

echo "-> SourceCodePro-Regular-subset-$SHA.woff2"
echo "-> source-code-pro-$SHA.css"

patch-font.py

from fontTools import ttLib

tt = ttLib.TTFont("SourceCodePro-Regular.ttf")

for table in tt["cmap"].tables:
    if table.platformID == 0:
        if table.cmap[0x25CA] == "lozenge":
            print("Patching table", table.platformID, table.platEncID)
            table.cmap[0x22C4] = "lozenge"

tt.save("SourceCodePro-Regular-patched.ttf")

requirements.txt

Brotli==1.1.0
fonttools==4.48.1
zopfli==0.2.3