Create a font from a scanned alphabet
A scanned alphabet sheet is the most reliable way to build a font from drawn letterforms, because a scanner gives you something a camera never quite does: perfectly even light and no perspective. The remaining work is in how you lay the sheet out.
Lay the sheet out for the segmenter
Characters are found by looking for horizontal bands of ink separated by empty space, then splitting each band into characters at the vertical gaps. Everything that makes that easier makes your font better.
The most common cause of a bad conversion is a row where the gaps between letters are smaller than the gaps inside a letter. An H has a wide internal gap; if your letters are set tighter than that gap, the split becomes genuinely ambiguous.
- Leave generous vertical space between rows — more than the tallest ascender.
- Leave horizontal space between characters that is clearly wider than any gap inside a character.
- Keep one kind of letter per row where you can. A row mixing tall capitals and small lowercase has two different natural widths, which makes the spacing estimate a compromise between them.
- Do not let descenders from one row overlap the tops of the next row.
- Keep the sheet free of stray marks, coffee rings, staple holes and printed rules.
Scanner settings that matter
Scan at 300 dpi. Higher resolutions rarely improve the trace and make everything slower; lower resolutions lose the fine ends of strokes.
Scan in greyscale rather than colour, and rather than the scanner's own black-and-white mode. Greyscale keeps the soft edge of each stroke, which is what the threshold uses to place the boundary precisely. The scanner's bilevel mode throws that information away using its own threshold, which you cannot tune afterwards.
Turn off automatic contrast, descreening, dust removal and sharpening. Sharpening in particular adds a bright halo just outside every stroke, which shifts the apparent edge.
Close the lid. An open lid on a thin sheet lets room light through the paper and lifts the background unevenly.
Converting the sheet
Drop the scan in and let it run. The rows are detected, the characters split, and the sequence you type is assigned to the cells in reading order. If the row and character counts do not agree with what you told it to expect, the review step opens rather than the tool reporting a clean result.
Fixing a sheet that segmented badly
Two failures account for most bad sheets, and both are fixable without redrawing anything.
Letters merged into one cell
Two adjacent characters were closer than the natural gaps inside them. Re-scan with the letters further apart if you can. If the sheet is fixed, raising background removal sometimes opens a thin bridge of ink that was joining them.
One letter split into two cells
A character with a genuine internal gap — a lower case i, a colon, a quotation mark, or a wide-legged K — was read as two. Increasing detail keeps small pieces that might otherwise be discarded; the review step is where you confirm what belongs together.
A note on mixed-height rows
A single row that mixes cap-height and lowercase letters cannot be described by one character width. Capitals set a wide advance and lowercase needs a narrower one, so the estimate lands between them and both look slightly wrong. Splitting capitals and lowercase into separate rows avoids the problem entirely and takes no extra paper.
Questions
- What resolution should I scan at?
- 300 dpi greyscale. It has enough detail for clean outlines without slowing everything down.
- Should I use my scanner's black and white mode?
- No. It applies its own threshold and discards the grey edge information that produces precise outlines. Scan greyscale and let the converter place the threshold.
- Can I scan several sheets and combine them?
- Convert each sheet separately and assign each glyph its code point. Keeping the light and the pen consistent between sheets matters more than doing it in one pass.
