HarikomiMaker

Summary

To saddle-stitch a booklet, the pages have to be re-seated in folding order. HarikomiMaker does that arithmetic for a PDF, draws crop and centre marks, and exports a print-ready file.

0

dependencies

Swift, SwiftUI, PDFKit, Core Graphics only

A4–A0

paper sizes

757

lines of Swift

across 7 files

A tool for myself — problem, interface, imposition maths, PDF rendering

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Overview

In saddle stitching, page 1 and the last page are printed on the same sheet. The page count must be a multiple of four, and for the order to come out right after folding, every sheet's front and back needs its own arrangement. The app does that arithmetic.

Key decisions

1. 01Never scale the original; refuse instead

   In print, enlarging by one percent is a different format. Quietly fixing it is the more dangerous option.

   →If the original plus its marks won't fit the sheet, preview and export stop, and the overflow is shown as numbers.

2. 02Take the smallest valid box as the trim size

   Many PDFs leave the TrimBox unset and keep the real finished size in the CropBox.

   →Of Trim, Crop, Bleed and Media, the smallest valid box becomes the reference.

3. 03Preview and export run the same code

   A preview that differs from the output is worse than none.

   →One function serves both.

4. 04Fix the page order as a formula

   The rule is exact; doing it by eye is how it goes wrong.

   →Round the count up to a multiple of four; sheet i carries (total − 2i) and (1 + 2i) on the front, (2 + 2i) and (total − 2i − 1) on the back. Missing pages stay blank.

Output

Sheets exported by the app itself: the original page on the left, and the imposed sheets that fold and staple into order.

Reflection

• A tool should be able to refuse. Stopping and saying why is kinder, in print, than silently making it fit.
• Still to do — a bug that closes the PDF context after the first sheet on longer documents, 4-up layouts, and bleed handling.