The JEF Format: A City Map for a Janome Embroidery Machine

JEF is the native format of Janome embroidery machines. It has no lines, curves or layers in the usual sense: only a sequence of commands to the needle — "step here and stitch", "jump without stitching", "trim the thread", "change colour". A map in such a file is the route of the needle. Below is what sits inside JEF and how our exporter turns streets and rivers into a running stitch.

What is inside JEF

The file starts with a binary header: hoop size, colour count, design extents and the thread table. JEF does not store colours as RGB numbers but as indices into the standard Janome thread palette — the machine and the software pick the nearest thread. After the header come the stitches: needle offsets in tenths of a millimetre plus control commands (jump, trim, colour change, end).

The format's limits are physical. The hoop defines where the needle can be at all. A stitch cannot be arbitrarily long: a long thread sags and snags. Every colour change stops the machine for manual rethreading.

How a map becomes stitches

Our exporter builds the pattern with the pyembroidery library and writes it as JEF. Step by step:

Scaling to the hoop. The whole order area is fitted into the hoop, 200×200 mm by default, with a 5% margin on every side. Proportions are kept: an elongated area fills the hoop along its long side.

Outline stitching. Every line — road, river, boundary — is sewn with a running stitch. Every area — building, lake, park — is sewn along its outer outline. There is no satin fill: this is outline embroidery, a city drawn in thread. Holes inside areas (a courtyard inside a block) are not stitched.

Density. Four stitches are placed per millimetre of path. A segment longer than 12.1 mm is split automatically — that is the hardware stitch-length limit beyond which the machine refuses to sew.

Travel. The needle does not drag thread across the whole map between separate objects: a trim and a jump to the start are placed before every new outline.

Points. A single point object is embroidered as a small cross.

Colours. Each layer gets its own thread: water light blue, waterways a darker blue, greenery green, buildings brown, roads dark grey, railways charcoal, boundaries red, land use tan. A layer without its own colour is sewn in black.

If the pattern comes out empty (no objects in the area), no file is delivered at all — an empty JEF is of no use to a machine.

Before you sew

1. Open the file in your embroidery software and check the stitch count and colour changes. A whole city is tens of thousands of stitches; a small district sews faster and cleaner.
2. Drop extra layers. Embroidery is usually fine with water, roads and boundaries; buildings over a large area merge into solid hatching.
3. Check the hoop. If your machine's hoop is smaller than 200×200 mm, scale the design down in the software before loading it into the machine.
4. Choose threads: a Janome palette index is only the nearest colour, not a design decision.

JEF, DST or PES

JEF is for Janome machines. For industrial Tajima machines take DST, for Brother and Babylock — PES. Our stitch path is built the same way for all three; only the packaging into the file differs. If you need a drawing for your own digitising rather than stitches, take SVG and digitise the outlines in your embroidery editor.