SEW

Status

Field	Value
Extension(s)	.sew
Common ecosystem	Older Janome / Elna / Kenmore
Format family	Machine-specific stitch file
Satin Studio status	Researching
Open / import	No
Export	No
Confidence	Medium.

What it is

SEW is an older Janome-family format used by some Janome, Elna, and Kenmore machines.

Satin Studio direction

Useful as legacy import if files are available. Export would need strict size and stitch-count checks.

Versions and variants

SEW is a legacy Janome-family format. Machine-generation limits such as hoop size and stitch count need to be tracked with version or machine notes.

File identification notes

Reported structure uses signed x, y movement records, x == 0x80 control events, and color lookup through a fixed/magic-number thread table rather than arbitrary RGB metadata.

Observed structure notes

• Observed SEW files start with a little-endian color count and 16-bit color indexes into a fixed Janome-family palette.
• Observed readers seek to offset 0x1D78 for stitch data. Normal movement is signed two-byte dx, dy; first byte 0x80 introduces a control byte plus two payload bytes.
• Observed controls: low bit set means color change, 0x04 or 0x02 jump with payload movement, and 0x10 stitch/control marker with payload movement.
• Observed SEW stitch import depends on a fixed stitch-data offset; header bytes before 0x1D78 carry palette and machine metadata that remain underdocumented.

Structure sketch

Observed SEW files contain palette indexes and a fixed stitch-data offset:

struct SewFile<'a> {
    color_count: u16,
    palette_indexes: &'a [u16],
    padding_until_stitches: &'a [u8],   // stitch stream observed at offset 0x1D78
    records: &'a [SewRecord],
}

enum SewRecord {
    Stitch { dx: i8, dy: i8 },
    ColorChange,                       // marker 0x80, control bit 0x01 set
    Jump { dx: i8, dy: i8 },            // marker 0x80, control 0x04 or 0x02
    StitchControl { dx: i8, dy: i8 },   // marker 0x80, control 0x10
}

What we still need

Old-machine files, exact command mapping, thread lookup table behavior, and documented machine limits.