PEC section

The first part of the PEC section is 512 bytes.

Type	Bytes	Value	Description
char	19		Label string prefixed with "LA:" and padded with space (0x20)
char	1	'\r'	carriage return character
u8	11	0x20 (typical)	Unknown
u8	1	0x20 | 0xFF | ?	Unknown
u16	2	0x00FF (typical)	Unknown
u8	1	6 (typical)	Thumbnail image width in bytes, with 8 bit pixels per byte, so 6 would mean 6×8 = 48 pixels per line
u8	1	38 (typical)	Thumbnail image height in pixels
u8	12	0x00 | 0x20 | 0x64 | 0xFF | ?	Unknown, usually 20 20 20 20 64 20 00 20 00 20 20 20
u8	1	N	Number of colors minus one, 0xFF means 0 colors.
u8	1 + N		Palette index
u8	462 - N	0x20 (typical)	Unknown

Then follows the second part of the PEC section.

Type	Bytes	Value	Description
u16	2	0x0000 (typical)	Unknown
u16	2		Offset to thumbnail image subsection relative to the PEC section offset plus 512 bytes
u16	2	0x3100 (typical)	Unknown
u16	2	0xF0FF (typical)	Unknown
s16	2		Width
s16	2		Height
u16	2	0x01E0 (typical)	Unknown
u16	2	0x01B0 (typical)	Unknown
	4		Unknown
pec_stitch_list			PEC stitch list subsection
pec_thumbnail_images			PEC thumbnail image subsection

PEC stitch list subsection

The PEC stitch list come in dx and dy relative coordinate pairs. Depending on the bit patterns used, 2, 3 or 4 bytes are used for the coordinate pairs as explained below. Note that if the first coordinates are (0, 0) the embroidery machine apparently ignores them. The first nonzero coordinate pair is relative to the minimum bound coordinates.

Type	Bytes	Value	Description
u8	1		Stitch dx coordinate
u8	1		Stitch dy coordinate

Some combined dx and dy values have special meaning. After a stop stitch, an alternating byte of 2 and 1 is encoded, starting with 2. The end of the stitch list is coded with 0xFF for dx but no value for dy. To encode a stop stitch, dx is 0xFE.

If the most significant bit is cleared but dx or dy is greater than 0x3F, then their value is subtracted by 0x80 to yield a negative value, respectively.

If the most significant bit is set in dx, the following is computed. If bit 6 is set the stitch is a trim stitch, or if bit 5 is set then the stitch is a jump stitch. The 4 least significant bits in dx are masked and multiplied by 256 and dy is added to dx to yield a 12 bit dx. If dx is greater than 0x7FF then the value is subtracted by 0x1000 to yield a negative value. A following u8 byte is used for a new dy value.

If the most significant bit is set in dy, the following is computed. If bit 6 is set the stitch is a trim stitch, or if bit 5 is set then the stitch is a jump stitch. The 4 least significant bits in dy are masked and multiplied by 256 and the following u8 byte is added to dy to yield a 12 bit dy. If dy is greater than 0x7FF then the value is subtracted by 0x1000 to yield a negative value.

PEC thumbnail image subsection

There is always one main thumbnail image plus one for each color. The size of each thumbnail is the thumbnail width multiplied with the thumbnail height number of bytes (width and height are given in the PEC section). The pixels are oriented from the top left corner, with one pixel per bit starting with the most significant bit in the first byte.