The .ELI/.WPI binary format is a serialized binary format representing pen data, including position, tilt, pressure, timing, strokes, layers, and more.

This specification is unofficial, incomplete, in progress and the result of trial and error, a hex editor, and a handful of .WPI files carefully generated with the Wacom Inkling.

Christopher Baker https://christopherbaker.net

Equipment

Wacom Inkling

The Wacom Inkling's official specifications can be found here. It appears that the sampling rate for the Inkling is 200 samples / second. It provides 1024 levels of pressure.

Others

…

Header

The standard header length is 2059 bytes. There are some variations between headers, but no examples have exceeded 2059 bytes. The contents are still a work in progress.

Byte_Range	Function	Notes
0-269	…	…
270-273	…	differ across devices ?
270-273	…	differ across devices ?
334-337	…	differ across devices ?
434-436	…	differ across devices ?
446-1136	…	differ across devices ?
1146-1837	…	differ across devices ?
1858-1860	…	differ across devices ?
1870-1871	…	differ across devices ?
1882-1885	…	differ across devices ?
1894-1897	…	differ across devices ?
2043-2044	…	differ across devices ?
2045-2059	…	Are again the same.

Layer and Stroke Blocks

Layer and stroke blocks are 3 bytes long and are indicated by a 0xF1 marker, and a block identification byte differentiating the specific event types.

Layer Start Block

A new layer is indicated by block identification of 0x80.

BYTE_0	BYTE_1	BYTE_2
Marker	Length	ID
`0xF1`	`0x03`	`0x80`

Notes

Stroke Start Block

The beginning of a stroke (a pen down) is indicated by 3 byte sequence.

BYTE_0	BYTE_1	BYTE_2
Marker	Length	ID
`0xF1`	`0x03`	`0x01`

Stroke End Block

The end of the stroke (a pen lift) is indicated by a 3 byte sequence.

BYTE_0	BYTE_1	BYTE_2
Marker	Length	ID
`0xF1`	`0x03`	`0x00`

Pen Data Blocks

Wacom Inkling .WPI files generally present pen data in clusters of three ordered data points. These clusters are always surrounded by Stroke Start and Stroke End events.

Example

X/Y POSITION Block

X and Y values are encoded as a two byte uint16_t values.

BYTE_0	BYTE_1	BYTE_2	BYTE_3	BYTE_4	BYTE_5
Marker	Length	X HIGH	X LOW	Y HIGH	Y LOW
`0xF1`	`0x06`	`VARIES`	`VARIES`	`VARIES`	`VARIES`

Example

uint8_t  buffer[] = { 0x61, 0x06, 0x03, 0x4F, 0x13, 0x61 };
uint32_t i = 0;
uint16_t xPos = (buffer[i+2] << 8) | (buffer[i+3]); // get x value
uint16_t yPos = (buffer[i+4] << 8) | (buffer[i+5]); // get y value

Notes

float x = xPos / 10.0f; // Scale like Inkling Sketch Manager
float y = xPos /  5.0f; // Scale like Inkling Sketch Manager

This scaling factor was empirically determined by comparing the raw .WPI file output to Wacom's Sketch Manager .WAC InkML files.

X/Y TILT Block

Tilt X and Tilt Y values are encoded as a one byte uint8_t values.

BYTE_0	BYTE_1	BYTE_2	BYTE_3	BYTE_4	BYTE_5
Marker	Length	X TILT	Y TILT	?	?
`0x65`	`0x06`	`VARIES`	`VARIES`	`0x00`‡	`0x00`‡

Example

uint8_t  buffer[] = { 0x65, 0x06, 0x3D, 0x28 0x00, 0x00 };
uint32_t i = 0;
int8_t   xTilt = buffer[i+2];  // get tilt x value
int8_t   yTilt = buffer[i+3];  // get tilt y value

Notes

PRESSURE

Pressure is encoded as a two byte uint16_t value. Pressure values range between 0-1024 based on the specifications.

BYTE_0	BYTE_1	BYTE_2	BYTE_3	BYTE_4	BYTE_5
Marker	Length	?	?	PRES. HIGH	PRES. LOW
`0x64`	`0x06`	`0x00`‡	`0x00`‡	`VARIES`	`VARIES`

Example

uint8_t  buffer[] = { 0x64, 0x06, 0x00, 0x00, 0x00, 0xAD };
uint32_t i = 0;
uint16_t pressure = (buffer[i+4] << 8) | (buffer[i+5]); // get pressure

Notes

Time

Timing blocks begin with a 0xC2 are 0x06 bytes long and are identified by a block id, depending on the type of counter information. The most important timer is the Clock.

Clock

Throughout each file, a time marker is recorded every second beginning with device power on. They are identified by a block id of 0x11. The timing sequence is composed of 6 bytes. The elapsed time is encoded in the last two bytes as an uint16_t. BYTE_3 may also be used to encode time, but the last two bytes can represent 2⁸ seconds (over 18 hours). No test data of this duration has been generated.

BYTE_0	BYTE_1	BYTE_2	BYTE_3	BYTE_4	BYTE_5
Marker	Length	ID	?	COUNTER HIGH	COUNTER LOW
`0xC2`	`0x06`	`0x11`	`0x00`‡	`VARIES`	`VARIES`

Example

uint8_t  buffer[] = { 0xC2, 0x06, 0x11, 0x00, 0x00, 0x01 };
uint32_t i = 0;
uint16_t counter = (buffer[i+4] << 8) | (buffer[i+5]); // get counter value

Notes

Clock "Init" INCOMPLETE

The clock "init" block happens early in all files examined -- usually before the first Clock block. They are identified by a block id of 0x00. Usually this block ends with a 0x01, but when multiples are present in longer files, the last byte can be a 0x02. Usually this byte alternates between 0x01 and 0x02 when multiples are present. It does not seem to affect or respond other timer values.

BYTE_0	BYTE_1	BYTE_2	BYTE_3	BYTE_4	BYTE_5
Marker	Length	ID	?	?	Alternates b/t 0x01/0x02
`0xC2`	`0x06`	`0x00`	`0x00`‡	`0x00`‡	`0x01, 0x02`‡

Clock "Unknown" INCOMPLETE

The clock "unknown" block usually only happens once per file. It is usually located near the beginning of the file. They are identified by a block id of 0x12. The last two bytes often share values between files, but not consistently. The range of values taken by the last two bytes are fairly limited, matching occasionally, but not in a clear pattern. It is possible that the last two bytes should be read as a int16_t or uint16_t.

BYTE_0	BYTE_1	BYTE_2	BYTE_3	BYTE_4	BYTE_5
Marker	Length	ID	?	?	?
`0xC2`	`0x06`	`0x12`	`0x00`‡	`VARIES`	`VARIES`

Quality / Control Blocks

Interference / Obstructions

The interference sequence occurs when an object is placed in front of the sensor. While the obstruction is present, bytes 10 and 11 are incremented, perhaps representing a counter. Note that unlike position values (which are Big Endian), the counter value appears to be Little Endian.

BYTE_0	BYTE_1	BYTE_2	BYTE_3	BYTE_4	BYTE_5	BYTE_6	BYTE_7
Marker	Length	?	?	?	?	?	?
`0xC7`	`0x0E`	`0x04`‡	`0x04`‡	`0x03`‡	`VARIES`	`VARIES`	`VARIES`

BYTE_8	BYTE_9	BYTE_10	BYTE_11	BYTE_12	BYTE_13
?	?	COUNTER LOW	COUNTER HIGH	?	?
`VARIES`	`VARIES`	`VARIES`	`VARIES`	`0x00`‡	`0x00`‡

0xC7, 0x1E INCOMPLETE

BYTE_0	BYTE_1	BYTE_2	BYTE_3	BYTE_4	BYTE_5	BYTE_6	BYTE_7
Marker	Length (30)	?	?	?	?	?	?
`0xC7`	`0x1E`	`0x05 or 0x03`‡	`0x04 or 0x02`‡	`0x00`‡	`0x00`‡	`0x07`‡	`0x00`‡

BYTE_8	BYTE_9	BYTE_10	BYTE_11	BYTE_12	BYTE_13	BYTE_14	BYTE_15
?	?	?	COUNTER LOW	COUNTER HIGH	?	?	?
`0x00`‡	`0x00`‡	`VARIES`	`VARIES`	`VARIES`	`0x00`‡	`0x00`‡	`0x00`‡

BYTE_16	BYTE_17	BYTE_18	BYTE_19	BYTE_20	BYTE_21	BYTE_22	BYTE_23
?	?	?	?	?	?	?	?
`0x00`	`0x00`	`0x00`‡	`0x00`‡	`0x00`‡	`0x00 OR 0x01`‡	`0x00`‡	`0x00`‡

BYTE_24	BYTE_25	BYTE_26	BYTE_27	BYTE_28	BYTE_29
?	?	?	?	?	?
`0x00`‡	`0x00 OR 0x01`‡	`0x00`‡	`0x00`‡	`0x00`‡	`0x00`‡

Notes

0xC7, 0x1A INCOMPLETE

Notes

0xC7, 0x16 INCOMPLETE

Notes

0xC7, 0x22 INCOMPLETE

Notes

e.g. c7,0e,04,04,00,00,03,00,00,00,4a,2a,00,00w

0xC7, 0x0E, 0x00

///////////////// The "0xC513" sequence happens through the file. The file always ends with a "0xC513" sequence and the very last one last byte in the last "0xC513" sequence is always a 0x02.

e.g. 0xC5 0x13 0x00 0x4A 0xCD 0x59 0x03 0x03 0x01 0x94 0x04 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00

e.g. last "0xC513" seq. 0xC5 0x13 0x00 0x6E 0xCD 0x59 0x03 0x06 0x01 0xB6 0x04 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x02

The "0xC71E" sequence usually happens early in the file, but can happen elsewhere. It is usually (but not always) closely followed by a "0xC71A" sequence (below).

e.g. 0xC7 0x1E 0x03 0x02 0x00 0x00 0x07 0x00 0x00 0x00 0xE2 0x0C 0x00 0x00 0x00 0x80 0x00 0x00 0x00 0x00 0x00 0x00 0x01 0x00 0x00 0x00 0x01 0x00 0x00 0x00

The "0xC71A" sequence always follows a "0xC71E" sequence.

e.g. 0xC7 0x1A 0x04 0x02 0x00 0x00 0x06 0x00 0x00 0x00 0x06 0x0D 0x00 0x00 0x00 0x80 0x00 0x00 0x00 0x00 0x00 0x00 0x02 0x00 0x00 0x00

Footnotes

test dcc
* :
** : -
† :
‡ : Typical Value - could take other values, but no other values have been observed.
§ : -
Incomplete : Incomplete - more data needed.

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Equipment

Wacom Inkling

Others

Header

Layer and Stroke Blocks

Layer Start Block

Notes

Stroke Start Block

Stroke End Block

Pen Data Blocks

Example

X/Y POSITION Block

Example

Notes

X/Y TILT Block

Example

Notes

PRESSURE

Example

Notes

Time

Clock

Example

Notes

Clock "Init" INCOMPLETE

Clock "Unknown" INCOMPLETE

Quality / Control Blocks

Interference / Obstructions

0xC7, 0x1E INCOMPLETE

Notes

0xC7, 0x1A INCOMPLETE

Notes

0xC7, 0x16 INCOMPLETE

Notes

0xC7, 0x22 INCOMPLETE

Notes

Footnotes

FilesExpand file tree

ELI_FileSpec.md

Latest commit

History

ELI_FileSpec.md

File metadata and controls

Equipment

Wacom Inkling

Others

Header

Layer and Stroke Blocks

Layer Start Block

Notes

Stroke Start Block

Stroke End Block

Pen Data Blocks

Example

X/Y POSITION Block

Example

Notes

X/Y TILT Block

Example

Notes

PRESSURE

Example

Notes

Time

Clock

Example

Notes

Clock "Init" INCOMPLETE

Clock "Unknown" INCOMPLETE

Quality / Control Blocks

Interference / Obstructions

0xC7, 0x1E INCOMPLETE

Notes

0xC7, 0x1A INCOMPLETE

Notes

0xC7, 0x16 INCOMPLETE

Notes

0xC7, 0x22 INCOMPLETE

Notes

Footnotes