GSD

The GSD binary file format

This is my first try to reverse engineer a binary file format. If you like, you could add your thoughts! By comparison between different files with the extention .gsd i try to see what data is stored where. It has some parts in ansi-text and the most parts are just binary numbers of different length. As identification, the file starts with the text "GRAPHTEC PRT&CUT". The next line at offset 0000:0010 starts with binary numbers "03 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00" (I don't know if they make any sense there).

• From offset 0000:0080 to offset 0000:00cf is unknown binary data.
• From offset 0000:00d3 to offset 0000:00de is binary data, which is exactly repeated from offset 0000:00fb to 0000:0107. It starts with the hex numbers 40 6a 40 which seems to be a marker for file seek. It ends with 40 00 04. Inbetween those bytes is data which funktion is still unknown.

• Every object can have a different color in the 8bit-RGB-color-range. E.g. RGB(254,254,254), but most probably it is only black. RGB(0,0,0).

• The size of the canvas is written in pure ansi text. The value could be "ISO A4" or "Letter".

• The hex value 40 seems to be the delimiter between chunks of data of different length. Hex value ff ff ff semms to be a start delimiter and ff ff ff ff semms to be the end delimiter.

Footer

The footer is composed of blocks of data. Each block begins with a 2-byte code indicating the type of data, followed by 1 byte code indicating the datatype and a second 1 byte code indicating how many elements of data are stored.

Header

54 bytes - unknown data

Blocks

The first two bytes of the block provide information on the purpose of the block. The following 2 bytes indicate the type of data and the number of data elements of that type.

Header	Description
00	1 byte of data stored in length byte
01	1-byte data chunks
01	1-byte data chunks
02	2-byte data chunks
03	4-byte data chunks
05	ASCII data chunks

Sample Block Data

Prefix	Type	Length	Data
0x0108	05	13	"Graphtec Craft ROBO" - Optional
0x0208	05	13	"Graphtec Craft ROBO" - Optional
0x0408	05	06	"Letter" - Text Paper Size
0x0508	03	02	56 54 00 00 24 6D 00 00 - Paper size in 1/2540" units (Little Endian) 4-byte width, 4-byte height
0x1B08	01	01	00 - Portrait(0) or Landscape(1)
0x2708	01	01	00
0x1A08	02	01	64 00
0x0908	01	01	00
0x0A08	03	01	00 00 00 00
0x0B08	03	01	00 00 00 00
0x0C08	01	01	00
0x0D08	03	01	00 00 00 00
0x2208	01	01	00
0x2008	01	01	00
0x2108	02	01	00 00
0x2308	02	01	01 00
0x2408	03	01	6F 08 00 00
0x2508	03	01	EA 0A 00 00
0x2608	02	01	01 00
0x0808	02	01	00 00
0x0E08	01	01	00
0x0F08	01	01	01
0x1008	03	01	00 00 00 00
0x1E08	01	01	01
0x1F08	01	01	01
0x1108	01	01	00
0x1C08	03	01	00 00 00 00
0x1D08	03	01	00 00 00 00
0x1408	03	01	00 00 00 00
0x0306	00		00
0x0009	00		09
0x0109	01	01	00
0x0209	01	01	05
0x0309	01	01	05
0x0409	01	01	00
0x0406	00		00
0x000A	00		0A
0x010A	03	01	00 00 00 00
0x020A	00		00
0x000C	00		01
0x010C	03	01	00 00 00 00
0x0506	00		00
0x000E	00		0A
0x010E	01	01	01 - Show Registration Marks
0x020E	02	01	01 00
0x030E	02	01	01 00
0x0A0E	04	01	CD CC CC CC CC 0C 33 40 - Registration Mark Size
0x0B0E	02	01	A8 C6 4B 37 89 41 E0 3F - Registration Mark Thickness
0x0C0E	03	01	66 66 66 66 66 66 29 40 - Origin X
0x0D0E	03	01	52 B8 1E 85 EB 51 24 40 - Origin Y
0x0E0E	03	01	01 00 00 00 00 D0 67 40 - Distance 1-2
0x0F0E	03	01	48 E1 7A 14 AE 87 6E 40 - Distance 1-3
0x110E	01	01	00
0x0606	00		00
0x000F	00		04
0x010F	01	01	00
0x020F	02	01	00 00
0x030F	04	01	66 66 66 66 66 66 29 40 - Grid Spacing
0x040F	01	01	01
0x0010	03	01	00 00 00 00 - End of file?