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 several sections. A header portion, and several blocks of data. These blocks seem to be related to various configuration information, although the exact purpose is unknown. This is followed by a footer section of static length.

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
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"
0x0208	05	13	"Graphtec Craft ROBO"
0x0408	05	06	"Letter" (or whatever)
0x0508	03	02	56 54 00 00 24 6D 00 00 (unk)
0x1B08	01	01	00
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

Footer

Length	Description
0x48 bytes	unknown
1 byte	use registration mark (bool)
15 bytes	unknown
1 byte	unknown (0x01)
8 bytes	registration mark size
16 bytes	unknown
8 bytes	origin X
4 bytes	unknown
8 bytes	origin Y
3 bytes	unknown
1 byte	show grid (boolean)
8 bytes	Registration Mark distance 1-2
4 bytes	unknown
8 bytes	Registration mark distance 1-3
22 bytes	unknown
1 byte	grid type(0=line, 1=dot)
5 bytes	unknown
8 bytes	grid size
4 bytes	unknown
1 byte	snap to grid(bool)
8 bytes	unknown
<EOF>