Graphic Mini-language Parser

This is a command-line interface which uses monadic parsing to produce commands for a drawing-system from opcode strings.

Integers

Integers in the opcode string are encoded according to the following scheme. Valid integers are between [-8192, +8191].

To encode a raw decimal:

• Add 8192 to the decimal.
• Convert decimal to 16-bit binary. Since valid integers are 14-bit, 2 most significant bits will be cleared:

00HHHHHH HLLLLLLL

• Pack bytes such that the most significant bit of each is cleared:

0HHHHHHH 0LLLLLLL

• Finally, convert resulting binary numeral into hexadecimal.

Sample Values

Unencoded (decimal)	Encoded (hex)
0	4000
8191	7F7F
2048	5000
-4096	2000

Commands

Clear

Command	Opcode	Parameters	Output
CLR	F0	none	CLR; \n

This command resets pen position and color.

Pen Up/Pen Down

Command	Opcode	Parameters	Output
PEN	80	0 = pen up, any other integer value = pen down	PEN UP; \n or PEN DOWN; \n

When pen is up, no mark is made.

Color

Command	Opcode	Parameters	Output
CO	A0	R, G, B, and Alpha. (0...255)	CO {R} {G} {B} {A}

Move

Command	Opcode	Parameters	Output
MV	C0	x0 y0 [x1 y1 ... xn yn]	If pen is up, move to final position. Otherwise: MV (x0, y0) [... (xn, yn)];\n

While the encoded commands will give coordinates relative to current pen position, output should display absolute coordinates.

If command takes pen outside of (-8192, -8192) ... (8191, 8191) then pen should move until it reaches the boundary, lift, and then lower once it re-enters the canvas.

Examples

Blue Square

Input:

F0A040004000417F417FC04000400090400047684F5057384000804001C05F204000400001400140400040007E405B2C4000804000

Output:

CLR;
CO 0 0 255 255;
MV (0, 0);
PEN DOWN;
MV (4000, 0) (4000, -8000) (-4000, -8000) (-4000, 0) (-500, 0);
PEN UP;

Clipping on Canvas Border

F0A0417F41004000417FC067086708804001C067082C3C18782C3C804000

Output:

CLR;
CO 255 128 0 255;
MV (5000, 5000);
PEN DOWN;
MV (8191, 3405);
PEN UP;
MV (8191, 1596);
PEN DOWN;
MV (5000, 0);
PEN UP;