shxparser

Pure Python Parser for SHX Hershey font files.

SHX files are an AutoCad format which can encode single line fonts.

This format is used for many CNC and laser operations.

Progress

Things currently parse, text converts to paths. There may be edge cases and bugs within the code.

Encoding

Calling the parser on a SHX file will parse the file. The glyph data is accessed via the ShxFile.glyphs dictionary which stores the particular commands. These positions are stored (or will be) in segments. Each segment is:

• (x0,y0) -- Move to Position.
• ((x0,y0), (x1, y1)) --- Straight Line start->end
• ((x0,y0), (cx, cy), (x1, y1)) --- Arc start->control->end where control is a point on the arc that starts at start and ends at end.

Usage

See test_parser.py for usage:

    def test_parse(self):
        for f in chain(glob("parse/*.SHX"), glob("parse/*.shx")):
            shx = ShxFont(f)
            paths = ShxPath()
            shx.render(paths, "The quick brown fox jumps over the lazy dog", font_size=50)
            draw(paths, 2000, 100, 50, f"{f}.png")

Format

For some format descriptions and explanations see:

• https://help.autodesk.com/view/ACD/2020/ENU/?guid=GUID-0A8E12A1-F4AB-44AD-8A9B-2140E0D5FD23

And:

• https://help.autodesk.com/view/ACD/2020/ENU/?guid=GUID-06832147-16BE-4A66-A6D0-3ADF98DC8228

Primarily the format performs regular (octant direction, distance) and 15 speciality operations.

Regular Command

• Direction, Length pair. If Length is 0 then direction is special command.

Special Commands

• END_OF_SHAPE - Ends the shape.
• PEN_DOWN - Puts the pen down into drawing mode.
• PEN_UP - Puts the pen up into move mode.
• DIVIDE_VECTOR - Applies a vector 1/scale
• MULTIPLY_VECTOR - Applies a vector scale
• PUSH_STACK - Pushes current position to the stack.
• POP_STACK - Pops current position from the stack.
• DRAW_SUBSHAPE - References the glyph data of another glyph.
• XY_DISPLACEMENT - Moves to a long dx, dy position.
• POLY_XY_DISPLACEMENT - Performs a sequence of long dx, dy position changes. 0,0 terminates.
• OCTANT_ARC - Performs an octant_arc operation. Performing an arc across some octants.
• FRACTIONAL_ARC - Performs an octant_arc operation with fractional value offsets.
• BULGE_ARC - Performs bulge arc operations with dx, dy, and bulge.
• POLY_BULGE_ARC - Performs a sequence of bulge arc operations. 0,0 terminates.
• COND_MODE_2 - Performs the next command conditionally, and only if the current mode is vertical.