first pass at SVG font extractor for moving into fontforge

roms/font_extract.py

@@ -0,0 +1,68 @@
+#!/usr/bin/python3
+import sys
+import math
+import cairo
+import struct
+
+alpha_ft_start = 0x2569
+point_ft_start = 0x3153
+
+f = open("ROM.bin","rb")
+data = f.read()
+
+
+def eot(ft, off):
+    "Returns true if the offset is at the end of the table."
+    # Presumes that every table terminates in 0xff
+    return data[ft + off*2] == 0xff
+
+def get_char(ft,off):
+    achar = chr(off+0x20)
+    o1 = ft + (off*2)
+    o2 = (data[o1+1]*256) + data[o1]
+    o3 = o2
+    while data[o3] != 0xff:
+        o3 += 1
+    return data[o2:o3]    
+
+def unpack_byte(b):
+    "convert two 4-bit signed packed numbers to a tuple"
+    def sign4b(x):
+        # not... quite two's complement
+        if x > 8:
+            return x - 16
+        return x
+    return (sign4b(b>>4), sign4b(b % 16))
+
+def unpack_coords(b,scale=100,xoff=0,yoff=0):
+    "convert two 4-bit signed packed numbers to cairo coordinates"
+    (x,y) = unpack_byte(b)
+    return (x*scale, (8 - y)*scale + yoff)
+
+def build_char_file(path, ft, offset):
+    surf = cairo.SVGSurface(path, 1000, 1000)
+    c = cairo.Context(surf)
+    d = list(get_char(ft, offset))
+    c.set_source_rgb(0, 0, 0)
+    c.set_line_width(20)
+    c.set_line_cap(cairo.LINE_CAP_ROUND)
+    while d:
+        cmd = d.pop(0)
+        cn, ca = cmd >> 4, cmd % 16
+        for _ in range(ca):
+            (x,y) = unpack_coords(d.pop(0))
+            if cn == 0:
+                c.move_to(x,y)
+            elif cn == 2:
+                c.line_to(x,y)
+    c.stroke()
+    surf.finish()
+
+def dump_font(path_base, ft, charoff):
+    off = 0
+    while not eot(ft, off):
+        build_char_file("{}_{:2x}.svg".format(path_base,charoff+off),ft,off)
+        off += 1
+
+dump_font("alpha",alpha_ft_start,0x20)
+