bedstead/editor

#!/usr/bin/env python3

# Interactive glyph editor for Bedstead.
#
# This program was written by Simon Tatham in 2013 and updated by Ben
# Harris in 2024.
#
# Simon Tatham and Ben Harris make this program available under the
# CC0 Public Domain Dedication.

'''Interactive glyph editor for Bedstead.

Uses Python/Tk to display a window with a pixel grid on the left side,
where the user can click or drag to toggle pixels on and off, and on
the right, shows the output of the Bedstead smoothing algorithm
applied to that grid of pixels.

This is done by running the `bedstead` executable itself to compute
the smoothed outline, so a copy of that executable is required to use
this editor.

'''

import argparse
import os
import re
import sys
import string
import subprocess
import tkinter

gutter = 20
pixel = 32
XSIZE, YSIZE = 5, 9
LEFT, TOP = 100, 700 # for transforming coordinates returned from bedstead

class EditorGui:
    def __init__(self, bedstead):
        self.bedstead = bedstead

        self.tkroot = tkinter.Tk()

        self.canvas = tkinter.Canvas(self.tkroot,
                                     width=2 * (XSIZE*pixel) + 3*gutter,
                                     height=YSIZE*pixel + 2*gutter,
                                     bg='white')
        self.bitmap = [0] * YSIZE
        self.oldbitmap = self.bitmap[:]
        self.pixels = [[None]*XSIZE for y in range(YSIZE)]
        self.polygons = []

        for x in range(XSIZE+1):
            self.canvas.create_line(gutter + x*pixel, gutter,
                                    gutter + x*pixel, gutter + YSIZE*pixel)
        for y in range(YSIZE+1):
            self.canvas.create_line(gutter, gutter + y*pixel,
                                    gutter + XSIZE*pixel, gutter + y*pixel)

        self.canvas.bind("<Button-1>", self.click)
        self.canvas.bind("<B1-Motion>", self.drag)
        self.canvas.bind("<Button-2>", self.paste)
        self.tkroot.bind("<Key>", self.key)
        self.canvas.pack()

    def getpixel(self, x, y):
        assert x >= 0 and x < XSIZE and y >= 0 and y < YSIZE
        bit = 1 << (XSIZE-1 - x)
        return self.bitmap[y] & bit

    def setpixel(self, x, y, state):
        assert x >= 0 and x < XSIZE and y >= 0 and y < YSIZE
        bit = 1 << (XSIZE-1 - x)
        if state and not (self.bitmap[y] & bit):
            self.bitmap[y] |= bit
            self.pixels[y][x] = self.canvas.create_rectangle(
                gutter + x*pixel, gutter + y*pixel,
                gutter + (x+1)*pixel, gutter + (y+1)*pixel,
                fill='black')
        elif not state and (self.bitmap[y] & bit):
            self.bitmap[y] &= ~bit
            self.canvas.delete(self.pixels[y][x])
            self.pixels[y][x] = None

    def regenerate(self):
        if self.oldbitmap == self.bitmap:
            return

        self.oldbitmap = self.bitmap[:]

        for pg in self.polygons:
            self.canvas.delete(pg)
        self.polygons = []

        data = subprocess.check_output(
            [self.bedstead] + list(map(str, self.bitmap)),
            universal_newlines=True)
        class CharstringInterpreter:
            def __init__(self):
                self.paths = []
                self.path = None
                self.stack = []
                self.cursor = [0, 0]
                self.skip = False
            def rmoveto(self):
                self.path = []
                self.paths.append(self.path)
                self.rlineto()
            def rlineto(self):
                while len(self.stack) >= 2:
                    self.cursor[0] += self.stack[0]
                    self.cursor[1] += self.stack[1]
                    self.stack = self.stack[2:]
                    self.path.append(self.cursor[:])
            def op(self, word):
                try:
                    if not self.skip:
                        self.stack.append(float(word))
                    self.skip = False
                except:
                    if word == "rmoveto": self.rmoveto()
                    elif word == "rlineto": self.rlineto()
                    elif word in ("hstem", "vstem"): self.stack = []
                    elif word in ("cntrmask", "hintmask"): self.skip = True
                    elif word == "endchar": pass
                    else:
                        print("unknown charstring component " + repr(word))
        interp = CharstringInterpreter()
        data = re.sub(r"<!--(?:[^-]|-[^-])*-->", "", data)
        for word in data.split():
            interp.op(word)
        paths = [[[int((float(x)-LEFT)*pixel*0.01 + 2*gutter + XSIZE*pixel),
                   int((TOP - float(y))*pixel*0.01 + gutter)]
                  for x, y in path] for path in interp.paths]

        # The output from 'bedstead' will be a set of disjoint paths,
        # in the Postscript style (going one way around the outside of
        # filled areas, and the other way around internal holes in
        # those areas). Python/Tk doesn't know how to fill an
        # arbitrary path in that representation, so instead we must
        # convert into a set of individual Tk polygons (convex shapes
        # with a single closed outline) and display them in the right
        # order with the right colour.
        #
        # A neat way to arrange this is to compute the area enclosed
        # by each polygon, essentially by integration: for each line
        # segment (x0,y0)-(x1,y1), sum the y difference (y1-y0) times
        # the average x value, which gives the area between that line
        # segment and the corresponding segment of the x-axis. After
        # we go all the way round an outline in this way, we'll have
        # precisely the area enclosed by the outline, no matter how
        # many times it doubles back on itself (because every piece of
        # x-axis has been cancelled out by an outline going back the
        # other way). Furthermore, the sign of the integral we've
        # computed tells us whether the outline goes one way or the
        # other around the area.
        #
        # So then we sort our paths into descending order of the
        # absolute value of its computed area (guaranteeing that any
        # path contained inside another appears after it, since it
        # must enclose a strictly smaller area) and fill each one with
        # a colour based on the area's sign.
        #
        # This strategy depends critically on 'bedstead' having given
        # us sensible paths in the first place: it wouldn't handle an
        # _arbitrary_ PostScript path, with loops allowed to overlap
        # and intersect rather than being neatly nested.
        pathswithmetadata = []
        for path in paths:
            area = 0
            for i in range(len(path)):
                x0, y0 = path[i-1]
                x1, y1 = path[i]
                area += (y1-y0) * (x0+x1)/2
            pathswithmetadata.append([abs(area),
                                     ('black' if area<0 else 'white'),
                                      path])
        pathswithmetadata.sort(reverse=True)

        for _, colour, path in pathswithmetadata:
            if len(path) > 1:
                args = sum(path, []) # x,y,x,y,...,x.y
                pg = self.canvas.create_polygon(*args, fill=colour)
                self.polygons.append(pg)

    def click(self, event):
        for dragstartx in gutter, 2*gutter + XSIZE*pixel:
            x = (event.x - dragstartx) // pixel
            y = (event.y - gutter) // pixel
            if x >= 0 and x < XSIZE and y >= 0 and y < YSIZE:
                self.dragstartx = dragstartx
                self.dragstate = not self.getpixel(x,y)
                self.setpixel(x, y, self.dragstate)
                self.regenerate()
                break

    def paste(self, event):
        s = self.tkroot.selection_get()
        pat = re.compile("[0-7]+")
        bitmap = []
        for i in range(YSIZE):
            m = pat.search(s)
            if m is None:
                print("Unable to interpret selection data {!r} as a "
                      "Bedstead glyph description".format(s))
                return
            bitmap.append(int(m.group(0), 8) & ((1 << XSIZE) - 1))
            s = s[m.end(0):]
        for y in range(YSIZE):
            for x in range(XSIZE):
                self.setpixel(x, y, 1 & (bitmap[y] >> (XSIZE-1 - x)))
        self.regenerate()

    def drag(self, event):
        x = (event.x - self.dragstartx) // pixel
        y = (event.y - gutter) // pixel
        if 0 <= x < XSIZE and 0 <= y < YSIZE:
            self.setpixel(x, y, self.dragstate)
            self.regenerate()

    def key(self, event):
        if event.char in (' '):
            bm = "".join(map(lambda n: "\\%02o" % n, self.bitmap))
            print(' {"%s", U() },' % bm)
        elif event.char in ('c','C'):
            for y in range(YSIZE):
                for x in range(XSIZE):
                    self.setpixel(x, y, 0)
            self.regenerate()
        elif event.char in ('q','Q','\x11'):
            sys.exit(0)

    def run(self):
        tkinter.mainloop()

def main():
    # By default, assume that the user ran 'make' in the bedstead
    # source directory, so that the 'bedstead' executable is alongside
    # the binary.
    default_executable_path = os.path.join(
        os.path.dirname(os.path.abspath(__file__)), "bedstead")

    parser = argparse.ArgumentParser(
        description=__doc__,
        formatter_class=argparse.RawDescriptionHelpFormatter)
    parser.add_argument("--bedstead", default=default_executable_path,
                        help="Location of the 'bedstead' executable.")
    args = parser.parse_args()

    editor = EditorGui(args.bedstead)
    editor.run()

if __name__ == '__main__':
    main()