Remake of baoilleach/bresenham.py for Python 3

pylines.py

DEBUG = print if 0 else lambda *_:()

from math import cos, sin, pi

ASPECT = 15./10.

def bresenham_line(start, end):
    symbols = getsymbols(start, end)
    (x1, y1), (x2, y2) = start, end
    steep = False
    coords = []
    dx = abs(x2 - x1)
    dy = abs(y2 - y1)
    sx = 1 if x2 > x1 else -1
    sy = 1 if y2 > y1 else -1
    if dy > dx:
        steep = True
        x1,y1 = y1,x1
        dx,dy = dy,dx
        sx,sy = sy,sx
    d = (2 * dy) - dx
    syms = []
    delta = 0
    for i in range(dx):
        syms.append(symbols[d>=0])
        delta = 0
        if syms[-1] in "/\\":
            delta = getdelta(start,end)
        if steep:
            coords.append((y1,x1 + delta))
        else:
            coords.append((x1,y1 + delta))
        while d >= 0:
            y1 = y1 + sy
            d = d - (2 * dx)
        x1 = x1 + sx
        d = d + (2 * dy)
    syms.append(symbols[d>=0])
    delta = 0
    if syms[-1] in "/\\":
        delta = getdelta(start,end)
    coords.append((x2,y2 + delta))
    if len(coords) > 1:
        if syms[0] == "|":
            if coords[0][1] < coords[1][1]:
                syms, coords = syms[1:], coords[1:]
        if syms[-1] == "|":
            DEBUG("HAPPENED!")
            if coords[-1][1] < coords[-2][1]:
                syms, coords = syms[:-1], coords[:-1]
    return coords, syms


class Screen(object):
    def __init__(self, width, height):
        self.w = width
        self.h = height
        self.buf = [[" "]*self.w for x in range(self.h)]

    def __str__(self):
        ans=["-----START"]
        for x in self.buf:
            ans.append("".join(x))
        ans.append("-----END")
        return "\n".join(ans)

    def line(self, start, end):
        coords, syms = bresenham_line( start, end )
        DEBUG(coords, syms)
        for (a, b), sym in zip(coords, syms):
            if 0<=b<self.h and 0<=a<self.w:
                self.buf[b][a] = sym

    def text(self, text, pos):
        start = pos[0]
        for i, x in enumerate(text):
            if 0 <= pos[1] < self.h and 0 <= start+i < self.w:
                self.buf[pos[1]][start + i] = x


def getsymbols(start ,end):
    """
    >>> getsymbols((9, 4), (19, 5))
    ['_', '\\\\']
    >>> getsymbols((9, 4), (0, 3))
    ['_', '\\\\']
    >>> getsymbols((9, 4), (15, 8))
    ['_', '\\\\']
    >>> getsymbols((9, 4), (7, 9))
    ['|', '/']
    >>> getsymbols((9, 4), (3, 0))
    ['_', '\\\\']
    >>> getsymbols((9, 4), (1, 7))
    ['_', '/']
    >>> getsymbols((9, 4), (12, 9))
    ['|', '\\\\']
    """
    if end[0] < start[0]:
        start, end = end, start
    if end[0] == start[0]:
        slope = 1e99
    else:
        slope = (end[1] - start[1]) / float((end[0] - start[0]))
    if slope > 0:
        if slope > 1.0:
            ans = ["|", '\\']
        else:
            ans = ["_", '\\']
    else:
        if slope > -1.0:
            ans = ["_", "/"]
        else:
            ans = ["|", "/"]
    return ans


def getdelta(start, end):
    """
    >>> getdelta((9, 4), (18, 7))
    1
    >>> getdelta((9, 4), (12, 9))
    0
    >>> getdelta((9, 4), (7, 9))
    0
    """
    return end[1] > start[1] and abs((end[1] - start[1]) / (end[0] - start[0])) <= 1.0


def mytest():
    screen = Screen(10,10)
    screen.buf[0] = list("0123456789")
    for i in range(10):
        screen.buf[i][0] = str(i)
    screen.line( (2,3), (3,5))
    print(screen)

    DEBUG(getsymbols((25,14), (17,11)))


if __name__ == "__main__":
    mytest()
    star = True
    square = True
    normal = True

    if star:
        w, h = 170 ,48
        w, h = 78, 48
        screen = Screen(w, h)
        start = 0
        x, y = round(w/2.)-1, round(h/2.)-1
        oldx, oldy = w-1, y
        for ang in range(start, 360 + start + 10, 10):
            x2 = round(x + w/2*cos(ang*pi/180))
            y2 = round(y + h/2*sin(ang*pi/180))
            screen.line((x, y), (x2, y2))
            screen.line((oldx, oldy), (x2, y2))
            oldx,oldy=x2,y2
        print(screen)

    if square:
        w = 30
        h = round(w/ASPECT)
        screen = Screen(w, h)
        points = [(0, 0), (w-1, 0), (w-1, h-1), (0, h-1), (0, 0)]
        for src, dest in zip(points, points[1:]):
            screen.line(src, dest)
        start = 30
        x, y = round(w/2.)-1, round(h/2.)-1
        for i, size in enumerate([w/2., w/2. - 4]):
            x2, y2 = round(x+size*cos(start*pi/180.)),round(y+(size/ASPECT)*sin(start*pi/180.))
            oldx, oldy = x2, y2
            for ang in range(start, 360 + start + 60, 60):
                x2, y2 = round(x+size*cos(ang*pi/180.)),round(y+(size/ASPECT)*sin(ang*pi/180.))
                if i==0 or (i==1 and (ang/60)%2==0 ):
                    screen.line((oldx,oldy),(x2,y2))
                oldx,oldy=x2,y2
        print(screen)

    if normal:
        output = open('test.bbl','r').read()
        DEBUG(output)

        w, h = 76, 30
        scale = 0.3
        screen = Screen(w, h)
        for line in output.split("\n"):
            DEBUG(line)
            fields = line.split()
            if line.startswith("NewCanvas"):
                vals = [float(x) for x in fields[1:3]]
                cw, ch = vals[0], vals[1]/ASPECT
                sx, sy = w/cw, h/ch
                scale = min(sx, sy)
            elif line.startswith("DrawLine"):
                tmp = [fields[i] for i in [1,2,4,5]]
                vals = [float(x)*scale for x in tmp]
                screen.line((round(vals[0]), round(vals[1]/ASPECT)),
                            (round(vals[2]), round(vals[3]/ASPECT)))
            elif line.startswith("DrawText"):
                vals = [float(x)*scale for x in fields[1:3]]
                screen.text(fields[3][1:-1],
                            (round(vals[0]), round(vals[1]/ASPECT)))

        print(screen)

test.bbl

NewCanvas 149.3 140.0
SetPenColor 0.0 0.0 0.0 1.0 (rgba)
DrawLine 109.3 100.0 to 74.6 80.0
SetPenColor 0.0 0.0 0.0 1.0 (rgba)
DrawLine 71.6 80.0 to 71.6 53.0
DrawLine 77.6 80.0 to 77.6 53.0
SetPenColor 0.0 0.0 0.0 1.0 (rgba)
DrawLine 74.6 80.0 to 51.3 93.5
SetPenColor 0.4 0.4 0.4 1.0 (rgba)
SetPenColor 0.4 0.4 0.4 1.0 (rgba)
SetPenColor 1.0 0.1 0.1 1.0 (rgba)
SetFontSize 16
SetFontSize 16
SetFontSize 16
DrawText 74.6 40.0 "O"
SetPenColor 0.1 0.9 0.1 1.0 (rgba)
SetFontSize 16
SetFontSize 16
SetFontSize 16
SetFontSize 16
DrawText 40.0 100.0 "Cl"

There are still plenty of opportunities for simplification or condensing, such as removing unnecessary float(...) calls or combining lines, e.g. scale = min(w/cw, h/ch)

The top line sets whether debug info is printed. DEBUG(...) can contain any number of arguments which are then passed to print when this line has a true condition. If the condition is false, a lambda takes the arguments and does nothing with them. Presto change-o!