A set of python scripts to show the animation of the problem POJ1070: Deformed Wheel.

gdebugpoj1070.py

import pygame as pg
import sys
from pygame.locals import *
import subprocess as sb

W, H = 800, 600
x0, y0 = 400, 400
BgColor = (0xff, 0xff, 0xff, 0xff)
LineColor = (0, 0, 0, 0xff)
SCROLL_UP, SCROLL_DOWN = 4, 5
k = 3.
inputfile='map-poj1070-0002'

def onexit():
    proc.kill()

sys.exitfunc = onexit

def init():
    global screen, proc, font
    pg.display.init()
    pg.font.init()
    screen = pg.display.set_mode((W, H), 0, 32)
    proc = sb.Popen(['./a', inputfile], stdout=sb.PIPE, stderr=sb.PIPE, stdin=sb.PIPE)
    font = pg.font.SysFont('monospace', 16)

lines = []
data = []
def fetch():
    global waiting
    while 1:
        line = proc.stdout.readline()
        if not line:
            # eof
            return
        line = line.rstrip()
        if line.startswith(':'):
            line = line[1:]
            if line == 'stroke':
                waiting = 1
                return
            lines.append(line)
        else:
            print 'client: ', line

def send():
    try:
        proc.stdin.write(':\n')
        proc.stdin.flush()
    except IOError as e:
        sys.stderr.write(proc.stderr.read())
        print e

def tfp((x, y)):
    return (int(k*x + x0), int(-y*k + y0))

def rtfp((x, y)):
    return ((x - x0 - 0.)/k, (-y + y0 - 0.)/k)

def transform(ps):
    return [tfp((x, y)) for x, y in ps]

cnt = 0
def draw():
    global cnt, data, lines
    cnt += 1
    print 'draw', cnt
    data = lines
    lines = []
    redraw()

def redraw():
    global data
    if not data: return
    databk = data[:]
    n = int(data.pop(0))
    ps = transform([map(float, data.pop(0).split()) for i in xrange(n)])
    g = tfp(map(float, data.pop(0).split()))
    m = int(data.pop(0))
    ps1 = transform([map(float, data.pop(0).split()) for i in xrange(m)])

    screen.fill(BgColor)
    pg.draw.polygon(screen, LineColor, ps, 1)
    for i, p in enumerate(ps):
        pg.draw.circle(screen, (255*i/n, 0, 0, 0xff), p, 4)
    pg.draw.lines(screen, LineColor, 0, ps1, 1)
    pg.draw.circle(screen, (0, 0, 0xff, 0xff), g, 4)

    # draw the coordinate
    pg.draw.circle(screen, (0, 0xff, 0, 0xff), tfp((0, 0)), 4)

    screen.blit(txt, (0, 0))

    pg.display.flip()
    data = databk

init()
waiting = 0
pg.key.set_repeat(500, 50)
txt = pg.Surface((1, 1))
mpos = None
dx, dy = 0, 0
while 1:
    for e in pg.event.get():
        if e.type == QUIT:
            exit(0)
        if e.type == KEYDOWN:
            if e.key == K_RETURN:
                if waiting:
                    send()
                    waiting = 0
                else:
                    print 'not waiting, ignored'
            elif e.key == K_SPACE:
                k = 3
                x0 = 400
                y0 = 400
                redraw()
            if e.key == K_q:
                exit(0)
        if e.type == MOUSEBUTTONDOWN:
            if e.button in (SCROLL_UP, SCROLL_DOWN):
                x, y = rtfp(e.pos)
                dk = 0.1
                if e.button == SCROLL_UP:
                    k *= (1+dk)
                if e.button == SCROLL_DOWN:
                    k /= (1+dk)
                x0 = e.pos[0] - k * x
                y0 = e.pos[1] + k * y
                redraw()
            if e.button == 1:
                txt = font.render("(%.1f, %.1f)" % rtfp(e.pos), 1, (0, 0, 0, 0xff), BgColor)
                redraw()

        elif e.type == MOUSEMOTION:
            if e.buttons[0]:
                dx += e.rel[0]
                dy += e.rel[1]
                if dx*dx+dy*dy > 40:
                    x0, y0 = x0 + dx, y0 + dy
                    dx, dy = 0, 0
                    redraw()
    if not waiting:
        fetch()
    if lines:
        draw()

genpoj1070.py

import pygame as pg
import sys, os
from pygame.locals import *
import subprocess as sb

W, H = 1200, 800
x0, y0 = 400, 400
BgColor = (0xff, 0xff, 0xff, 0xff)
LineColor = (0, 0, 0, 0xff)
SCROLL_UP, SCROLL_DOWN = 4, 5
k = 3.
poly = []
gra = None
hill = []
pbuf = []

def init():
    global screen, proc, font
    pg.display.init()
    pg.font.init()
    screen = pg.display.set_mode((W, H), 0, 32)
    font = pg.font.SysFont('monospace', 12)

def tfp((x, y)):
    return (int(k*x + x0), int(-y*k + y0))

def rtfp((x, y)):
    return ((x - x0 - 0.)/k, (-y + y0 - 0.)/k)

def transform(ps):
    return [tfp((x, y)) for x, y in ps]

def inform(msg):
    h = 0
    txt.fill((0, 0, 0, 0))
    for line in msg.split('\n'):
        txtline = font.render(line, 1, LineColor)
        txt.blit(txtline, (5, h))
        h += font.size(line)[1]
    redraw()
    print msg

def add_point(p):
    pbuf.append(p)
    inform("add point at (%.2f, %.2f)" % p)

def collect_poly():
    while len(pbuf) > 1:
        poly.append(pbuf.pop(0))
    global gra
    gra = pbuf.pop(0)
    inform("polygon collected\ngravity center collected\n")

def collect_hill():
    while len(pbuf):
        hill.append(pbuf.pop(0))

def dist(a, b):
    return ((a[0] - b[0])**2 + (a[1] - b[1])**2)**0.5
def collect_save():
    prefix = 'map-poj1070-%04d'
    for i in xrange(1000):
        fn = prefix % i
        if not os.path.exists(fn):
            pg.image.save(screen, fn + '.png')
            with open(fn, 'w') as fout:
                print >> fout, 1
                print >> fout, len(poly)
                print >> fout, '\n'.join('%.2f %.2f' % p for p in poly)
                print >> fout, '%.2f %.2f' % gra

                endp = None
                for p in poly:
                    if endp is None or dist(endp, hill[0]) > dist(p, hill[0]):
                        endp = p
                hill[0] = endp
                x0, y0 = endp
                for x, y in hill[1:]:
                    k = (y - y0)/(x - x0 - 0.)
                    if k < -1e-8:
                        print 'WARNING: DATA INVALID. k = %s => k = 0, expected k >= 0' % (k,)
                        k = 0
                    l = ((y-y0)**2+(x-x0)**2)**0.5
                    print >> fout, '%.2f %.2f' % (l, k)
                    x0, y0 = x, y
                print >> fout, '%.2f %.2f' % endp
            inform("saved as %s and %s.png" % (fn, fn))
            break
    else:
        inform("can not save, too many files")

def redraw():
    screen.fill(BgColor)
    for p in pbuf:
        pg.draw.circle(screen, (0xff, 0, 0, 0xff), tfp(p), 3)
    if poly:
        # draw poly
        pg.draw.polygon(screen, LineColor, transform(poly), 1)
        pg.draw.circle(screen, (0, 0, 0xff, 0xff), tfp(gra), 4)
    if hill:
        pg.draw.lines(screen, LineColor, 0, transform(hill), 1)

    pg.draw.circle(screen, (0, 0xff, 0, 0xff), tfp((0, 0)), 4)
    pg.draw.circle(screen, (0, 0, 0, 0xff), tfp((100, 100)), 4)

    screen.blit(txt, (0, 0))
    pg.display.flip()

init()
# pg.key.set_repeat(500, 50)
txt = pg.Surface((500, 300)).convert_alpha()
mpos = None
dx, dy = 0, 0
helpMsg = """Welcome the the data maker of poj1070: Deformed Wheel
Use left mouse button to add new point
Use backspace to undo
Use mouse scroll to zoom
Drag with right mouse button to navigate
Use spacebar to reset the view
Use enter to goto next state, note this can not be undo
Press F1 to show this message
"""

inform(helpMsg)
collectors = [collect_poly, collect_hill, collect_save]
timer = pg.time.Clock()
while 1:
    for e in pg.event.get():
        if e.type == QUIT:
            exit(0)
        if e.type == KEYDOWN:
            if e.key == K_SPACE:
                # reset view
                k = 3
                x0 = 400
                y0 = 400
                redraw()
            if e.key == K_q:
                exit(0)
            if e.key == K_F1:
                inform(helpMsg)
            if e.key == K_RETURN:
                collector = collectors.pop(0)
                collector()
            if e.key == K_BACKSPACE:
                if pbuf:
                    pbuf.pop()
                    redraw()
        if e.type == MOUSEBUTTONDOWN:
            if e.button in (SCROLL_UP, SCROLL_DOWN):
                # zoom
                x, y = rtfp(e.pos)
                dk = 0.1
                if e.button == SCROLL_UP:
                    k *= (1+dk)
                if e.button == SCROLL_DOWN:
                    k /= (1+dk)
                x0 = e.pos[0] - k * x
                y0 = e.pos[1] + k * y
                redraw()
            if e.button == 1:
                add_point(rtfp(e.pos))
                redraw()

        elif e.type == MOUSEMOTION:
            if e.buttons[2]:
                dx += e.rel[0]
                dy += e.rel[1]
                if dx*dx+dy*dy > 40:
                    x0, y0 = x0 + dx, y0 + dy
                    dx, dy = 0, 0
                    redraw()
    redraw()
    timer.tick(30)