#!/usr/bin/env python
import png, math, os, functools, operator

def draw_pixel(pixelsss, x, y, rrggbb):
 pixelsss[y][x][0] = int(rrggbb[-6:-4], 16)
 pixelsss[y][x][1] = int(rrggbb[-4:-2], 16)
 pixelsss[y][x][2] = int(rrggbb[-2:  ], 16)
def write_png(path, pixelsss, width, height=None, alpha=False):
 print('> %s' % (path))
 f_out = png.Writer(width=width, height=width if height is None else height, alpha=alpha)
 return f_out.write_array(open(path, 'wb'),
         functools.reduce(operator.iconcat,
         functools.reduce(operator.iconcat, pixelsss, []), []))
def compute_colour(fraction, deg):
 return colours[int((deg + 720 - 360 * fraction + 0.5) / 60) % 6]

n_frame  = 60
w_frame  = 400
h_frame  = 200
radius   = 99
w_frame2 = w_frame // 2
diameter = radius  *  2
colours  = ['ff0000','cc9900','00cc00','3399ff','6666ff','cc33ff']
basename = os.path.splitext(os.path.basename(__file__))[0]
cumulsss = [[[255 for c in range(3)] for x in range(diameter)]
                                     for y in range(diameter)]
for i_frame in range(n_frame + 1): ## 0 = prepare cumulative image
 framesss = [[[255 for c in range(3)] for x in range(w_frame)]
                                      for y in range(h_frame)]
 for y in range(-radius, radius):
  out_y     = y + radius
  out_y_end = (diameter - 1) * i_frame // n_frame
  for x in range(-radius, radius):
   if x * x + y * y < radius * radius:
    out_x = x + radius
    deg   = math.degrees(math.atan2(y, x))
    colour_cumul = compute_colour((y + radius + 1.0) / (diameter - 1), deg)
    colour_disc  = compute_colour(float(i_frame)     / n_frame       , deg)
    if i_frame > 0: draw_pixel(framesss, out_x + 1, out_y, colour_disc )
    else:           draw_pixel(cumulsss, out_x    , out_y, colour_cumul)
  if out_y <= out_y_end: framesss[out_y][w_frame2:w_frame2 + diameter] = cumulsss[out_y]
  for dy in [-1, 0]:
   framesss[out_y_end + dy][1] = framesss[out_y_end + dy][w_frame - 2] = [0,0,0]
  for dy in [-2, 1]:
   framesss[out_y_end + dy][1:w_frame - 1] = [[0,0,0] for i in range(w_frame - 2)]
 if i_frame > 0:
  write_png(r'F:\%s\%02d.png'  % (basename, i_frame), framesss, w_frame, h_frame)
 else:
  write_png(r'F:\%s\00.png' % (basename), cumulsss, diameter, diameter)