#!/usr/bin/env python
PATH_INKSCAPE = r'C:\APP\inkscape122\bin\inkscape.exe'
DIR_OUT       = r'F:\gif'
WIDTH_OUT     = 512
SCALE         = 100
N_FRAME       = 10
FORMAT_SVG    = '''\
<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="-10 -290 300 300">
 <circle r="999" fill="#fff"/>
 <g fill="none" stroke="#000">
  <path id="axis" d="M -9,0 H 288 m -7,-4 l 7,4 l -7,4"/>
  <use xlink:href="#axis" transform="matrix(0,-1 1,0 0,0)"/>
  <path d="{out_d}" fill="#fc0"/>
  <path d="M 5,-2000 Q 0,-360 50,-200 C 70,-114 114,-70 200,-50 Q 360,0 2000,-5" fill="#fff"/>
 </g>
</svg>
'''
import re, math, subprocess
def system(command, cwd='./', is_verbose=False):
 if is_verbose: print('%s %s' % (cwd, command))
 return subprocess.Popen(command, stdout=subprocess.PIPE, cwd=cwd,
                         shell=True).communicate()[0].decode('utf-8')
def fmt(string): ## string.format(**vars()) using tags {expression!format} by CMG Lee
 def f(tag): i_sep = tag.rfind('!'); return (re.sub('\.0$', '', str(eval(tag[1:-1])))
  if (i_sep < 0) else ('{:%s}' % tag[i_sep + 1:-1]).format(eval(tag[1:i_sep])))
 return (re.sub(r'(?<!{){[^{}]+}', lambda m:f(m.group()), string)
         .replace('{{', '{').replace('}}', '}'))

path_prefix = r'%s\%s' % (DIR_OUT, os.path.basename(os.path.splitext(__file__)[0]))
for n in range(N_FRAME):
 a        = math.exp(n / 5.0 - 1)
 b        = math.exp(n / 5.0 - 0.8)
 out_d    = 'M %.0f,%.0f L 0,0 L %.0f,%.0f' % (SCALE * a, -SCALE / a,
                                               SCALE * b, -SCALE / b)
 path_svg = '%s%02d.svg' % (path_prefix, n)
 path_png = '%s%02d.png' % (path_prefix, n)
 with open(path_svg, 'w') as f: f.write(fmt(FORMAT_SVG))
 system('%s -o %s -w %d %s' % (PATH_INKSCAPE, path_png, WIDTH_OUT, path_svg), is_verbose=True)
for n in range(1, N_FRAME - 1):
 path_svg = '%s%02d.svg' % (path_prefix, n)
 path_png = '%s%02d.png' % (path_prefix, N_FRAME * 2 - 2 - n)
 system('%s -o %s -w %d %s' % (PATH_INKSCAPE, path_png, WIDTH_OUT, path_svg), is_verbose=True)
## Then drag PNGs into http://ezgif.com/maker and then Optimize at Compression
##  level: 200, Eliminate local color tables, Reduce the number of colors to 4