#!/usr/bin/env python3
"""Render a GLSL fragment shader to PNG via headless firefox (readPixels -> 2D canvas).
usage: ./render.py shader.frag out.png [time] [width] [height] [mouseX] [mouseY]
"""
import base64, os, subprocess, sys, tempfile
HTML = """
"""
def render(frag_path, out, t=0.0, w=640, h=640, mx=0.5, my=0.5):
src = open(frag_path).read().encode()
b64 = base64.b64encode(src).decode()
html = HTML % dict(w=w, h=h, t=t, mx=mx, my=my,
frag="atob('%s')" % b64)
tmp = tempfile.NamedTemporaryFile("w", suffix=".html", delete=False)
tmp.write(html); tmp.close()
subprocess.run(["firefox", "--headless", "--new-instance", "--profile", "/tmp/ff2",
"--window-size=%d,%d" % (w, h), "--screenshot=" + os.path.abspath(out),
"file://" + tmp.name],
env={**os.environ, "MOZ_NO_REMOTE": "1"},
stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, timeout=120)
os.unlink(tmp.name)
if __name__ == "__main__":
a = sys.argv[1:]
render(a[0], a[1], *(float(x) for x in a[2:]))