Speed up svg2png script (#686)

svg2png.py

@@ -2,6 +2,9 @@ from pathlib import Path
 import re
 import shlex
 import subprocess
+import threading
+import queue
+import sys
 
 
 to_p = Path('svg2png')
@@ -11,14 +14,40 @@ for f in to_p.glob('*.png'):
 
 images = [f for f in Path('_build/html/_images/').glob('*.svg')
           if not re.match(r'^seg[0-9A-F]{2}$', f.stem)]
+q = queue.Queue()
 
-for from_ in sorted(images):
-    to_ = to_p / from_.with_suffix('.png').name
-    args = ['inkscape', '-z', '-e', str(to_.absolute()), '-w', '800',
-            '-background', 'white', str(from_.absolute())]
-    print("Running:  {}".format(' '.join(shlex.quote(x) for x in args)))
-    proc = subprocess.run(args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
-    if b'Bitmap saved as' not in proc.stdout:
-        print("Error!")
-        print(proc.stdout)
-        raise ValueError
+
+def worker():
+    while True:
+        item = q.get()
+        if item is None:
+            break
+
+        to = to_p / item.with_suffix('.png').name
+        args = ['inkscape', '-z', '-e', str(to.absolute()), '-w', '800',
+                '-background', 'white', str(item.absolute())]
+        print("Running:  {}".format(' '.join(shlex.quote(x) for x in args)))
+        proc = subprocess.run(args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+        if b'Bitmap saved as' not in proc.stdout:
+            print("Error!")
+            print(proc.stdout)
+            sys.exit(1)
+
+        q.task_done()
+
+NUM_THREADS = 8
+threads = []
+for i in range(NUM_THREADS):
+    t = threading.Thread(target=worker)
+    t.start()
+    threads.append(t)
+
+for img in sorted(images):
+    q.put(img)
+
+q.join()
+
+for i in range(NUM_THREADS):
+    q.put(None)
+for t in threads:
+    t.join()