From 9e9e136f542aeaf5afb5a30fa08a1a70733e74d3 Mon Sep 17 00:00:00 2001
From: Andrew Murray <radarhere@users.noreply.github.com>
Date: Tue, 7 Apr 2020 21:42:23 +1000
Subject: [PATCH] Do not save two temporary files for the same size

---
 src/PIL/IcnsImagePlugin.py | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/PIL/IcnsImagePlugin.py b/src/PIL/IcnsImagePlugin.py
index 98603e2f9..cf9b5dcf5 100644
--- a/src/PIL/IcnsImagePlugin.py
+++ b/src/PIL/IcnsImagePlugin.py
@@ -325,10 +325,12 @@ def _save(im, fp, filename):
     file_size = 0
     entries = []
     provided_images = {im.width: im for im in im.encoderinfo.get("append_images", [])}
-    for index, s in enumerate(sizes):
-        temp = io.BytesIO()
+    temp_sizes = {s: io.BytesIO() for s in set(sizes)}
+    for s, temp in temp_sizes.items():
         nb = provided_images[s] if s in provided_images else im.resize((s, s))
         nb.save(temp, "png")
+    for index, s in enumerate(sizes):
+        temp = temp_sizes[s]
         file_size += len(temp.getvalue())
         entries.append(
             {"type": size_str[index], "size": len(temp.getvalue()), "stream": temp}
@@ -343,14 +345,14 @@ def _save(im, fp, filename):
     fp.write(struct.pack("<i", _to_int(TOC))[::-1])
     fp.write(struct.pack("<i", toc_size)[::-1])
     for e in entries:
-        fp.write(struct.pack("<i", _to_int(e.get("type")))[::-1])
-        fp.write(struct.pack("<i", HEADERSIZE + e.get("size"))[::-1])
+        fp.write(struct.pack("<i", _to_int(e["type"]))[::-1])
+        fp.write(struct.pack("<i", HEADERSIZE + e["size"])[::-1])
 
     # Data
     for index, e in enumerate(entries):
-        fp.write(struct.pack("<i", _to_int(e.get("type")))[::-1])
-        fp.write(struct.pack("<i", HEADERSIZE + e.get("size"))[::-1])
-        fp.write(e.get("stream").getvalue())
+        fp.write(struct.pack("<i", _to_int(e["type"]))[::-1])
+        fp.write(struct.pack("<i", HEADERSIZE + e["size"])[::-1])
+        fp.write(e["stream"].getvalue())
 
     fp.flush()