From 361f579579ca9cfed40a9bb4fc322e0ea99d60e4 Mon Sep 17 00:00:00 2001
From: Andrew Murray <radarhere@gmail.com>
Date: Sun, 15 Jan 2017 17:36:59 +1100
Subject: [PATCH] Moved iCCP chunk before PLTE chunk when saving as PNG

---
 PIL/PngImagePlugin.py  | 24 ++++++++++++------------
 Tests/test_file_png.py | 19 +++++++++++++++++++
 2 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/PIL/PngImagePlugin.py b/PIL/PngImagePlugin.py
index dca8a456e..486162a38 100644
--- a/PIL/PngImagePlugin.py
+++ b/PIL/PngImagePlugin.py
@@ -715,6 +715,18 @@ def _save(im, fp, filename, chunk=putchunk, check=0):
           b'\0',                                # 11: filter category
           b'\0')                                # 12: interlace flag
 
+    icc = im.encoderinfo.get("icc_profile", im.info.get("icc_profile"))
+    if icc:
+        # ICC profile
+        # according to PNG spec, the iCCP chunk contains:
+        # Profile name  1-79 bytes (character string)
+        # Null separator        1 byte (null character)
+        # Compression method    1 byte (0)
+        # Compressed profile    n bytes (zlib with deflate compression)
+        name = b"ICC Profile"
+        data = name + b"\0\0" + zlib.compress(icc)
+        chunk(fp, b"iCCP", data)
+
     if im.mode == "P":
         palette_byte_number = (2 ** bits) * 3
         palette_bytes = im.im.getpalette("RGB")[:palette_byte_number]
@@ -764,18 +776,6 @@ def _save(im, fp, filename, chunk=putchunk, check=0):
         for cid, data in info.chunks:
             chunk(fp, cid, data)
 
-    icc = im.encoderinfo.get("icc_profile", im.info.get("icc_profile"))
-    if icc:
-        # ICC profile
-        # according to PNG spec, the iCCP chunk contains:
-        # Profile name  1-79 bytes (character string)
-        # Null separator        1 byte (null character)
-        # Compression method    1 byte (0)
-        # Compressed profile    n bytes (zlib with deflate compression)
-        name = b"ICC Profile"
-        data = name + b"\0\0" + zlib.compress(icc)
-        chunk(fp, b"iCCP", data)
-
     ImageFile._save(im, _idat(fp, chunk),
                     [("zip", (0, 0)+im.size, 0, rawmode)])
 
diff --git a/Tests/test_file_png.py b/Tests/test_file_png.py
index cab0e01fa..fc6b07699 100644
--- a/Tests/test_file_png.py
+++ b/Tests/test_file_png.py
@@ -497,6 +497,25 @@ class TestFilePng(PillowTestCase):
         self.assertEqual(repr_png.format, 'PNG')
         self.assert_image_equal(im, repr_png)
 
+    def test_chunk_order(self):
+        im = Image.open("Tests/images/icc_profile.png")
+        test_file = self.tempfile("temp.png")
+        im.convert("P").save(test_file)
+
+        chunks = []
+        fp = open(test_file, "rb")
+        fp.read(8)
+        png = PngImagePlugin.PngStream(fp)
+        while True:
+            cid, pos, length = png.read()
+            chunks.append(cid)
+            try:
+                s = png.call(cid, pos, length)
+            except EOFError:
+                break
+            png.crc(cid, s)
+        self.assertLess(chunks.index(b"iCCP"), chunks.index(b"PLTE"))
+
 
 if __name__ == '__main__':
     unittest.main()