From 1d1f3be27acd50fc4b8184707d7f6223a3fde97f Mon Sep 17 00:00:00 2001
From: Alexander <homm86@gmail.com>
Date: Sun, 1 Dec 2019 20:34:05 +0300
Subject: [PATCH] unsupported modes

---
 Tests/test_image_reduce.py | 13 +++++++++++++
 src/libImaging/Reduce.c    |  6 ++++++
 2 files changed, 19 insertions(+)

diff --git a/Tests/test_image_reduce.py b/Tests/test_image_reduce.py
index a07d9c98c..bfa01d2bd 100644
--- a/Tests/test_image_reduce.py
+++ b/Tests/test_image_reduce.py
@@ -32,6 +32,19 @@ class TestImageReduce(PillowTestCase):
         with self.assertRaises(ValueError):
             im.reduce((0, 10))
 
+    def test_unsupported_modes(self):
+        im = Image.new("P", (10, 10))
+        with self.assertRaises(ValueError):
+            im.reduce(3)
+
+        im = Image.new("1", (10, 10))
+        with self.assertRaises(ValueError):
+            im.reduce(3)
+
+        im = Image.new("I;16", (10, 10))
+        with self.assertRaises(ValueError):
+            im.reduce(3)
+
     def get_image(self, mode):
         bands = [self.gradients_image]
         for _ in ImageMode.getmode(mode).bands[1:]:
diff --git a/src/libImaging/Reduce.c b/src/libImaging/Reduce.c
index 403e0bf68..630216ccc 100644
--- a/src/libImaging/Reduce.c
+++ b/src/libImaging/Reduce.c
@@ -963,6 +963,12 @@ ImagingReduce(Imaging imIn, int xscale, int yscale)
     ImagingSectionCookie cookie;
     Imaging imOut = NULL;
 
+    if (strcmp(imIn->mode, "P") == 0 || strcmp(imIn->mode, "1") == 0)
+        return (Imaging) ImagingError_ModeError();
+
+    if (imIn->type == IMAGING_TYPE_SPECIAL)
+        return (Imaging) ImagingError_ModeError();
+
     imOut = ImagingNewDirty(imIn->mode,
                             (imIn->xsize + xscale - 1) / xscale,
                             (imIn->ysize + yscale - 1) / yscale);