From 77630f000cdf7efbbd0186702ac9d477677a2cd5 Mon Sep 17 00:00:00 2001
From: Andrew Murray <radarhere@users.noreply.github.com>
Date: Tue, 21 May 2019 06:08:57 +1000
Subject: [PATCH 1/3] Updated resampling filter error messages

---
 Tests/test_image_transform.py |  9 +++++++++
 src/PIL/Image.py              | 30 ++++++++++++++++++++++++++++--
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/Tests/test_image_transform.py b/Tests/test_image_transform.py
index ae1cf6e3d..384657d98 100644
--- a/Tests/test_image_transform.py
+++ b/Tests/test_image_transform.py
@@ -160,6 +160,15 @@ class TestImageTransform(PillowTestCase):
         im = hopper()
         self.assertRaises(ValueError, im.transform, (100, 100), None)
 
+    def test_unknown_resampling_filter(self):
+        im = hopper()
+        (w, h) = im.size
+        for resample in (Image.BOX, "unknown"):
+            self.assertRaises(ValueError, im.transform, (100, 100), Image.EXTENT,
+                              (0, 0,
+                               w, h),
+                              resample)
+
 
 class TestImageTransformAffine(PillowTestCase):
     transform = Image.AFFINE
diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index b9e569a83..c54e59833 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -1794,7 +1794,18 @@ class Image(object):
         if resample not in (
                 NEAREST, BILINEAR, BICUBIC, LANCZOS, BOX, HAMMING,
         ):
-            raise ValueError("unknown resampling filter")
+            message = "Unknown resampling filter ("+str(resample)+")."
+
+            filters = [filter[1]+" (%d)" % filter[0] for filter in (
+                (NEAREST, "Image.NEAREST"),
+                (LANCZOS, "Image.LANCZOS"),
+                (BILINEAR, "Image.BILINEAR"),
+                (BICUBIC, "Image.BICUBIC"),
+                (BOX, "Image.BOX"),
+                (HAMMING, "Image.HAMMING")
+            )]
+            raise ValueError(
+                message+" Use "+", ".join(filters[:-1])+" or "+filters[-1])
 
         size = tuple(size)
 
@@ -2263,7 +2274,22 @@ class Image(object):
             raise ValueError("unknown transformation method")
 
         if resample not in (NEAREST, BILINEAR, BICUBIC):
-            raise ValueError("unknown resampling filter")
+            if resample in (BOX, HAMMING, LANCZOS):
+                message = {
+                    BOX: "Image.BOX",
+                    HAMMING: "Image.HAMMING",
+                    LANCZOS: "Image.LANCZOS/Image.ANTIALIAS"
+                }[resample]+" (%d) cannot be used." % resample
+            else:
+                message = "Unknown resampling filter ("+str(resample)+")."
+
+            filters = [filter[1]+" (%d)" % filter[0] for filter in (
+                (NEAREST, "Image.NEAREST"),
+                (BILINEAR, "Image.BILINEAR"),
+                (BICUBIC, "Image.BICUBIC")
+            )]
+            raise ValueError(
+                message+" Use "+", ".join(filters[:-1])+" or "+filters[-1])
 
         image.load()
 

From 4fa3016d678d636366dfc37d10d65c297ea0340b Mon Sep 17 00:00:00 2001
From: Andrew Murray <3112309+radarhere@users.noreply.github.com>
Date: Thu, 6 Jun 2019 21:22:45 +1000
Subject: [PATCH 2/3] Changed string formatting

Co-Authored-By: Hugo <hugovk@users.noreply.github.com>
---
 src/PIL/Image.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index c54e59833..25450be5c 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -1794,7 +1794,7 @@ class Image(object):
         if resample not in (
                 NEAREST, BILINEAR, BICUBIC, LANCZOS, BOX, HAMMING,
         ):
-            message = "Unknown resampling filter ("+str(resample)+")."
+            message = "Unknown resampling filter ({}).".format(resample)
 
             filters = [filter[1]+" (%d)" % filter[0] for filter in (
                 (NEAREST, "Image.NEAREST"),
@@ -2279,7 +2279,7 @@ class Image(object):
                     BOX: "Image.BOX",
                     HAMMING: "Image.HAMMING",
                     LANCZOS: "Image.LANCZOS/Image.ANTIALIAS"
-                }[resample]+" (%d) cannot be used." % resample
+                }[resample]+" ({}) cannot be used.".format(resample)
             else:
                 message = "Unknown resampling filter ("+str(resample)+")."
 

From a94bd137915032889478efe0ae146a70be42f50d Mon Sep 17 00:00:00 2001
From: Andrew Murray <radarhere@users.noreply.github.com>
Date: Thu, 6 Jun 2019 21:33:12 +1000
Subject: [PATCH 3/3] Changed string formatting

---
 src/PIL/Image.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index 25450be5c..4e84fa53d 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -1796,7 +1796,7 @@ class Image(object):
         ):
             message = "Unknown resampling filter ({}).".format(resample)
 
-            filters = [filter[1]+" (%d)" % filter[0] for filter in (
+            filters = ["{} ({})".format(filter[1], filter[0]) for filter in (
                 (NEAREST, "Image.NEAREST"),
                 (LANCZOS, "Image.LANCZOS"),
                 (BILINEAR, "Image.BILINEAR"),
@@ -2281,9 +2281,9 @@ class Image(object):
                     LANCZOS: "Image.LANCZOS/Image.ANTIALIAS"
                 }[resample]+" ({}) cannot be used.".format(resample)
             else:
-                message = "Unknown resampling filter ("+str(resample)+")."
+                message = "Unknown resampling filter ({}).".format(resample)
 
-            filters = [filter[1]+" (%d)" % filter[0] for filter in (
+            filters = ["{} ({})".format(filter[1], filter[0]) for filter in (
                 (NEAREST, "Image.NEAREST"),
                 (BILINEAR, "Image.BILINEAR"),
                 (BICUBIC, "Image.BICUBIC")