From 35d7af83bd778bab2072b58d0e15d7adc283d236 Mon Sep 17 00:00:00 2001
From: Ritika shrestha <87307821+ritsth@users.noreply.github.com>
Date: Mon, 20 Jul 2026 18:01:32 -0700
Subject: [PATCH 1/2] Raise ValueError instead of asserting on FTEX format
 count

---
 Tests/test_file_ftex.py    | 12 ++++++++++++
 src/PIL/FtexImagePlugin.py |  4 +++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/Tests/test_file_ftex.py b/Tests/test_file_ftex.py
index fdd7b375762..0130651b1bf 100644
--- a/Tests/test_file_ftex.py
+++ b/Tests/test_file_ftex.py
@@ -38,3 +38,15 @@ def test_invalid_texture() -> None:
     with pytest.raises(ValueError, match="Invalid texture compression format: 2"):
         with Image.open(io.BytesIO(data)):
             pass
+
+
+def test_invalid_format_count() -> None:
+    with open("Tests/images/ftex_dxt1.ftc", "rb") as fp:
+        data = fp.read()
+
+    # Change the format count to an unsupported value
+    data = data[:20] + struct.pack("<i", 2) + data[24:]
+
+    with pytest.raises(ValueError, match="Unsupported number of formats: 2"):
+        with Image.open(io.BytesIO(data)):
+            pass
diff --git a/src/PIL/FtexImagePlugin.py b/src/PIL/FtexImagePlugin.py
index e4d836cbdb2..6c792a9b097 100644
--- a/src/PIL/FtexImagePlugin.py
+++ b/src/PIL/FtexImagePlugin.py
@@ -82,7 +82,9 @@ def _open(self) -> None:
 
         # Only support single-format files.
         # I don't know of any multi-format file.
-        assert format_count == 1
+        if format_count != 1:
+            msg = f"Unsupported number of formats: {format_count}"
+            raise ValueError(msg)
 
         format, where = struct.unpack("<2i", self.fp.read(8))
         self.fp.seek(where)

From b4a82a8b52dbbc2132d29de8d5ae371114bf5f7e Mon Sep 17 00:00:00 2001
From: Ritika shrestha <87307821+ritsth@users.noreply.github.com>
Date: Wed, 22 Jul 2026 11:54:07 -0700
Subject: [PATCH 2/2] Specify "texture formats" in error message

---
 Tests/test_file_ftex.py    | 10 ++++------
 src/PIL/FtexImagePlugin.py |  2 +-
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/Tests/test_file_ftex.py b/Tests/test_file_ftex.py
index 0130651b1bf..99cf36a6ffe 100644
--- a/Tests/test_file_ftex.py
+++ b/Tests/test_file_ftex.py
@@ -40,13 +40,11 @@ def test_invalid_texture() -> None:
             pass
 
 
-def test_invalid_format_count() -> None:
+def test_unsupported_texture_format_count() -> None:
     with open("Tests/images/ftex_dxt1.ftc", "rb") as fp:
-        data = fp.read()
-
-    # Change the format count to an unsupported value
-    data = data[:20] + struct.pack("<i", 2) + data[24:]
+        # Change the format count to an unsupported value
+        data = fp.read(20) + struct.pack("<i", 2)
 
-    with pytest.raises(ValueError, match="Unsupported number of formats: 2"):
+    with pytest.raises(ValueError, match="Unsupported number of texture formats: 2"):
         with Image.open(io.BytesIO(data)):
             pass
diff --git a/src/PIL/FtexImagePlugin.py b/src/PIL/FtexImagePlugin.py
index 6c792a9b097..3137d200129 100644
--- a/src/PIL/FtexImagePlugin.py
+++ b/src/PIL/FtexImagePlugin.py
@@ -83,7 +83,7 @@ def _open(self) -> None:
         # Only support single-format files.
         # I don't know of any multi-format file.
         if format_count != 1:
-            msg = f"Unsupported number of formats: {format_count}"
+            msg = f"Unsupported number of texture formats: {format_count}"
             raise ValueError(msg)
 
         format, where = struct.unpack("<2i", self.fp.read(8))