From bdb6839a76bf4a7faa6f987a63e33189e3024c8f Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 1 Feb 2026 01:01:27 +0530
Subject: [PATCH] More useful error message when loading image from data fails

---
 src/calibre/utils/img.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/calibre/utils/img.py b/src/calibre/utils/img.py
index c8b3a1d51c..8612baa498 100644
--- a/src/calibre/utils/img.py
+++ b/src/calibre/utils/img.py
@@ -124,7 +124,14 @@ def image_from_data(data):
         q = what(None, data)
         if q == 'jxr':
             return load_jxr_data(data)
-        raise NotImage(f'Not a valid image (detected type: {q})')
+        ba = QByteArray(data)
+        buf = QBuffer(ba)
+        buf.open(QIODevice.OpenModeFlag.ReadOnly)
+        r = QImageReader(buf)
+        i = r.read()
+        buf.close()
+        if i.isNull():
+            raise NotImage(f'Not a valid image (detected type: {q}). Error: {r.errorString()}')
     return i