From 21a23a0689c1582162ded0b913f495ea89c3be87 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Thu, 30 Nov 2023 16:17:04 +0100
Subject: [PATCH] pct2rgb.py: emit explicit exception when source file has no
 color table (fixes #8793)

---
 autotest/pyscripts/test_pct.py                | 23 +++++++++++++++++++
 swig/python/gdal-utils/osgeo_utils/pct2rgb.py |  2 ++
 2 files changed, 25 insertions(+)

diff --git a/autotest/pyscripts/test_pct.py b/autotest/pyscripts/test_pct.py
index d5c71f8b4de7..018bbf36f12a 100755
--- a/autotest/pyscripts/test_pct.py
+++ b/autotest/pyscripts/test_pct.py
@@ -170,6 +170,29 @@ def test_pct2rgb_1(script_path, tmp_path, rgb2pct1_tif):
     ori_ds = None
 
 
+###############################################################################
+# Test pct2rgb when invoked on a dataset without color table
+
+
+def test_pct2rgb_no_color_table(script_path, tmp_path, rgb2pct1_tif):
+    gdal_array = pytest.importorskip("osgeo.gdal_array")
+    try:
+        gdal_array.BandRasterIONumPy
+    except AttributeError:
+        pytest.skip("osgeo.gdal_array.BandRasterIONumPy is unavailable")
+
+    output_tif = str(tmp_path / "test_pct2rgb_no_color_table.tif")
+
+    from osgeo_utils import pct2rgb
+
+    with pytest.raises(Exception, match="has no color table"):
+        pct2rgb.pct2rgb(
+            src_filename="../gcore/data/byte.tif",
+            pct_filename=None,
+            dst_filename=output_tif,
+        )
+
+
 ###############################################################################
 # Test rgb2pct -n option
 
diff --git a/swig/python/gdal-utils/osgeo_utils/pct2rgb.py b/swig/python/gdal-utils/osgeo_utils/pct2rgb.py
index 987acc6f8aa9..d7fe81538ac1 100644
--- a/swig/python/gdal-utils/osgeo_utils/pct2rgb.py
+++ b/swig/python/gdal-utils/osgeo_utils/pct2rgb.py
@@ -84,6 +84,8 @@ def pct2rgb(
         ct = get_color_table(pal)
     else:
         ct = src_band.GetRasterColorTable()
+        if ct is None:
+            raise Exception(f"{src_filename} has no color table")
 
     ct_size = ct.GetCount()
     lookup = [