From 8ccdc399df1254c89bdb4e8fda6d6daf98943ab6 Mon Sep 17 00:00:00 2001
From: Andrew Murray <3112309+radarhere@users.noreply.github.com>
Date: Wed, 11 Jun 2025 23:19:09 +1000
Subject: [PATCH] Remove padding between interleaved PCX palette data (#9005)

---
 Tests/images/p_4_planes.pcx | Bin 0 -> 136 bytes
 Tests/test_file_pcx.py      |   5 +++++
 src/libImaging/PcxDecode.c  |  22 ++++++++++++++++------
 3 files changed, 21 insertions(+), 6 deletions(-)
 create mode 100644 Tests/images/p_4_planes.pcx

diff --git a/Tests/images/p_4_planes.pcx b/Tests/images/p_4_planes.pcx
new file mode 100644
index 0000000000000000000000000000000000000000..8c5743a98554c89fa46188308332461a4aa87f91
GIT binary patch
literal 136
ocmd;LWn^T4f)s`n7?XkFKZ1#u#lpnE2!?o7;goD(XaLIr0O6ei;s5{u

literal 0
HcmV?d00001

diff --git a/Tests/test_file_pcx.py b/Tests/test_file_pcx.py
index 5d7fd1c1b..2e999eff6 100644
--- a/Tests/test_file_pcx.py
+++ b/Tests/test_file_pcx.py
@@ -37,6 +37,11 @@ def test_sanity(tmp_path: Path) -> None:
         im.save(f)
 
 
+def test_p_4_planes() -> None:
+    with Image.open("Tests/images/p_4_planes.pcx") as im:
+        assert im.getpixel((0, 0)) == 3
+
+
 def test_bad_image_size() -> None:
     with open("Tests/images/pil184.pcx", "rb") as fp:
         data = fp.read()
diff --git a/src/libImaging/PcxDecode.c b/src/libImaging/PcxDecode.c
index 942c8dc22..a65952fb1 100644
--- a/src/libImaging/PcxDecode.c
+++ b/src/libImaging/PcxDecode.c
@@ -60,15 +60,25 @@ ImagingPcxDecode(Imaging im, ImagingCodecState state, UINT8 *buf, Py_ssize_t byt
         }
 
         if (state->x >= state->bytes) {
-            if (state->bytes % state->xsize && state->bytes > state->xsize) {
-                int bands = state->bytes / state->xsize;
-                int stride = state->bytes / bands;
+            int bands;
+            int xsize = 0;
+            int stride = 0;
+            if (state->bits == 2 || state->bits == 4) {
+                xsize = (state->xsize + 7) / 8;
+                bands = state->bits;
+                stride = state->bytes / state->bits;
+            } else {
+                xsize = state->xsize;
+                bands = state->bytes / state->xsize;
+                if (bands != 0) {
+                    stride = state->bytes / bands;
+                }
+            }
+            if (stride > xsize) {
                 int i;
                 for (i = 1; i < bands; i++) {  // note -- skipping first band
                     memmove(
-                        &state->buffer[i * state->xsize],
-                        &state->buffer[i * stride],
-                        state->xsize
+                        &state->buffer[i * xsize], &state->buffer[i * stride], xsize
                     );
                 }
             }