From 38365a44d04ce60b97f13b63e9eebb07c77fe010 Mon Sep 17 00:00:00 2001
From: "Christoph M. Becker" <cmbecker69@gmx.de>
Date: Sun, 5 Jan 2025 11:23:15 +0100
Subject: [PATCH] Add support for reading GIFs without colormap

Cf. <https://github.com/libgd/libgd/commit/fc38677e8005c24db891b84d3e84df7a199c979c>.

Closes GH-17364.
---
 NEWS                              |   2 ++
 ext/gd/libgd/gd_gif_in.c          |   6 ++++--
 ext/gd/tests/gif_nocolormaps.gif  | Bin 0 -> 37 bytes
 ext/gd/tests/gif_nocolormaps.phpt |  11 +++++++++++
 4 files changed, 17 insertions(+), 2 deletions(-)
 create mode 100644 ext/gd/tests/gif_nocolormaps.gif
 create mode 100644 ext/gd/tests/gif_nocolormaps.phpt

diff --git a/NEWS b/NEWS
index 1664d0a8d8105..816055b981828 100644
--- a/NEWS
+++ b/NEWS
@@ -22,6 +22,8 @@ PHP                                                                        NEWS
     images). (cmb)
   . Ported fix for libgd 223 (gdImageRotateGeneric() does not properly
     interpolate). (cmb)
+  . Added support for reading GIFs without colormap to bundled libgd. (Andrew
+    Burley, cmb)
 
 - Intl:
   . Fixed bug GH-11874 (intl causing segfault in docker images). (nielsdos)
diff --git a/ext/gd/libgd/gd_gif_in.c b/ext/gd/libgd/gd_gif_in.c
index 6fb79fd00b6ba..0204c4158db4a 100644
--- a/ext/gd/libgd/gd_gif_in.c
+++ b/ext/gd/libgd/gd_gif_in.c
@@ -244,8 +244,10 @@ gdImagePtr gdImageCreateFromGifCtx(gdIOCtxPtr fd) /* {{{ */
 					BitSet(buf[8], INTERLACE), &ZeroDataBlock);
 		} else {
 			if (!haveGlobalColormap) {
-				gdImageDestroy(im);
-				return 0;
+				// Still a valid gif, apply simple default palette as per spec
+				ColorMap[CM_RED][1] = 0xff;
+				ColorMap[CM_GREEN][1] = 0xff;
+				ColorMap[CM_BLUE][1] = 0xff;
 			}
 			ReadImage(im, fd, width, height,
 						ColorMap,
diff --git a/ext/gd/tests/gif_nocolormaps.gif b/ext/gd/tests/gif_nocolormaps.gif
new file mode 100644
index 0000000000000000000000000000000000000000..b3aa80d843a929ce4e5af18912072ba4157c115b
GIT binary patch
literal 37
kcmZ?wbhEHbWMp7u00PCIER0-0rVfY$7Gq-aVPvod09bhgj{pDw

literal 0
HcmV?d00001

diff --git a/ext/gd/tests/gif_nocolormaps.phpt b/ext/gd/tests/gif_nocolormaps.phpt
new file mode 100644
index 0000000000000..c962c0e9b20fd
--- /dev/null
+++ b/ext/gd/tests/gif_nocolormaps.phpt
@@ -0,0 +1,11 @@
+--TEST--
+A GIF without any Global or Local color tables is still decoded
+--EXTENSIONS--
+gd
+--FILE--
+<?php
+$im = imagecreatefromgif(__DIR__ . "/gif_nocolormaps.gif");
+var_dump($im instanceof GdImage);
+?>
+--EXPECT--
+bool(true)