From f57a07e15a87860f928844c528a10ca94d76cc1c Mon Sep 17 00:00:00 2001
From: Ryan Cramer <ryan@processwire.com>
Date: Thu, 29 Dec 2022 12:20:20 -0500
Subject: [PATCH] Attempt fix for processwire/processwire-issues#1299 using
 @adrianbj suggestion

---
 wire/core/ImageSizerEngineGD.php | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/wire/core/ImageSizerEngineGD.php b/wire/core/ImageSizerEngineGD.php
index 1881658a..d31b45a6 100755
--- a/wire/core/ImageSizerEngineGD.php
+++ b/wire/core/ImageSizerEngineGD.php
@@ -862,12 +862,13 @@ class ImageSizerEngineGD extends ImageSizerEngine {
 		} else if($this->imageType == IMAGETYPE_GIF) {
 			// @mrx GIF transparency
 			$transparentIndex = imagecolortransparent($image);
-			// $transparentColor = $transparentIndex != -1 ? @imagecolorsforindex($image, $transparentIndex) : 0;
-			$transparentColor = $transparentIndex != -1 ? imagecolorsforindex($image, ($transparentIndex < imagecolorstotal($image) ? $transparentIndex : $transparentIndex - 1)) : 0;
-			if(!empty($transparentColor)) {
-				$transparentNew = imagecolorallocate($im, $transparentColor['red'], $transparentColor['green'], $transparentColor['blue']);
-				$transparentNewIndex = imagecolortransparent($im, $transparentNew);
-				imagefill($im, 0, 0, $transparentNewIndex);
+			if($transparentIndex >= 0 && $transparentIndex < imagecolorstotal($image)) {
+				$transparentColor = imagecolorsforindex($image, $transparentIndex);
+				if(!empty($transparentColor)) {
+					$transparentNew = imagecolorallocate($im, $transparentColor['red'], $transparentColor['green'], $transparentColor['blue']);
+					$transparentNewIndex = imagecolortransparent($im, $transparentNew);
+					imagefill($im, 0, 0, $transparentNewIndex);
+				}
 			}
 
 		} else {