diff --git a/htdocs/core/lib/images.lib.php b/htdocs/core/lib/images.lib.php
index 0f0ff2cf7be..bb874b7b6ec 100644
--- a/htdocs/core/lib/images.lib.php
+++ b/htdocs/core/lib/images.lib.php
@@ -1,7 +1,7 @@
 <?php
 /* Copyright (C) 2004-2010 Laurent Destailleur  <eldy@users.sourceforge.net>
  * Copyright (C) 2005-2007 Regis Houssin        <regis.houssin@inodbox.com>
- * Copyright (C) 2024		MDW							<mdeweerd@users.noreply.github.com>
+ * Copyright (C) 2024-2025	MDW							<mdeweerd@users.noreply.github.com>
  * Copyright (C) 2024       Frédéric France             <frederic.france@free.fr>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -315,6 +315,10 @@ function dol_imageResizeOrCrop($file, $mode, $newWidth, $newHeight, $src_x = 0,
 			break;
 	}
 
+	if ($img === null) {
+		return "Error: Could not create Image from '$filetoread'";
+	}
+
 	// Create empty image for target
 	if ($newExt == 'gif') {
 		// Compatibility image GIF
@@ -615,6 +619,7 @@ function vignette($file, $maxWidth = 160, $maxHeight = 120, $extName = '_small',
 
 	// Variable initialization according to image extension
 	$img = null;
+	$extImg = null;
 	switch ($infoImg[2]) {
 		case IMAGETYPE_GIF:	    // 1
 			$img = imagecreatefromgif($filetoread);
@@ -805,7 +810,7 @@ function vignette($file, $maxWidth = 160, $maxHeight = 120, $extName = '_small',
 			imagejpeg($imgThumb, $imgThumbName, $newquality); // @phan-suppress-current-line PhanTypeMismatchArgumentNullableInternal,PhanPossiblyUndeclaredVariable
 			break;
 		case IMAGETYPE_PNG:	    // 3
-			imagepng($imgThumb, $imgThumbName, $newquality);  // @phan-suppress-current-line PhanPossiblyUndeclaredVariable
+			imagepng($imgThumb, $imgThumbName, !is_numeric($newquality) ? -1 : (int) $newquality);  // @phan-suppress-current-line PhanPossiblyUndeclaredVariable
 			break;
 		case IMAGETYPE_BMP:	    // 6
 			// Not supported by PHP GD