Added DisableImageFunctionDownloads property to ExcelCalculationOption

src/EPPlus/FormulaParsing/DependencyChain/RpnOptimizedDependencyChain.cs

@@ -44,6 +44,7 @@ public RpnOptimizedDependencyChain(ExcelWorkbook wb, ExcelCalculationOption opti
                 config.CacheExpressions = options.CacheExpressions;
                 config.PrecisionAndRoundingStrategy = options.PrecisionAndRoundingStrategy;
                 config.AlwaysRefreshImageFunction = options.AlwaysRefreshImageFunction;
+                config.DisableImageFunctionDownloads = options.DisableImageFunctionDownloads;
                 config.EnableUnicodeAwareStringOperations = options.EnableUnicodeAwareStringOperations;
             });
 

src/EPPlus/FormulaParsing/ExcelCalculationOption.cs

@@ -116,6 +116,13 @@ public bool AlwaysRefreshImageFunction
             set; 
         } = false;
 
+        /// <summary>
+        /// If true the IMAGE function will never download external content in formula calculation.
+        /// It will instead return the NAME error as if the function was not implemented.
+        /// NB! This property overrides the <see cref="AlwaysRefreshImageFunction"/> property if set to true.
+        /// </summary>
+        public bool DisableImageFunctionDownloads { get; set; } = false;
+
         /// <summary>
         /// Enables Unicode-aware string operations, ensuring correct handling of surrogate pairs for comparisons, substrings, and sorting within the library.
         /// </summary>

src/EPPlusTest/FormulaParsing/Excel/Functions/RefAndLookup/ImageFunctionTests.cs

@@ -148,5 +148,20 @@ public void ImageTest_ShouldReturnNameErrorWhenServiceIsNull()
 
             Assert.AreEqual(ExcelErrorValue.Create(eErrorType.Name), sheet.Cells["A1"].Value);
         }
+
+        [TestMethod]
+        public void ImageTest_ShouldNotDownloadWhenDownloadsDisabled()
+        {
+            using var package = new ExcelPackage();
+            var httpsService = new TestHttpsService();
+            package.Settings.ImageFunctionService = httpsService;
+            var sheet = package.Workbook.Worksheets.Add("Sheet1");
+            sheet.Cells["A1"].Formula = "IMAGE(\"https://epplussoftware.com/img/EPPlus-logo-full.png\", \"Alt text\", 1)";
+
+            sheet.Calculate(opt => opt.DisableImageFunctionDownloads = true);
+
+            Assert.AreEqual(0, httpsService.NumberOfCalls, "the download service should not be called when downloads are disabled");
+            Assert.AreEqual(ExcelErrorValue.Create(eErrorType.Name), sheet.Cells["A1"].Value);
+        }
     }
 }