Changed color handling

Author: rabanti-github

Changelog.md

@@ -1,5 +1,29 @@
 # Change Log
 
+## v3.0.0-rc.5
+
+---
+Release Date: **22.12.2025**
+
+- Added explicit operator for Address to convert from string to Address (string can be cast to address explicitly)
+- Added implicit operator for Range to convert from string to Range (string can be cast to range implicitly)
+- Introduced new class Color to handle colors in the Fill class. This class contains several color representations (implementations of the IColor interface):
+  - IndexedColor (representing indexed colors form index 0 to 65)
+  - SrgbColor (RGB or ARGB value)
+  - ThemeColor (Color, defined by theme elements)
+  - SystemColor (Color, defined by system colors)
+  - AutoColor (automatic color, no value / dummy class)
+- Re-implementation of the Fill class to use the new Color class for color representation of the foreground and background colors (indexed property removed)
+- Added implicit operator for Fill to create a fill color by a string (RGB or ARGB value)
+- Added implicit operator for Fill to create a fill color by an integer (indexed color value)
+- Changed internal handling of text cell values
+- Added static methods `bool Comparators.IsZero(double)` and `bool Comparators.IsZero(float)
+- Added `double ParserUtils.ParseDouble(string)` to parse doubles with invariant culture
+- Added `void Validators.ValidateGenericColor(string, bool = false)` to check generic color strings (RGB or ARGB)
+- Added test cases
+
+Note: Implicit address conversion from string to Address was not implemented, to avoid potential problems when comparing addresses (invalid strings could raise exceptions instead of returning false in  the equals method). This does not apply to the Range struct
+
 ## v3.0.0-rc.3 + v3.0.0-rc.4
 
 ---

MigrationGuide.md

@@ -22,7 +22,7 @@ The following guide lists all necessary changes, as well as changed behaviors of
   - The method `Workbook.AddStyle(Style)` was completely removed, after marked as obsolete in version 2.x. Styles should be added directly to cells or ranges. 
   - The method `Workbook.AddStyleComponent(Style, AbstractStyle)` was completely removed, after marked as obsolete in version 2.x. Styles should be modified directly on cells, e.g. `workbook.CurrentWorksheet.Cells["A1"].CellStyle.CurrentFont.Bold = true;` or `workbook.CurrentWorksheet.Cells["A1"].CellStyle.Append(fontStyle)`. 
   - The methods `Workbook.RemoveStyle(Style)`, `Workbook.RemoveStyle(Style, bool)`, `Workbook.RemoveStyle(string)` and `Workbook.RemoveStyle(string, bool)` were completely removed, after marked as obsolete in version 2.x. Styles should be removed directly from cells (e.g. `workbook.CurrentWorksheet.Cells["A1"].RemoveStyle()`.
-
+  - The method `Workbook.GetMruColors()` returns now a `IReadOnlyList<Color>` (was string). The new Color class (namespace `NanoXLSX.Colors`) can represent an RGB, ARGB, system, theme or indexed color. See the Color class documentation for more details. 
 ---
 
 ### Worksheet
@@ -230,12 +230,14 @@ ApplicationDefined, ANSI, Default, Symbols, Mac, ShiftJIS, Hangul, Johab, GBK, B
 
 #### Fill
 
+Fill was completely overhauled in version 3.0.0, to support more flexible color definitions, like (A)RGB, indexed colors, theme or system colors, as well as tint.
+
 - The public constant values of the `Fill` class were renamed, according to the following overview:
 
 | Old Constant             | New Constant           | Remarks  |
 |--------------------------|------------------------|----------|
-| `DEFAULT_COLOR`          | `DefaultColor`         |          |
-| `DEFAULT_INDEXED_COLOR`  | `DefaultIndexedColor`  |          |
+| `DEFAULT_COLOR`          | `DefaultColor`         | The type was changed from `string` to an instance of `SrgbColor` with `FF000000` as ARGB value |
+| `DEFAULT_INDEXED_COLOR`  | `DefaultIndexedColor`  | The type was changed from `int` to an instance of `IndexedColor` with the `64` as index value |
 | `DEFAULT_PATTERN_FILL`   | `DefaultPatternFill`   |          |
 
 - The enum values of `Fill.FillType` were renamed, according to the following overview:
@@ -258,6 +260,23 @@ ApplicationDefined, ANSI, Default, Symbols, Mac, ShiftJIS, Hangul, Johab, GBK, B
 | `PatternValue.none`      | `PatternValue.None`        |         |
 
 - The static method `Fill.ValidateColr(string,bool, bool)` was moved to the utils class `Validators.ValidateColr(string,bool, bool)` in namespace `NanoXLSX.Utils`. The class has to be changed in the code, but the method signature remains unchanged.
+- The property `Fill.BackgroundColor` was changed from type `string` to the new `Color` class (namespace `NanoXLSX.Colors`). The new Color class can represent an RGB, ARGB, system, theme or indexed color. See the Color class documentation for more details.
+- The property `Fill.ForegroundColor` was changed from type `string` to the new `Color` class (namespace `NanoXLSX.Colors`). The new Color class can represent an RGB, ARGB, system, theme or indexed color. See the Color class documentation for more details.
+- The property `IndexedColor` was removed and is now part of the new `Color` class, applied to `BackgroundColor` and `ForegroundColor`. In the `Color` class, there is a property `IndexedColor` that holds an object of the type `IndexedColor` (namespace `NanoXLSX.Themes`). The original `int` value has to be replaced by one of the available enum values in the class `IndexedColor`. Usage example:
+
+```csharp
+Fill fill = new Fill();
+fill.ForegroundColor = Color.CreateIndexed(IndexedColor.Value.Yellow);
+
+// Different examples with other color types:
+Fill fill2 = new Fill();
+fill2.BackgroundColor = Color.CreateRgb("FF00FF00"); // ARGB
+
+Fill fill3 = new Fill();
+fill3.ForegroundColor = Color.CreateTheme(Theme.ColorSchemeElement.Accent1, 0.5f); // Theme color with tint
+
+```
+
 
 #### CellXf
 

NanoXLSX.Core/Address.cs

@@ -222,6 +222,15 @@ public int CompareTo(Address other)
             return left.CompareTo(right) >= 0;
         }
 
+        /// <summary>
+        /// Explicit conversion from string to Address
+        /// </summary>
+        /// <param name="address">Address expression</param>
+        public static explicit operator Address(string address)
+        {
+            return new Address(address);
+        }
+
         /// <summary>
         /// Creates a (dereferenced, if applicable) deep copy of this address
         /// </summary>

NanoXLSX.Core/Colors/AutoColor.cs

@@ -0,0 +1,28 @@
+/*
+ * NanoXLSX is a small .NET library to generate and read XLSX (Microsoft Excel 2007 or newer) files in an easy and native way
+ * Copyright Raphael Stoeckli © 2025
+ * This library is licensed under the MIT License.
+ * You find a copy of the license in project folder or on: http://opensource.org/licenses/MIT
+ */
+
+using NanoXLSX.Interfaces;
+
+namespace NanoXLSX.Colors
+{
+    /// <summary>
+    /// Class representing an automatic color. 
+    /// </summary>
+    /// \remark <remarks>This class does not carry any value. It is only for the purpose of identification.</remarks>
+    public class AutoColor : IColor
+    {
+        /// <summary>
+        /// Static instance of the AutoColor class to avoid multiple instances (instances does not deviate)
+        /// </summary>
+        public static readonly AutoColor Instance = new AutoColor();
+
+        /// <summary>
+        /// The string value of an auto color is always null
+        /// </summary>
+        public string StringValue => null;
+    }
+}