# How OfficeCLI ThemeColorResolver Handles Office and User-Defined Theme Colors > Discover how OfficeCLI's ThemeColorResolver converts Office and user theme colors into hex dictionaries, supporting format specific aliases for PowerPoint and Word. - Repository: [OfficeAI/OfficeCLI](https://github.com/iofficeai/OfficeCLI) - Tags: internals - Published: 2026-07-08 --- **The ThemeColorResolver is a static utility in OfficeCLI that converts OOXML ColorScheme objects into validated hexadecimal color dictionaries, supporting both standard Office theme slots and user-defined color schemes with format-specific aliases for PowerPoint and Word.** OfficeCLI is an open-source command-line tool for manipulating Office documents, and one of its critical components is the **ThemeColorResolver** located in [`src/officecli/Core/ThemeColorResolver.cs`](https://github.com/iOfficeAI/OfficeCLI/blob/main/src/officecli/Core/ThemeColorResolver.cs). This utility bridges the gap between Office's complex XML-based color schemes and the plain hexadecimal values needed for rendering, ensuring safe color extraction across PowerPoint and Word pipelines. ## Input Validation and Safety Checks The **ThemeColorResolver** begins its workflow in the `BuildColorMap` method with rigorous input validation. When receiving a `Drawing.ColorScheme?` object (the theme definition) and the `includePptAliases` flag, the resolver immediately returns an empty dictionary if the scheme is null, preventing null reference exceptions downstream. Before any color values enter the system, the private helper `IsHex` performs a security validation on lines 24-31. This method guarantees that every color value is a valid 3-, 6-, or 8-character hexadecimal string. This validation serves as a critical security barrier, preventing malformed or malicious theme files from injecting XSS vectors into CSS-style strings that could compromise rendering pipelines. ## Core Scheme Color Extraction The resolver extracts colors from eleven standard scheme slots defined in the OOXML specification: `dk1`, `dk2`, `lt1`, `lt2`, `accent1` through `accent6`, `hlink`, and `folHlink`. For each slot in the `Add` local function (lines 39-50), the code performs the following sequence: 1. Retrieves the first child `RgbColorModelHex` element for explicit RGB values 2. Falls back to `SystemColor` for theme-defined system colors 3. Selects the first non-null hexadecimal value (`rgb ?? srgb`) 4. Validates through `IsHex` before adding to the dictionary The actual population occurs in lines 52-64, where each validated color is inserted into a case-insensitive dictionary under its canonical name. ## Alias Management for Word and PowerPoint To make the color map ergonomically usable across different Office formats, **ThemeColorResolver** automatically generates shared aliases on lines 65-69. These aliases map technical scheme names to practical usage names: - **dk1** → `tx1`, `dark1` - **dk2** → `dark2` - **lt1** → `bg1`, `light1` - **lt2** → `bg2`, `light2` These aliases apply to both Word and PowerPoint processing, ensuring consistent naming conventions when downstream code references text colors (`tx1`) or background colors (`bg1`). ## PowerPoint-Specific Extensions When the `includePptAliases` parameter is set to `true`—which the PowerPoint pipeline passes on lines 71-78—the resolver appends additional aliases that reflect PowerPoint's specific naming conventions: - **dk1** → `text1` - **dk2** → `text2`, `tx2` - **lt1** → `background1` - **lt2** → `background2` This conditional block isolates PowerPoint-specific terminology from Word's slimmer alias set, allowing the same core resolver to serve both formats without polluting Word's color map with unused PowerPoint names. ## Usage Examples ### Word Document Color Extraction For Word documents, call `BuildColorMap` without PowerPoint aliases: ```csharp using DocumentFormat.OpenXml.Presentation; using OfficeCli.Core; // themePart is the OpenXml part containing the theme definition var colorScheme = themePart.Theme?.ThemeElements?.ColorScheme; var map = ThemeColorResolver.BuildColorMap(colorScheme); // map contains: "dk1", "accent3", "tx1", "bg2", etc. ``` ### PowerPoint Slide Color Extraction For PowerPoint processing, enable the format-specific aliases: ```csharp using DocumentFormat.OpenXml.Presentation; using OfficeCli.Core; // themePart comes from the PPTX package var colorScheme = themePart.Theme?.ThemeElements?.ColorScheme; var map = ThemeColorResolver.BuildColorMap(colorScheme, includePptAliases: true); // map additionally contains: "text1", "background2", etc. ``` ### Safe HTML Generation Use the validated map to generate CSS-safe color styles: ```csharp string hex = map["accent1"]; // e.g., "FF5733" string style = $"color: #{hex};"; // safe because hex was validated htmlBuilder.Append($"

Content

"); ``` ## Implementation Details and Security The **ThemeColorResolver** architecture emphasizes three core principles: - **Safety through validation**: The `IsHex` check eliminates malformed theme data before string interpolation, mitigating XSS risks. - **Format extensibility**: Working on the generic `Drawing.ColorScheme` type allows any future Office format exposing compatible OOXML color schemes to reuse this logic. - **Pure function design**: The resolver contains no UI or file-IO dependencies, making it trivial to unit test with mocked color scheme objects. ## Summary - **ThemeColorResolver** in [`src/officecli/Core/ThemeColorResolver.cs`](https://github.com/iOfficeAI/OfficeCLI/blob/main/src/officecli/Core/ThemeColorResolver.cs) provides a static `BuildColorMap` method for converting OOXML themes to hexadecimal dictionaries. - The `IsHex` validation ensures all output colors are safe 3-, 6-, or 8-character hexadecimal strings before entering rendering pipelines. - The resolver handles eleven standard color slots including `dk1`, `lt2`, and `accent1` through `accent6`. - Shared aliases (`tx1`, `bg1`, `dark1`, etc.) support both Word and PowerPoint, while optional PowerPoint-specific aliases (`text1`, `background2`) activate via the `includePptAliases` parameter. - User-defined themes from [`theme1.xml`](https://github.com/iOfficeAI/OfficeCLI/blob/main/theme1.xml) files process identically to built-in Office themes, as both expose the same `ColorScheme` object structure. ## Frequently Asked Questions ### What is ThemeColorResolver in OfficeCLI? **ThemeColorResolver** is a static helper class located in [`src/officecli/Core/ThemeColorResolver.cs`](https://github.com/iOfficeAI/OfficeCLI/blob/main/src/officecli/Core/ThemeColorResolver.cs) that translates OOXML ColorScheme objects into sanitized dictionaries mapping color names to hexadecimal values. It serves as the central authority for color extraction across OfficeCLI's PowerPoint and Word processing modules. ### How does ThemeColorResolver validate color safety? The resolver uses a private `IsHex` method (lines 24-31) to verify that every color value is a valid 3-, 6-, or 8-character hexadecimal string before adding it to the output dictionary. This prevents malformed or malicious theme data from propagating into CSS strings that could become XSS vectors. ### What is the difference between Word and PowerPoint color handling in OfficeCLI? Word processing uses the base color map with shared aliases like `tx1` and `bg1`, while PowerPoint processing passes `includePptAliases: true` to `BuildColorMap` to receive additional format-specific names such as `text1`, `text2`, and `background1`. This allows both formats to use intuitive naming conventions while sharing the same underlying validation logic. ### Does ThemeColorResolver support custom user-defined themes? Yes. The resolver processes any `Drawing.ColorScheme` object that follows the OOXML specification, including user-defined themes from custom [`theme1.xml`](https://github.com/iOfficeAI/OfficeCLI/blob/main/theme1.xml) files. Since the extraction logic relies on the standard OOXML structure rather than hardcoded Office defaults, custom accent colors and modified dark/light variants resolve identically to built-in themes.