Windows Color Pattern Preview Tool

I need a lightweight Windows desktop application that helps me visualise colour schemes on several specific layout templates that I will supply. These templates rely on custom shapes rather than simple stripes or checks, so the program must let me load each pattern, try different fill colours, and see the final composite instantly before I commit to production.

Essential functions
• Native Windows 10/11 executable with no complex installation
• Template management: open or embed my custom‐shape files (SVG, PNG or a simple vector format)
• Colour controls: HEX and RGB input, palette picker, quick swap and undo
• Real-time preview panel with zoom and pan so what I see is truly what I get
• One-click export of the preview to PNG or JPEG at user-defined resolution

Deliverables
1. Compiled .exe ready to run
2. Clean, well-commented source code (C#, WPF, Python + PyQt, or similar is fine)
3. Short README explaining how to add or modify pattern templates

Acceptance Criteria
• At least three of my provided custom shape patterns preview correctly and export identically
• No crashes or visual glitches during colour changes and template switches
• Exported image matches the on-screen preview pixel for pixel

If you already have experience with small graphical utilities, colour simulation, or basic 2D rendering on Windows, this should be a straightforward build. I’m happy to clarify file formats and provide test assets once we begin.