GaussianFit.Core 1.1.0

GaussianFit.Core

A small .NET Standard 2.0 library for 2D Gaussian fitting from System.Drawing.Bitmap inputs.
Designed for laser / beam profile analysis, with optional ROI-based fitting while preserving original image coordinates.

Works on .NET Framework 4.6.1+ and modern .NET (6/7/8).

🚀 Install

dotnet add package GaussianFit.Core

💻 Quick Start (Full Image)

using GaussianFit.Core;


var result = GaussianFitter.Run("beam.png", new FitOptions {
Mode = PrepMode.EdgeMean_BorderPct,
BorderPercent = 10,
CutoffPercent = 30,
MaxIterations = 200  
});


Console.WriteLine(result.ReportText);

Example output:

A (amplitude)    =  215.63
x0, y0           =  123.4,   98.5
σx, σy           =  12.1,   11.9
RMSE             =  0.024
nRMSE (RMSE/A)   =  1.12 % [Excellent]

✂️ Quick Start (With ROI)

You can limit the fitting area using a Region of Interest (ROI) while still obtaining the beam center in original image coordinates.

using GaussianFit.Core;

var roi = new RoiRect(x: 202, y: 163, w: 750, h: 750);

var result = GaussianFitter.Run("beam.png", roi, new FitOptions {
    Mode = PrepMode.EdgeMean_BorderPct,
    BorderPercent = 10,
    CutoffPercent = 30,
    MaxIterations = 200  
});

// Center in ORIGINAL image coordinates
Console.WriteLine($"Center (orig): x={result.X0:F2}, y={result.Y0:F2}");

Internally:

• The image is cropped to the ROI for fitting
• The fit is performed in local (crop) coordinates
• The final (x0, y0) is automatically converted back to the original image coordinate system

This avoids edge-light contamination while keeping coordinates consistent.

⚙️ Configuration Options

📈 Algorithm Overview

The 2D Gaussian model is defined as:

f(x, y) = A · exp( -((x − x₀)² / (2σₓ²) + (y − y₀)² / (2σᵧ²)) ) + C

where:

The library minimizes the Sum of Squared Errors (SSE) between the measured data and the model using a Levenberg–Marquardt optimizer.

🎯 Visualization Guide

When drawing overlays (as in the WinForms demo):

• 🟢 Green ellipse = 1σ boundary (~68% energy)
• 🟠 Orange ellipse = FWHM / 2 radius (~1.177σ)
• 🔵 Blue ellipse = 1/e² boundary (radius = 2σ)

Overlay coordinates are provided in ROI-local space when ROI is used, which simplifies drawing on cropped preview images.

🧠 Typical Use Cases

1. Laser / optical beam profiling
2. Fiber-coupled source alignment
3. Spot size and FWHM measurement
4. Image-based Gaussian fitting in production or lab environments

📦 Versioning Notes

• v1.1.0
  • Added optional ROI-based fitting
  • Preserves original image coordinates for (x0, y0)
  • Added ROI metadata to FitResult

📜 License

MIT License © 2025 Napat Sutikant