GribSharp.Jpeg2000 1.0.15

GribSharp

This project uses CSJ2K, which is distributed under the BSD 2-Clause License.

Copyright (c) 1999-2000 JJ2000 Partners; original C# port (c) 2007-2012 Jason S. Clary; C# encoding and adaptation to Portable Class Library with platform specific support (c) 2013-2016 Anders Gustafsson, Cureos AB

CSJ2K License: https://opensource.org/license/BSD-2-Clause

GribSharp is a pure C# library for reading and decoding GRIB2 (GRIdded Binary Edition 2) files used in meteorology, oceanography, and atmospheric modeling.

The library implements the core GRIB2 data representation templates and decoding algorithms in managed code, providing a lightweight and portable solution for .NET applications.

Features

• Pure C# implementation. The core package has zero external dependencies; JPEG2000 support is an opt-in add-on (CSJ2K). Compatible with Unity.

• Compatible with modern .NET runtimes.

• Reading of GRIB2 messages, sections, and metadata.

• Rich api for easy extraction.

• Direct api (more complex).

• Supports reading of GRIB2 files with missing values.

• Full support for GRIB2 files from NOAA NOMADS.

• Support for the following Data Representation Templates:

  • Simple Packing

    • Bit unpacking.
    • Value reconstruction using: value = (R + X × 2^E) / 10^D

  • IEEE Floating Point

    • Direct decoding of IEEE 32-bit floating-point values.

  • Complex Packing

    • Group references.
    • Variable bit widths.
    • Group-based decoding.
    • First- and second-order spatial differencing reconstruction.

  • JPEG2000 (optional GribSharp.Jpeg2000 add-on)

    • JPEG2000 codestream extraction.
    • Decoding through CSJ2K.
    • GRIB scaling and value reconstruction.

• Bitmap Section support:

  • Missing value handling.
  • Automatic conversion of undefined points to float.NaN.

• Dump Grib2 file to text

Packages

GribSharp ships as three NuGet packages so you only pull in the JPEG2000 dependency when you need it:

JPEG2000 activation is automatic: when the GribSharp.Jpeg2000 assembly is present, the core probes and registers its decoder on first use. For trimming/AOT scenarios where reflection is unreliable, call GribSharp.Jpeg2000.Jpeg2000Support.Register() once at startup. Without the add-on, template 5.40 throws GribNotSupportedException.

• CSJ2K — used exclusively by the add-on for decoding JPEG2000-compressed GRIB2 fields.

Goals

GribSharp aims to provide a lightweight, cross-platform, and easy-to-integrate GRIB2 decoding library for .NET applications without relying on native GRIB tooling.

Install

These packages are available on NuGet.

# Everything (drop-in, includes JPEG2000)
dotnet add package GribSharp

# Core only, no CSJ2K dependency
dotnet add package GribSharp.Core

# Core + JPEG2000 add-on
dotnet add package GribSharp.Core
dotnet add package GribSharp.Jpeg2000

Usage

Rich API:

using GribParser;
using GribParser.Model;

byte[] data = File.ReadAllBytes("gfs_forecast.grib2");
var file = Grib2Parser.ParseFile(data);

// List all available parameters
foreach (var name in file.ParameterNames)
    Console.WriteLine(name);

// Search by name (case-insensitive)
var temp = file.GetField("Temperature");
Console.WriteLine($"{temp.ParameterName} [{temp.Units}]: {temp.Values.Length} points");

// Search by enum (compile-time safe)
var rh = file[Parameter.RelativeHumidity];

// Search by level
var t2m = file.GetField(Parameter.Temperature, LevelType.HeightAboveGround, 2);
var t850 = file.GetField(Parameter.Temperature, LevelType.Isobaric, 85000);

// TryGet for optional parameters
if (file.TryGetField(Parameter.WindGust, out var gust))
    Console.WriteLine($"Racha máxima: {gust.Values.Max()} {gust.Units}");

// All fields of a parameter (ej: multiple level temperature)
var allTemps = file.GetFields(Parameter.Temperature);
foreach (var f in allTemps)
    Console.WriteLine($"  {f.LevelDescription} = {f.LevelValue}");

// Value at coordinates
float value = t2m.GetValueAt(lat: 40.41, lon: -3.70); // Madrid

Direct API:

using GribParser;
using GribParser.Model;

byte[] data = File.ReadAllBytes("gfs_forecast.grib2");
var messages = Grib2Parser.Parse(data);

byte[] data = File.ReadAllBytes("gfs_forecast.grib2");
var messages = Grib2Parser.Parse(data);

// Iterate messages and fields
foreach (var msg in messages)
{
    foreach (var f in msg.Fields)
    {
        Console.WriteLine($"{f.ParameterName} [{f.Units}] @ {f.LevelDescription} {f.LevelValue}");
        Console.WriteLine($"  Grid: {f.Grid.Ni}x{f.Grid.Nj}, Forecast +{f.ForecastTime}h");
    }

    // Search field inside a message
    if (msg.TryGetField("Temperature", out var temp))
        Console.WriteLine($"  Temp min={temp.Values.Min():F1} max={temp.Values.Max():F1}");
}

// Debug: dump wgrib2 style
Console.WriteLine(Grib2Dumper.Dump(data));