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CharLS .NET

CharLS .NET is a C# JPEG-LS library implementation.
JPEG-LS (ISO-14495-1) is a lossless/near-lossless compression standard for continuous-tone images.

Features

.NET 8.0 class library.
Support for the .NET platforms: Windows, Linux and macOS.

Performance

A couple of benchmarks have been executed to assist to decide which codec to use. The following codecs were measured:

Codec	Version	Release date	Description
CharLS.Managed	0.8.0	2024-08-23	C# implementation
CharLS.Native	3.2.0	2023-09-24	C# wrapper around C++ implementation
cscharls	0.1.1	2017-04-24	C# implementation
charls-js	2.1.1	2021-10-07	WebAssembly implementation based on C++ source

and the following test images were used:

Image name	Width	Height	Bits per sample	Components	Description
Tulips	512	512	8	1	Monochrome image of tulips
MG1	3064	4664	12	1	Monochrome medical image
Delta E	3072	2048	8	3	Artificial RGB image

The benchmarks were performed on 2 hardware platforms: x86 and ARM64.
The column 'NEAR' defines the allowed error, 0 means lossless encoding.
The column 'ILV' defines the interleave mode used to encode the image.

x86-64 Platform

Characteristics of the test environment: AMD Ryzen 9 5950X, .NET 8.0.8 (X64 RyuJIT AVX2)
WebAssembly engine: Chrome V8 12.8.374.21

Operation	ILV	CharLS.Managed	CharLS.Native	cscharls	charls-js
Decode Tulips	None	5.0 ms	3.6 ms	10.4 ms	5.6 ms
Decode MG1	None	292.3 ms	205.0 ms	676.3 ms	335.2 ms
Decode Delta E	Sample	80.0 ms	89.4 ms	-	89.5 ms
Encode Tulips	None	7.1 ms	4.7 ms	11.8 ms	-
Encode MG1	None	404.3 ms	256.3 ms	695.8 ms	-

Arm64 Platform

Characteristics of the test environment: Snapdragon Compute Platform, .NET 8.0.8 (Arm64 RyuJIT AdvSIMD)
WebAssembly engine: Chrome V8 12.8.374.21

Operation	ILV	CharLS.Managed	CharLS.Native	cscharls	charls-js
Decode Tulips	None	7.2 ms	4.7 ms	14.3 ms	10.5 ms
Decode MG1	None	431.7 ms	261.8 ms	1019.4 ms	542.1 ms
Encode Tulips	None	9.6 ms	5.5 ms	15.7 ms	-
Encode MG1	None	564.0 ms	318.6 ms	1017.2 ms	-

How to use

CharLS.Managed can be added to your C# project using the dotnet command line or the NuGet Package Manager in Visual Studio.

Install using the dotnet command line

dotnet add package CharLS.Managed

How to use the C# classes in the NuGet package

A sample application is included in the GitHub repository that demonstrates how to convert common image types like .bmp, .png and .jpg to .jls (JPEG-LS).

General steps to build this repository

Use Git to get a clone of this repository:

 git clone https://github.com/team-charls/charls-dotnet.git

Use the .NET 8.0 CLI or Visual Studio 2022 (v17.11 or newer) to build the solution file CharLSDotNet.sln.
For example: dotnet build && dotnet test && dotnet publish to build the NuGet package.
Building can be done on all supported .NET SDK platforms: Windows, Linux or macOS

Code signing the assembly and the NuGet package

Building the NuGet package with a signed assembly DLL and NuGet package can only be done on the Window platform with Visual Studio 2022 or with Build tools for Visual Studio 2022. To support code signing with a code signing certificate, stored on a smart card, a Windows command file is available: create-signed-nuget-package.cmd. Instructions:

Open a Visual Studio Developer Command Prompt
Go the root of the cloned repository
Ensure the code signing certificate is available
Execute the command create-signed-nuget-package.cmd certificate-thumb-print time-stamp-url
The certificate thumbprint and time stamp URL arguments are depending on the used code signing certificate.

All assembly DLLs and the NuGet package itself will be signed.

About the JPEG-LS image compression standard

More information about JPEG-LS can be found in the README from the C++ CharLS project.