TinyEXR.NET

TinyEXR.NET is a pure C# port library of tinyexr

The target frameworks are net8.0, netstandard2.1

Download

TinyEXR.NET can be found on NuGet (← click it !)

Dependencies

The net8.0 target has no additional runtime dependencies.

The netstandard2.1 target depends on SharpZipLib.

Features

• full NativeAOT support!
• Single-part EXR read/write for scanline images.
• Single-part EXR read/write for tiled images, including one-level tiles and multi-resolution mipmap/ripmap layouts.
• Multipart image EXR parse/load/save for image parts.
• Deep single-part scanline EXR load through LoadDeepEXR.
• Regular image compression support for NONE, RLE, ZIP, ZIPS, PIZ, PXR24, B44, and B44A.
• Deep scanline compression support for NONE, RLE, ZIPS, and ZIP.
• Layer- and multiview-aware helpers such as EXRLayers and LoadEXRWithLayer, including RGBA expansion for subsampled channels in the convenience load path.
• Managed header/image models that preserve EXR metadata needed by tools and inspectors, including data/display windows, tile descriptions, custom attributes, channel sampling, line order, and long names.
• Full image decode for mixed multipart files that include deep or non-image parts. Current behavior is metadata-only for those parts.

Usage

TinyEXR.NET keeps its public API almost identical to tinyexr v1, so most functions and data structures can be mapped directly from the original library. The main differences are a small number of C#-oriented interfaces designed to avoid raw pointer-based usage and provide a more natural managed API surface.

Example:

ResultCode load = Exr.LoadEXR(inputPath, out float[] rgba, out int width, out int height);
if (load != ResultCode.Success)
{
    throw new InvalidOperationException($"LoadEXR failed: {load}");
}

Samples

The repository currently includes TinyEXR.Viewer, an Avalonia sample built on top of TinyEXR.NET.

The viewer is intended for manual EXR inspection: it can open EXR files from the file picker, drag and drop, or a command-line path, preview single-part images and pure-image multipart files, switch between parts/layers/levels when decoded image data is available, and display metadata such as version flags, windows, tile information, channels, custom attributes, and deep-image statistics.

See Samples/TinyEXR.Viewer/README.md for run instructions and the current feature boundaries.

Test

The current test suite covers the main supported surface of the library across both target outputs: the default target path and the netstandard2.1 fallback path run the same shared test cases.

See Test/README.md for the current test layout and execution details.

Benchmark

The repository includes memory-only benchmarks for the main read/write paths. Sample files are loaded during setup, so the timed results reflect decode/encode work on in-memory buffers rather than filesystem IO.

Updated on 2026-05-03. C# results use BenchmarkDotNet Mean; C++ baseline results use the Google Benchmark CPU column.

• CPU: 13th Gen Intel Core i7-13700K 3.40GHz
• OS: Windows 11 25H2 10.0.26200.8246
• .NET SDK/runtime: 10.0.203 / 10.0.7
• C# benchmark: BenchmarkDotNet 0.15.8, default job, workstation GC
• C++ compiler: MSVC 19.50.35730, Visual Studio 2026 18.5.2

Method	Sample	C# mean	C# allocated	C++ baseline	Managed / baseline
LoadEXRFromMemory	desk_scanline	40.05 ms	15.73 MB	38.65 ms	1.04x
SaveEXRToMemory	desk_scanline	108.77 ms	46.56 MB	164.06 ms	0.66x
LoadEXRImageFromMemory	desk_scanline	23.43 ms	7.15 MB	28.65 ms	0.82x
SaveEXRImageToMemory	desk_scanline	43.48 ms	80.90 MB	41.36 ms	1.05x
LoadEXRImageFromMemory	kapaa_multires	42.94 ms	21.27 MB	55.40 ms	0.78x
SaveEXRImageToMemory	kapaa_multires	169.49 ms	53.54 MB	213.54 ms	0.79x
LoadEXRMultipartImageFromMemory	beachball_multipart_0001	82.74 ms	30.65 MB	127.60 ms	0.65x
SaveEXRMultipartImageToMemory	beachball_multipart_0001	213.06 ms	78.32 MB	223.96 ms	0.95x
LoadDeepImageFromMemory	balls_deep_scanline	14.19 ms	5.47 MB	N/A	N/A

See Benchmark/README.md for more details.

Versioning

Starting with v1.0, TinyEXR.NET is a pure C# implementation of the tinyexr-compatible API surface.

The legacy v0.3.x line is kept as a maintenance branch. It may continue to receive compatibility fixes and follow tinyexr updates when needed, but no new features will be added to v0.3.x.

The main branch moves forward with v1.0+.

For new development, prefer the mainline v1.0+ branch. Use the v0.3.x maintenance branch only if you need the legacy native-wrapper line for compatibility reasons.

Upgrade from v0.3.x

• High-level RGBA helpers such as LoadEXR, LoadEXRFromMemory, SaveEXR, SaveEXRToMemory, LoadEXRWithLayer, and EXRLayers are still the recommended entry points, so code that only uses these helpers usually needs little or no change.
• IsExr and IsExrFromMemory are now IsEXR and IsEXRFromMemory.
• TinyEXR.Native.* and TinyEXR.Native.EXRNative are gone. The library is now a pure managed C# implementation, so the old native-runtime, P/Invoke, and static-link workflow from v0.3.x no longer applies.
• Native-style structs are replaced by managed types such as ExrVersion, ExrHeader, ExrImage, ExrMultipartHeader, ExrMultipartImage, ExrDeepImage, and ExrBox2i.
• Low-level read/write calls are now managed out-based APIs instead of ref-based native mutation. For example, ParseEXRHeaderFromFile(path, ref version, ref header) becomes ParseEXRHeaderFromFile(path, out ExrVersion version, out ExrHeader header), and LoadEXRImageFromFile(ref image, ref header, path) becomes LoadEXRImageFromFile(path, header, out ExrImage image).
• SaveEXRImageToMemory also changed shape: v0.3.x returned byte[]?, while the current API returns ResultCode and writes the payload to out byte[] encoded.

Known Limitation

Mixed multipart files that include deep or non-image parts are currently metadata-only for those parts; full image decode is supported for image parts.

License

TinyEXR.NET is under MIT license