What causes "Invalid EXR image header" in SixLabors/ImageSharp?

Validate the source file with `exrheader` to confirm it is a well-formed EXR

SixLabors/ImageSharp · error · InvalidImageContentException

Invalid EXR image header

Error message

Invalid EXR image header

What it means

Thrown when the EXR decoder reads a header that fails structural validation — required attributes (channels, dataWindow, etc.) are missing, malformed, or the offset table is invalid. It is an InvalidImageContentException, meaning the input bytes do not form a valid EXR header.

Solutions

Validate the source file with `exrheader` to confirm it is a well-formed EXR
Re-obtain or re-export the file from the original source
Check that the stream length is complete (compare against expected file size) before decoding
If reading from a network stream, ensure the full file was downloaded (checksum)

Example fix

// before
var image = Image.Load(partialStream);
// after
if (stream.CanSeek && stream.Length < 8) throw new InvalidDataException("File too small to be EXR");
var image = Image.Load(stream); // may still throw for malformed headers

Defensive patterns

Strategy: try-catch

Validate before calling

// Basic sanity before decode
if (stream.CanSeek && stream.Length < 8) throw new InvalidDataException("Too small to be EXR");
// Optionally verify magic: 0x76 0x2F 0x31 0x01

Try / catch

try { return Image.Load(stream); }
catch (InvalidImageContentException ex) when (ex.Message.Contains("Invalid EXR image header")) { QuarantineAsset(ex); return null; }

Prevention

Verify checksums after download before decoding
Reject zero-length or suspiciously small files early
Use ImageSharp's built-in format detection rather than hardcoding the decoder
Quarantine and log files that fail header validation

When it happens

Trigger: Image.Load/DecodeAsync on bytes whose EXR attribute section ends prematurely, has a zero/invalid terminator, or lacks mandatory attributes; also called with a custom message for specific header violations.

Common situations: Truncated downloads, files renamed to .exr that are actually another format, EXR files written by broken/non-conformant tools, or memory-corrupted buffers.

Related errors

AI-assisted analysis of SixLabors/ImageSharp@59ce6af6fc (2026-09-13). Data as JSON: /api/errors/28ef71d924bdcd3d. Report an issue: GitHub.

Appendix: source

Thrown at src/ImageSharp/Formats/Exr/ExrThrowHelper.cs:26

/// <summary>
/// Cold path optimizations for throwing exr format based exceptions.
/// </summary>
internal static class ExrThrowHelper
{
    [DoesNotReturn]
    public static Exception NotSupportedDecompressor(string compressionType) => throw new NotSupportedException($"Not supported decoder compression method: {compressionType}");

    [DoesNotReturn]
    public static void ThrowInvalidImageContentException(string errorMessage) => throw new InvalidImageContentException(errorMessage);

    [DoesNotReturn]
    public static void ThrowNotSupportedVersion() => throw new NotSupportedException("Unsupported EXR version");

    [DoesNotReturn]
    public static void ThrowNotSupported(string msg) => throw new NotSupportedException(msg);

    [DoesNotReturn]
    public static void ThrowInvalidImageHeader() => throw new InvalidImageContentException("Invalid EXR image header");

    [DoesNotReturn]
    public static void ThrowInvalidImageHeader(string msg) => throw new InvalidImageContentException(msg);

    [DoesNotReturn]
    public static Exception NotSupportedCompressor(string compressionType) => throw new NotSupportedException($"Not supported encoder compression method: {compressionType}");
}

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