SixLabors/ImageSharp · error · InvalidImageContentException

{errorMessage}

Error message

{errorMessage}

What it means

This is the generic PNG content-error entry point in PngThrowHelper. SixLabors.ImageSharp throws InvalidImageContentException when the PNG stream being decoded violates the PNG specification in a way not covered by a more specific helper, so the decoder aborts rather than return a corrupt image. The message is supplied by the caller, so read the exception message for the exact problem.

Solutions

1. Read the exception message to identify the specific PNG violation, then fix or regenerate the source image.
2. Verify the file is a genuine PNG (starts with the 8-byte PNG signature) and is not truncated.
3. Validate the image with an external tool (e.g. pngcheck) before loading.
4. Wrap the load call in a try-catch for InvalidImageContentException and handle untrusted/corrupt input gracefully.

Example fix

// before
using var image = Image.Load(stream);
// after
try
{
    using var image = Image.Load(stream);
}
catch (InvalidImageContentException ex)
{
    // log ex.Message and treat input as corrupt
}

if (span.Length < 8 || !span.Slice(0, 8).SequenceEqual(new byte[] { 137, 80, 78, 71, 13, 10, 26, 10 }))
    throw new InvalidOperationException("Not a PNG file");

static bool IsPng(Stream s)
{
    Span<byte> sig = stackalloc byte[8];
    return s.Read(sig) == 8 && sig.SequenceEqual(stackalloc byte[] { 137, 80, 78, 71, 13, 10, 26, 10 });
}

try
{
    using var image = Image.Load(stream);
}
catch (InvalidImageContentException ex)
{
    logger.LogWarning(ex, "Rejecting corrupt PNG input");
}

When it happens

Trigger: Any call to Image.Load/LoadAsync, Image.Load<TPixel>, or decoding via PngDecoder where a chunk fails validation and the decoder calls ThrowInvalidImageContentException(errorMessage) with a decoder-specific message.

Common situations: Feeding truncated or hand-edited PNG files, streams containing non-PNG data renamed to .png, files corrupted in transfer, or re-encoded images with spec-violating chunk contents.

Related errors

• Invalid PNG data.
• PNG Image must contain a header chunk and it must be…
• PNG Image does not contain a data chunk.
• {message}
• CRC Error. PNG chunk is corrupt!

AI-assisted analysis of SixLabors/ImageSharp@59ce6af6fc (2026-09-13). Data as JSON: /api/errors/0ae33aff70a41ebb. Report an issue: GitHub.

Appendix: source

Thrown at src/ImageSharp/Formats/Png/PngThrowHelper.cs:12

// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;

namespace SixLabors.ImageSharp.Formats.Png;

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

    [DoesNotReturn]
    public static void ThrowInvalidHeader() => throw new InvalidImageContentException("PNG Image must contain a header chunk and it must be located before any other chunks.");

    [DoesNotReturn]
    public static void ThrowNoData() => throw new InvalidImageContentException("PNG Image does not contain a data chunk.");

    [DoesNotReturn]
    public static void ThrowMissingDefaultData() => throw new InvalidImageContentException("APNG Image does not contain a default data chunk.");

    [DoesNotReturn]
    public static void ThrowInvalidAnimationControl() => throw new InvalidImageContentException("APNG Image must contain a acTL chunk and it must be located before any IDAT and fdAT chunks.");

    [DoesNotReturn]
    public static void ThrowMissingFrameControl() => throw new InvalidImageContentException("One of APNG Image's frames do not have a frame control chunk.");

    [DoesNotReturn]
    public static void ThrowMissingPalette() => throw new InvalidImageContentException("PNG Image does not contain a palette chunk.");

View on GitHub (pinned to 59ce6af6fc)