SixLabors/ImageSharp · error · InvalidImageContentException

Bad sampling factor.

Error message

Bad sampling factor.

What it means

JpegThrowHelper.ThrowBadSampling throws InvalidImageContentException when a frame's component sampling factors are invalid — each component's horizontal/vertical sampling factor must be in 1..4 per the JPEG spec. The parameterless overload reports a generic bad sampling factor.

Solutions

1. Re-obtain or re-export the image; the file header is non-conformant.
2. Catch InvalidImageContentException and skip/quarantine in batch processing.
3. If you control the producer, fix the encoder so sampling factors are within 1..4.

Example fix

// before
using var image = Image.Load(input);
// after
try { using var image = Image.Load(input); }
catch (InvalidImageContentException ex)
{
    quarantine(ex, inputPath); // bad sampling factors in SOF
}

try
{
    using var image = Image.Load(stream);
}
catch (InvalidImageContentException ex) when (ex.Message.Contains("sampling"))
{
    quarantine(stream, "Bad sampling factors in SOF");
}

When it happens

Trigger: Decoding a JPEG whose SOF0/SOF2 segment declares a component sampling factor of 0 or greater than 4 (the message shows the offending factor in the int overload) — corrupt headers or non-conformant encoder output.

Common situations: Files from broken camera/embedded encoders; bit corruption; fuzzed or malicious uploads; truncated header bytes shifting parsing.

Related errors

• Marker has bad length .
• Bad Quantization Table index
• Unknown Quantization Table precision
• {errorMessage}
• Input stream does not have enough bytes to parse declared…

AI-assisted analysis of SixLabors/ImageSharp@59ce6af6fc (2026-09-13). Data as JSON: /api/errors/9dcd692b5a3d05c3. Report an issue: GitHub.

Appendix: source

Thrown at src/ImageSharp/Formats/Jpeg/JpegThrowHelper.cs:20

// Licensed under the Six Labors Split License.

namespace SixLabors.ImageSharp.Formats.Jpeg;

internal static class JpegThrowHelper
{
    public static void ThrowNotSupportedException(string errorMessage) => throw new NotSupportedException(errorMessage);

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

    public static void ThrowBadMarker(string marker, int length) => throw new InvalidImageContentException($"Marker {marker} has bad length {length}.");

    public static void ThrowNotEnoughBytesForMarker(byte marker) => throw new InvalidImageContentException($"Input stream does not have enough bytes to parse declared contents of the {marker:X2} marker.");

    public static void ThrowBadQuantizationTableIndex(int index) => throw new InvalidImageContentException($"Bad Quantization Table index {index}.");

    public static void ThrowBadQuantizationTablePrecision(int precision) => throw new InvalidImageContentException($"Unknown Quantization Table precision {precision}.");

    public static void ThrowBadSampling() => throw new InvalidImageContentException("Bad sampling factor.");

    public static void ThrowBadSampling(int factor) => throw new InvalidImageContentException($"Bad sampling factor: {factor}");

    public static void ThrowBadProgressiveScan(int ss, int se, int ah, int al) => throw new InvalidImageContentException($"Invalid progressive parameters Ss={ss} Se={se} Ah={ah} Al={al}.");

    public static void ThrowInvalidImageDimensions(int width, int height) => throw new InvalidImageContentException($"Invalid image dimensions: {width}x{height}.");

    public static void ThrowDimensionsTooLarge(int width, int height) => throw new ImageFormatException($"Image is too large to encode at {width}x{height} for JPEG format.");

    public static void ThrowNotSupportedComponentCount(int componentCount) => throw new NotSupportedException($"Images with {componentCount} components are not supported.");

    public static void ThrowNotSupportedColorSpace() => throw new NotSupportedException("Image color space could not be deduced.");
}

View on GitHub (pinned to 59ce6af6fc)