SixLabors/ImageSharp · error · ArgumentOutOfRangeException

Source PCS to target PCS is not supported

Error message

Source PCS {sourceParams.PcsType} to target PCS {targetParams.PcsType} is not supported

What it means

GetTargetPcsWithoutAdjustment (single-value path) switches on the PCS color space recorded in the source profile's ConversionParams; the default arm throws because that combination of source/target PCS types has no implemented conversion route. ICC profiles use either XYZ or CIELab as PCS, and only specific pairs are supported for this intent.

Solutions

Inspect both profiles' header PCS fields (data color space / PCS illuminant signature) and use standard profiles (v2/v4 sRGB, AdobeRGB) whose PCS is XYZ or Lab.
Re-export or fix the offending profile with a standards-compliant tool (e.g. littleCMS, iccMAX).
If you believe the PCS pair should be supported, verify profile version and intent — some pairs are only implemented for perceptual handling.

Example fix

// before
var bad = new IccProfile(); // header PCS unsupported
options.SourceIccProfile = bad;

// after
var options = new ColorConversionOptions
{
    SourceIccProfile = IccProfile.Parse(File.ReadAllBytes("sRGB v4.icc")), // standard XYZ PCS
    TargetIccProfile = target
};

Defensive patterns

Strategy: validation

Validate before calling

IccColorSpaceType pcs = sourceProfile.Header.ColorSpace; // verify PCS field
bool ok = pcs is IccColorSpaceType.CieXyz or IccColorSpaceType.CieLab;

Type guard

bool HasKnownPcs(IccProfile p) => p.Header.ColorSpace is IccColorSpaceType.CieXyz or IccColorSpaceType.CieLab;

Try / catch

try { return converter.ConvertUsingIccProfile<TFrom, TTo>(in color); }
catch (ArgumentOutOfRangeException ex)
{ log.Warn(ex, "Unsupported PCS pair"); return fallbackConversion(color); }

Prevention

Only use profiles from trusted, standards-compliant generators.
Check header PCS signatures when loading profiles.
Prefer bundled standard v2/v4 profiles over third-party or hand-edited ones.

When it happens

Trigger: Calling ConvertUsingIccProfile where the source profile's PCS color space signature (from profile header) is something other than the supported CieXYZ/CieLab cases for the non-perceptual path — e.g. a malformed or exotic profile header, or a PCS pair that falls through all switch cases.

Common situations: Using hand-edited, corrupt, or nonstandard ICC profiles; profiles generated by tools that write unusual PCS signatures; testing with stub profiles.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

AI-assisted analysis of SixLabors/ImageSharp@59ce6af6fc (2026-09-13). Data as JSON: /api/errors/27a43864bff70eb9. Report an issue: GitHub.

Appendix: source

Thrown at src/ImageSharp/ColorProfiles/ColorProfileConverterExtensionsIcc.cs:241

                // if both source and target LUT use same v2 LAB encoding, no need to correct them
                if (sourceParams.Is16BitLutEntry && targetParams.Is16BitLutEntry)
                {
                    CieLab sourceLab = CieLab.FromScaledVector4(sourcePcs);
                    CieLab targetLab = pcsConverter.Convert<CieLab, CieLab>(in sourceLab);
                    return targetLab.ToScaledVector4();
                }
                else
                {
                    sourcePcs = sourceParams.Is16BitLutEntry ? LabV2ToLab(sourcePcs) : sourcePcs;
                    CieLab sourceLab = CieLab.FromScaledVector4(sourcePcs);
                    CieLab targetLab = pcsConverter.Convert<CieLab, CieLab>(in sourceLab);
                    Vector4 targetPcs = targetLab.ToScaledVector4();
                    return targetParams.Is16BitLutEntry ? LabToLabV2(targetPcs) : targetPcs;
                }
            }

            default:
                throw new ArgumentOutOfRangeException($"Source PCS {sourceParams.PcsType} to target PCS {targetParams.PcsType} is not supported");
        }
    }

    private static void GetTargetPcsWithoutAdjustment(
        Span<Vector4> pcs,
        ConversionParams sourceParams,
        ConversionParams targetParams,
        ColorProfileConverter pcsConverter)
    {
        // Profile connecting spaces can only be Lab, XYZ.
        // 16-bit Lab encodings changed from v2 to v4, but 16-bit LUTs always use the legacy encoding regardless of version
        // so ensure that Lab is using the correct encoding when a 16-bit LUT is used
        switch (sourceParams.PcsType)
        {
            // Convert from Lab to XYZ.
            case IccColorSpaceType.CieLab when targetParams.PcsType is IccColorSpaceType.CieXyz:
            {
                if (sourceParams.Is16BitLutEntry)

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