SixLabors/ImageSharp · error · ArgumentOutOfRangeException

Target PCS is not supported

Error message

Target PCS {targetParams.PcsType} is not supported

What it means

In the same perceptual-adjustment path, the target side switch only handles CieLab and CieXYZ; any other target PCS signature reaches the default arm and throws ArgumentOutOfRangeException naming the target profile's PCS type.

Solutions

  1. Check the target profile header's PCS field; re-export the profile so it uses XYZ or Lab PCS.
  2. Swap in a known-good standard profile (sRGB/AdobeRGB) as the target.
  3. Validate profiles at load time with an ICC validator before configuring conversion.

Example fix

// before
options.TargetIccProfile = suspiciousProfile; // PCS field corrupt

// after
options.TargetIccProfile = IccProfile.Parse(File.ReadAllBytes("sRGB.icc"));
Defensive patterns

Strategy: validation

Validate before calling

bool supported = targetProfile.Header.ColorSpace is IccColorSpaceType.CieXyz or IccColorSpaceType.CieLab;
if (!supported) throw new InvalidOperationException("Unsupported target PCS.");

Type guard

bool HasKnownTargetPcs(ConversionParams p) => p.PcsType is IccColorSpaceType.CieXyz or IccColorSpaceType.CieLab;

Try / catch

try { return converter.ConvertUsingIccProfile<TFrom, TTo>(in color); }
catch (ArgumentOutOfRangeException ex) when (ex.Message.Contains("Target PCS"))
{ /* swap target profile */ }

Prevention

When it happens

Trigger: ConvertUsingIccProfile (perceptual intent / v2 adjustment active) where the TARGET profile's PCS color space signature is unsupported.

Common situations: Target profile written by a nonconforming tool; truncated or byte-swapped profile data producing a bogus PCS field.

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/802edc86984b9e24. Report an issue: GitHub.

Appendix: source

Thrown at src/ImageSharp/ColorProfiles/ColorProfileConverterExtensionsIcc.cs:432

            {
                vector = Vector3.Max(vector, Vector3.Zero);
            }

            xyz = new CieXyz(vector);
        }

        switch (targetParams.PcsType)
        {
            // 16-bit Lab encodings changed from v2 to v4, but 16-bit LUTs always use the legacy encoding regardless of version
            // so convert Lab back to legacy encoding before using in a 16-bit LUT
            case IccColorSpaceType.CieLab:
                CieLab lab = pcsConverter.Convert<CieXyz, CieLab>(in xyz);
                Vector4 targetPcs = lab.ToScaledVector4();
                return targetParams.Is16BitLutEntry ? LabToLabV2(targetPcs) : targetPcs;
            case IccColorSpaceType.CieXyz:
                return xyz.ToScaledVector4();
            default:
                throw new ArgumentOutOfRangeException($"Target PCS {targetParams.PcsType} is not supported");
        }
    }

    /// <summary>
    /// Effectively this is <see cref="GetTargetPcsWithoutAdjustment(Span{Vector4}, ConversionParams, ConversionParams, ColorProfileConverter)"/> with an extra step in the middle.
    /// It adjusts PCS by compensating for the black point used for perceptual intent in v2 profiles.
    /// The adjustment needs to be performed in XYZ space, potentially an overhead of 2 more conversions.
    /// Not required if both spaces need V2 correction, since they both have the same understanding of the PCS.
    /// Not compatible with PCS adjustment for absolute intent.
    /// </summary>
    /// <param name="pcs">The PCS values from the source.</param>
    /// <param name="sourceParams">The source profile parameters.</param>
    /// <param name="targetParams">The target profile parameters.</param>
    /// <param name="pcsConverter">The converter to use for the PCS adjustments.</param>
    /// <exception cref="ArgumentOutOfRangeException">Thrown when the source or target PCS is not supported.</exception>
    private static void GetTargetPcsWithPerceptualAdjustment(
        Span<Vector4> pcs,
        ConversionParams sourceParams,

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