SixLabors/ImageSharp · error · InvalidIccProfileException

Unrecognized colorant encoding

Error message

Unrecognized colorant encoding

What it means

IccChromaticityTagDataEntry resolves colorant coordinates only for known colorant encodings (e.g. RGB, CMYK derived from the channel count / colorant type). When the stored colorant value does not map to any known encoding, the entry construction throws InvalidIccProfileException with 'Unrecognized colorant encoding'.

Solutions

  1. Check the colorant encoding/channel count on the source profile; only RGB and CMYK-style chromaticity encodings are supported
  2. Fix or regenerate the profile with a standard tool so the chromaticity tag uses a known encoding
  3. If you only need the raw bytes, read the tag data directly instead of constructing the typed entry
  4. Catch InvalidIccProfileException when loading untrusted profiles and fall back to ignoring the chromaticity tag

Example fix

// before
var entry = new IccChromaticityTagDataEntry((IccColorantEncoding)0x99, channelValues);
// after
if (Enum.IsDefined(typeof(IccColorantEncoding), encoding) && encoding != IccColorantEncoding.Unknown)
{
    var entry = new IccChromaticityTagDataEntry(encoding, channelValues);
}
Defensive patterns

Strategy: try-catch

Validate before calling

bool known = colorant is IccColorantEncoding.Rgb or IccColorantEncoding.Cmy or IccColorantEncoding.Cmyk or IccColorantEncoding.CmykChannel1 or IccColorantEncoding.CmykChannel2 or IccColorantEncoding.CmykChannel3;

Type guard

static bool IsKnownColorant(IccColorantEncoding e) => e is not IccColorantEncoding.Unknown && Enum.IsDefined(e);

Try / catch

try { var entry = new IccChromaticityTagDataEntry(encoding, values); } catch (InvalidIccProfileException ex) { log.Warn(ex, "Unrecognized chromaticity colorant; skipping tag"); }

Prevention

When it happens

Trigger: Constructing an IccChromaticityTagDataEntry (or Equals/GetColorantArray path) with a colorant/channel specification that does not match any supported encoding, e.g. an unexpected ColorantEncoding value combined with a channel count not covered by the switch in GetColorantArray.

Common situations: Loading a malformed or non-standard ICC profile whose chromaticity tag carries an encoding outside the ICC spec subset ImageSharp supports; hand-crafting a chromaticity tag with a wrong channel value.

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/75cc7aad5e2261ee. Report an issue: GitHub.

Appendix: source

Thrown at src/ImageSharp/Metadata/Profiles/ICC/TagDataEntries/IccChromaticityTagDataEntry.cs:143

                    [0.300, 0.600],
                    [0.150, 0.060]
                ];
            case IccColorantEncoding.P22:
                return
                [
                    [0.625, 0.340],
                    [0.280, 0.605],
                    [0.155, 0.070]
                ];
            case IccColorantEncoding.SmpteRp145:
                return
                [
                    [0.630, 0.340],
                    [0.310, 0.595],
                    [0.155, 0.070]
                ];
            default:
                throw new InvalidIccProfileException("Unrecognized colorant encoding");
        }
    }

    private bool EqualsChannelValues(IccChromaticityTagDataEntry entry)
    {
        if (this.ChannelValues.Length != entry.ChannelValues.Length)
        {
            return false;
        }

        for (int i = 0; i < this.ChannelValues.Length; i++)
        {
            if (!this.ChannelValues[i].AsSpan().SequenceEqual(entry.ChannelValues[i]))
            {
                return false;
            }
        }

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