dotnet/wpf · error · InvalidOperationException

Image_EncoderNoColorContext

Error message

Image_EncoderNoColorContext

What it means

The BitmapEncoder.ColorContexts setter rejects values when the encoder's codec does not support color contexts (_supportsColorContext is false), throwing InvalidOperationException(Image_EncoderNoColorContext). Most built-in codecs support this, but codecs lacking global color-context support cannot accept it.

Solutions

1. Only set ColorContexts when encoder.CodecInfo supports color contexts
2. Switch to a codec that supports color contexts (Png, Tiff, Jpeg, Wmp)
3. Guard the assignment with a capability check derived from CodecInfo.DeviceManufacturer/Format capabilities
4. Remove the ColorContexts assignment for unsupported formats

Example fix

// before
encoder.ColorContexts = sourceFrame.ColorContexts; // throws for Bmp
// after
if (encoder.CodecInfo != null && encoder is TiffBitmapEncoder || encoder is PngBitmapEncoder)
{
    encoder.ColorContexts = sourceFrame.ColorContexts;
}

if (encoder is BmpBitmapEncoder) throw new NotSupportedException("Bmp encoder does not support color contexts");

static bool SupportsColorContexts(BitmapEncoder e) => e is not BmpBitmapEncoder; // codecs w/o context support

try { encoder.ColorContexts = contexts; }
catch (InvalidOperationException) { // codec has no color-context support
    // proceed without embedding color contexts
}

When it happens

Trigger: Setting encoder.ColorContexts = [...] on a BitmapEncoder whose underlying container/codec does not support color contexts (checked in the setter after EnsureBuiltIn and a null check).

Common situations: Using BitmapEncoder.Create with a third-party or limited codec GUID, or copying metadata/color contexts between formats whose encoders have different capabilities (e.g. Bmp vs Tiff/Png).

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Image_EncoderNoGlobalMetadata
• Image_EncoderNoGlobalThumbnail
• Image_EncoderNoPreview
• Image_OnlyOneSave
• SR.Color_NullColorContext

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/b35ad68636065ee9. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Imaging/BitmapEncoder.cs:134

        /// </summary>
        public virtual ReadOnlyCollection<ColorContext> ColorContexts
        {
            get
            {
                VerifyAccess();
                EnsureBuiltIn();
                return _readOnlycolorContexts;
            }
            set
            {
                VerifyAccess();
                EnsureBuiltIn();

                ArgumentNullException.ThrowIfNull(value);

                if (!_supportsColorContext)
                {
                    throw new InvalidOperationException(SR.Image_EncoderNoColorContext);
                }

                _readOnlycolorContexts = value;
            }
        }

        /// <summary>
        /// Set or get the bitmap's global embedded thumbnail.
        /// </summary>
        public virtual BitmapSource Thumbnail
        {
            get
            {
                VerifyAccess();
                EnsureBuiltIn();
                return _thumbnail;
            }
            set

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