API Proposal: Update Encoder, EncoderParameterValueType to match GDI+

[qmfrederik]

GDI+ has new values for:

• Encoder: EncoderColorSpace, EncoderImageItems and EncoderSaveAsCMYK
• EncoderParameterValueType: EncoderParameterValueTypePointer

The proposal is to update the Encoder type and EncoderParameterValueType to expose these new values:

namespace System.Drawing
{
    public sealed partial class Encoder
    {
        public static readonly System.Drawing.Imaging.Encoder ChrominanceTable;
        public static readonly System.Drawing.Imaging.Encoder ColorDepth;
        public static readonly System.Drawing.Imaging.Encoder Compression;
        public static readonly System.Drawing.Imaging.Encoder LuminanceTable;
        public static readonly System.Drawing.Imaging.Encoder Quality;
        public static readonly System.Drawing.Imaging.Encoder RenderMethod;
        public static readonly System.Drawing.Imaging.Encoder SaveFlag;
        public static readonly System.Drawing.Imaging.Encoder ScanMethod;
        public static readonly System.Drawing.Imaging.Encoder Transformation;
        public static readonly System.Drawing.Imaging.Encoder Version;
+       public static readonly System.Drawing.Imaging.Encoder ColorSpace;
+       public static readonly System.Drawing.Imaging.Encoder ImageItems;
+       public static readonly System.Drawing.Imaging.Encoder SaveAsCmyk;
        public Encoder(System.Guid guid) { }
        public System.Guid Guid { get { throw null; } }
    }

    public enum EncoderParameterValueType
    {
        ValueTypeByte = 1,
        ValueTypeAscii = 2,
        ValueTypeShort = 3,
        ValueTypeLong = 4,
        ValueTypeRational = 5,
        ValueTypeLongRange = 6,
        ValueTypeUndefined = 7,
        ValueTypeRationalRange = 8,
+       ValueTypePointer = 9,
    }
}

See https://docs.microsoft.com/en-us/windows/win32/gdiplus/-gdiplus-constant-image-encoder-constants, https://docs.microsoft.com/en-us/windows/win32/api/gdiplusenums/ne-gdiplusenums-encoderparametervaluetype

[ViktorHofer]

cc @safern

[safern]

The state that the package is right now this would only be able to be brought to netcoreapp as we harvested the ns2.0/nca2.0/2.1 assets since we did some improvements to use new 3.0 libraries for interop. cc: @JeremyKuhne

[qmfrederik]

I think that's acceptable - users wanting to use these values on earlier versions can do so if they want to:

• The Encoder constructor is public, so anyone can create its own instance of the Encoder class with the correct Guid values
• You could always do EncoderParameterValueType v = (EncoderParameterValueType)9

[terrajobst]

Video

• Looks good as proposed

namespace System.Drawing.Imaging
{
    public sealed partial class Encoder
    {
        // Existing:
        // public static readonly Encoder ChrominanceTable;
        // public static readonly Encoder ColorDepth;
        // public static readonly Encoder Compression;
        // public static readonly Encoder LuminanceTable;
        // public static readonly Encoder Quality;
        // public static readonly Encoder RenderMethod;
        // public static readonly Encoder SaveFlag;
        // public static readonly Encoder ScanMethod;
        // public static readonly Encoder Transformation;
        // public static readonly Encoder Version;
        public static readonly Encoder ColorSpace;
        public static readonly Encoder ImageItems;
        public static readonly Encoder SaveAsCmyk;
    }

    public enum EncoderParameterValueType
    {
        // Existing:
        // ValueTypeByte = 1,
        // ValueTypeAscii = 2,
        // ValueTypeShort = 3,
        // ValueTypeLong = 4,
        // ValueTypeRational = 5,
        // ValueTypeLongRange = 6,
        // ValueTypeUndefined = 7,
        // ValueTypeRationalRange = 8,
        ValueTypePointer = 9,
    }
}