PeachImage
PeachImage.Formats.Png.PngEncoderOptions
PngEncoderOptions.ColorMode Property
Controls whether the encoder builds an indexed (PLTE, color type 3) palette instead of grayscale/ truecolor. Default Auto. Ignored (and indexed encoding skipped) whenever TransparentColor is set, since color-key transparency and a quantized palette target different scenarios and combining them isn’t supported.
public PeachImage.Formats.Png.PngColorMode ColorMode { get; init; }