BlendMode = enum
  bmNormal, bmDarken, bmMultiply, bmColorBurn, bmLighten, bmScreen,
  bmColorDodge, bmOverlay, bmSoftLight, bmHardLight, bmDifference, bmExclusion,
  bmHue, bmSaturation, bmColor, bmLuminosity, bmMask, ## Special blend mode that is used for masking
  bmOverwrite,              ## Special blend mode that just copies pixels
  bmSubtractMask,           ## Inverse mask
  bmIntersectMask, bmExcludeMask

Blender = proc (backdrop, source: ColorRGBA): ColorRGBA

Masker = proc (backdrop, source: uint8): uint8

BlenderSimd = proc (blackdrop, source: M128i): M128i

MaskerSimd = proc (blackdrop, source: M128i): M128i

proc blendAlpha(backdrop, source: uint8): uint8 {...}{.inline, raises: [], tags: [].}

proc blender(blendMode: BlendMode): Blender {...}{.raises: [], tags: [].}

proc masker(blendMode: BlendMode): Masker {...}{.raises: [PixieError], tags: [].}

proc packAlphaValues(v: M128i): M128i {...}{.inline, raises: [], tags: [].}

proc unpackAlphaValues(v: M128i): M128i {...}{.inline, raises: [], tags: [].}

proc blenderSimd(blendMode: BlendMode): BlenderSimd {...}{.raises: [PixieError],
    tags: [].}

proc hasSimdBlender(blendMode: BlendMode): bool {...}{.raises: [], tags: [].}

proc maskerSimd(blendMode: BlendMode): MaskerSimd {...}{.raises: [PixieError],
    tags: [].}

proc hasSimdMasker(blendMode: BlendMode): bool {...}{.raises: [], tags: [].}