ColorPalette:= TIEColorPalette.Create(nil);

ie:= TImageEnView.Create(nil);
//ie.LegacyBitmap:= True;
ie.IO.NativePixelFormat:= True;
//ie.EnableAlphaChannel:= True;
ie.IO.LoadFromFilePng(UniServerModule.EXEDir+'temp\temp.png');

if ie.IEBitmap.PixelFormat <> ie8p then begin
  ie.IEBitmap.PixelFormat:= ie8p; // FAILS TO CHANGE
end;

ColorPalette.AssignPalette(ie, False, True);
ie.IEBitmap.SetTransparentColors(clWhite, clWhite, 0);
ColorPalette.Free;

  // Convert a 32bit PNG file to an 8bit PNG (without transparency)

  ImageEnView1.IO.LoadFromFile( 'D:\Alpha.png');

  // Remove alpha channel and make background white
  ImageEnView1.IEBitmap.RemoveAlphaChannel( True, clWhite );

  // Set PixelFormat to 8bit
  ImageEnView1.IEBitmap.PixelFormat := ie8p;

  // Use PixelFormat as authoritative source of bit-depth
  IEGlobalSettings().AutoSetBitDepth := True;

  ImageEnView1.IO.SaveToFile('D:\No-Alpha.png');