var
	srcx: PRGBTripleArray;
	destx: pbyte;
	y, x: integer;
begin
        //source image assigned to ImageEnView1.IEBitmap....  
	ImageEnView1.io.Params.TIFF_Compression := ioTIFF_LZW;
	ImageEnView1.io.Params.TIFF_PhotometInterpret := ioTIFF_TRANSPMASK ;

	for y := 0 to ImageEnView1.IEBitmap.Height - 1 do
	begin
		srcx := ImageEnView1.IEBitmap.Scanline[y];
		destx := ImageEnView1.IEBitmap.alphachannel.ScanLine[y];
		for x := 0 to ImageEnView1.IEBitmap.Width - 1 do
		begin
		if  (srcx[x].Red   = GetRValue(TranspColor))
		and (srcx[x].Blue  = GetBValue(TranspColor))
		and (srcx[x].Green = GetGValue(TranspColor)) then
			destx[x] := 0
		else
			destx[x] := 255;
		end;
	end;

	ImageEnView1.IEBitmap.SyncAlphaChannel();
	ImageEnView1.Update;
	ImageEnView1.io.SaveToFileTIFF(Filename);
end;

// Save a PNG with alpha to TIFF
ImageEnView1.IO.LoadFromFile( 'D:\Alpha.png' );
ImageEnView1.IEBitmap.PixelFormat             := ie24RGB;
ImageEnView1.IO.Params.TIFF_PhotometInterpret := ioTIFF_RGB;
ImageEnView1.IO.Params.SamplesPerPixel        := 4;
ImageEnView1.IO.Params.BitsPerSample          := 8;
ImageEnView1.IO.Params.TIFF_Compression       := ioTIFF_UNCOMPRESSED;
ImageEnView1.IO.SaveToFile( 'D:\Alpha.TIFF' );