unbearably slow when saving an non-compressed TIFF file using wxtiff

[Ludvik]

I'm trying to  convert .bmp files to tiff type, my basic idea is:

1. Load a .bmp file from storage using wxImage::LoadFile method.
2. Save it on storage using wxImage::SaveFile with wxBITMAP_TYPE_TIF
option.

At first, I got that "LZW not supported" problem.
In order to steer clear of that, I use::
wxImage::SetOption(wxIMAGE_OPTION_COMPRESSION,  COMPRESSION_NONE);
to avoid LZW compression.

Now, .tiff files can be succesfully saved out, but the speed is
unbearably slow: Saving a 1000 * 1000 pixel image could use up to 20
seconds!

Is there ways to improve the saving tiff archive speed??

Millions of thanks in advance...

Ludvik