How to Stop Source Formatting

I want to track whether the content is modified by user or not, so I need to compare the string passed to fckeditor with the new value from fckeditor. But I see fckeditor will always format the input text, so the compare result is always changed even the user does not make any changes.

for example, I give fckeditor the input:

When I go the 'Source' page, I get:
<p><img alt="" width="120" height="168" src="/img/67108865_001.bmp" /></p>

I already tried these 2 config, but seems no effect.
FCKConfig.FormatSource = false ;
FCKConfig.FormatOutput = false ;

Is there any solution or workaround?