You could use Document Express Enterprise at the command line, specify "agressive" there for text cleanup, and then your results should be similar. To answer your question about bitonal compression, when you use "clean" in DjVu Libre, the "text quality / text cleanup" setting is "agressive", while in Document Express (Enterprise 5.0), when you use "DocumenttoDjVu", this is just a placeholder name for the "Scan300" profile, in which the "text quality /text cleanup" setting is hard-coded to "normal". Then the size should be similar, not smaller. Of course, you can select a "Photo" profile in Document Express and then segmentation will not occur - the image will only be IW44-compressed. This will result in a significantly smaller file than one produced by DjVu Libre without segmentation. The segmenter splits the color image into color and bitonal planes, and only the background color plane gets the IW44 compression, while the foreground bitonal layer gets JB2 compression. For color images, both DjVu Libre and Document Express are based on the IW44 algorhithm, it is true, but Document Express has an image segmenter that DjVu Libre does not have.
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