FAX conversion results in reversing black on white images

[terrapinsail]

I have a Group4 TIFF that I need to convert to a Group3 FAX. The command convert -compress fax tifg4.tif tifg3.tif , results in an image where the background is black and the text is white. Any idea why this is happening and/or a modification to the command line above to correctly convert the image without changing the black and white pages? thanks.

[fmw42]

I don't know much about Tiff faxes, but a workaround might be

convert -compress fax tifg4.tif -negate tifg3.tif

or

convert tifg4.tif -compress fax -negate tifg3.tif

[terrapinsail]

Thanks that sorta worked. The document is a multipage tif with one color page. Using the command 'convert -compress fax tif1.tif tif2.tif results in all b/w pages turning to white on black and the color page looking like the source page (just fine). Taking your recommendation and running 'convert -compress fax tif1.tif -negate tif2.tif, retains the black on white for the b/w pages, but it reverses the color on the color page! help

[fmw42]

separate the pages/frames, process only the b/w white with -negate, then recombine.

convert image.tif image_%d.tif

will separate them.

Then process the non-color ones

convert image_01.tif -negate image_01.tif
convert image_02.tif -negate image_02.tif
etc

Then recombine all the frames

convert image_01.tif .... image_0n.tif image_new.tif