Currently TIFFSEP can only create CMYK Separte TIFFs in grayscale , can't create 1 bit/sample CMYK Separate TIFFs.event with the -dBitsPerSample=1 setting.
This is probably not very difficult, but I recommend that, for consistency with the 'bit***' devices and the ppmraw devices, the -dGrayValues= value be used. While some devices described in 'doc/Devices.htm' use BitsPerSample and BitsPerPixel, it would be better to stick to -dGrayValues= since this is described in doc/Use.htm, which is a more general document, and is more likely to be "discovered" by users. For a bounty solution, I'd like to see the documentation in doc/Devices.htm for the tiffsep device as well as improved documentation in the doc/Use.htm section. Note that in the meantime, programs such as ImageMagick 'convert' can be used in a separate step to dither the gray images down to 1-bit per pixel. For example, convert bits-8.tif -ordered-dither o8x8 -depth 1 bits-1.tif
Currently is there any way to create CMYK Separate mono TIFF files? I tried -dGrayValues BitsPerPixel and -BitsPerSample. all dosen't work, I also tried to set Dithering Type as gsmono. No help either. So currently for TIFF* device, no paramter can change the sample depth. Is that correct?
I created the 'tiffsep1' device that creates 1-bit per pixel separations, including CMYK and any named separations. I recommend rev 10394 or later (that's the most recent change specific to tiffsep1).