Remove Color Channels from TIFF Using Command Line

The R function


is used a lot to export R graphics e.g. for publication purposes. The tiff includes all 8 color channels and this collides with formatation requirements of most jounals (1200dpi but not more than some MB in size).

tiff("Whiskerplot.tiff" , width = 8.8 , height = 8.8 , units = "cm" , pointsize = 8 , res = 1200)
produces the required 1200 dpi resolution for monochrome plots, but with all 8 color channels (although just one is necessary) this results in 49.4MB for a tiny 8.8×8.8 cm (ca 3.5×3.5 inch) plot. I used GIMP to remove the color channels with

Image > Mode > Indexed > 1-bit monochrome

but this required opening GiMP, the file, the menu and saving. And again, when the plot had to be modified.

Since this has to be done for each and every publication figure I looked up a command line solution and here it is:
convert Whiskerplot.tiff -flatten -monochrome Whiskerplot_monochrome.tiff
removes all unnecessary colorchannels from Whiskerplot.tiff and saves it as Whiskerplot_monochrome.tiff, reducing the size from 49.4MB to 2.1MB while the result is exactly the same.

Hattip: Paddy Landau on ubuntuforums