Scanning Suggestions (Bookmarks & Colour)

Antonio Carlini a.carlini at
Fri Sep 3 04:10:50 CDT 2021

On 02/09/2021 20:51, Paul Flo Williams via cctalk wrote:
> With apologies for breaking the threading, as I've just rejoined and I'm
> responding to something I've just spotted in the archive ...

Welcome back!

> I haven't finished writing this up, but my workflow tends to be to
> produce a Group4 TIFF from the colour scan by simple thresholding (or
> first dropping the other colours to white, if they are quite dark), and
> then produce all the other separations by dropping black out,
> converting your spot colour to black and then thresholding. This way
> you get two or more images:
> 1) PNG(s) containing pixels that are all either white or your spot
> colour,
> 2) a G4 TIFF for the black and white layer.

As I'm in the process of scanning manuals right now, and I'd like to 
preserve the colour, I'm looking forward to the write up.

The ones I'm working on right now are mostly RSX-11 or VMS V4 and 
earlier, so they tend to highlight typed input by presenting that text 
in red.

They also have blocks of grey as background on which text is printed 
(this looks OK even with a bilevel TIFF) and also blocks of red/pink as 

for black text (and maybe red text too). I'm sure there's at least one 
manual that has blue text thrown into the mix too.

> I've just scanned another document with some blue diagrams and table
> backgrounds, if you'd like to see an example:
That looks really good. It copes very well with black text on blue 
background, so I imagine it would work well for the black text on 
red/pink shading case.

What's the input to the process? G4 bilevel TIFF @ 600 dpi from the 
looks of your example, but how do you scan the colour pages? 600dpi to 
PNG? Or something else?



Antonio Carlini
antonio at

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