> On Mar 20, 2018, at 7:50 AM, Mattis Lind via cctalk <cctalk@classiccmp.org>
> wrote:
>
> So I have imaged the three disks I found using ImageDisk:
> http://storage.datormuseum.se/u/96935524/Datormusuem/TEXAS.zip
>
> Then I scanned one of the manuals. UCSD Pascal :
> http://storage.datormuseum.se/u/96935524/Datormusuem/UCSD-Pascal.pdf
>
> The problem is that manual has text in red/brown and black. I scanned it in
> colour. However the actual colour of the scan varies a bit between pages.
> (Maybe because there are two sensors, one for top side and one for bottom
> side.)
> And the scan get very big.
>
> Is there a way to create filter this pdf to use three colours and possibly
> compress it better? What is the best way to deal with scans of documents
> with coloured text. I know many DEC manuals that has coloured text as well.
Yes, you can do that with photo editing programs, which often have scripting
("batch processing") features so you can do it repeatedly. Depending on the
quality of the source material it may be hard to get right, though.
One technique that's useful in dealing with colors in the way you want to is to
convert the images to "Lab" (or "L*a*b") format, as opposed to RGB or CMYK.
That separates the brightness information from the red/green and yellow/blue
distinctions, and lets you apply curves, or threshold operations, or things
like that to emphasize colors or force them to particular values. It will take
experimenting with your particular source material to figure out the way.
If standard programs don't do the job, an image file manipulation library might
be the way to get at this.
paul
