Re: High res Colour Printing in RISC OS 3.1

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2 total messages Started by /G=Owen/S=Smith/O=SJ-Research/AD... Fri, 18 Dec 1992 14:59

#696

Author: /G=Owen/S=Smith/O=SJ-Research/AD...
Date: Fri, 18 Dec 1992 14:59

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maupb@csv.warwick.ac.uk (Mr J L Saunders) wrote:

(In reply to my stuff about not doing interlaced colour dot matrix
printing.)

>Why not just print the yellow first? This seems obvious to me.

Indeed for horizontal interlacing this is actually what happens. I realised
this while writing the technical documentation for the PRM. So 360 by 180
would be safe, but it'll probably still look bad because 8 head passes is
over the top. Anyway 180 by 180 on a 24 pin printer is fine, what isn't is
120 by 72 on an 8 pin printer, which is the maximum resolution without
interlacing. 240 by 72 would also be feasible, but what you really want is
120 by 144 which is vertically interlaced and so the yellow would overprint
on dark colours. To print the yellow first, you'd need to reverse feed the
paper by 1/216". A lot of printers don't support reverse paper feed at all,
and those that do tend to do it inacurrately. The sequence would be:

Yellow pass, forward paper feed 1/216 inch
Yellow pass, reverse paper feed 1/216 inch
Cyan pass, forward paper feed 1/216 inch
Cyan pass, reverse paper feed 1/216 inch
Magenta pass, forward paper feed 1/216 inch
Magenta pass, reverse paper feed 1/216 inch
Black pass, forward paper feed 1/216 inch
Black pass, forward paper feed 23/216 inch

Any bets on whether the paper will still be remotely close to where it ought
to be after this sequence? Whiplash and mechanical tolerances may well mean
that the reverse feeds do nothing at all and just take up the slack in the
gearing instead. Many of the newest dot matrix printer models have removed
support for the reverse paper feed command completely or have written DO NOT
USE in big letters in the manual. So using it does not seem like a good
idea.

Owen.

Re: High res Colour Printing in RISC OS 3.1

#508

Author: blacka
Date: Mon, 21 Dec 1992 23:41

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As the instigator of this discussion, I would like to thank
everyone who's replied to it.  It has been an interesting
discussion, and I have learnt a lot about the subject.
I have  sucessfully set up the control codes for 360x180 
colour printing.  I accept that it takes a long time and
only use if when I feel it is needed.

A couple of points remain however :

- Owen is concerned about the ribbon becoming dirty 
  because of overprinting.  I would guess this is only a 
  problem with Y-interlace - for X interlace the driver
  does the two yellow passes, etc ending with black.  Am
  I correct here.

- I am confused as to whether and XB24 printer really prints
  to   360 resolution (or whether it skips a dot immediately
  after another dot).

  My XB24 manual is contradictory on this point.   In the 
  table of control codes (p58 if anyone has a copy) it 
  gives the impression that you can print every dot, whereas
  the spec on page 106 claims "Adjacacent dots not printable
  in these modes".   I suspect the latter is the case - 
  does anyone have any hard evidence.

Final point - I have noticed that the quality of Outline
Font printout is better under RISCOS3.1 than 2.  Previously
I found 180x180 was poor, 360x360 was needed.  Now I  find
that 180x180 is acceptable, and 360x180 when I need high
quality.  Could Owen shed any light on what has  be done
to obtain this  improvent 


Andrew Black

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