[comp.os.vms] LN03 Sixel Graphics

PAYNE@ITHACA.BITNET (John Payne) (06/15/87)

Can anyone shed any light on printing sixel format data on an LN03?
The documentation in the LN03 Programmer Reference Manual is unclear,
at least to me.

I need help with the parameters on the device control string that
throws the LN03 into sixel mode.  I would like to get varieties
of grid sizes (dots per inch) while maintaining a 1:1 aspect ratio
(square size pixels).  I was able to get a 1:1 ratio at (roughly)
74 dots per inch using the sequence <ESC>P9;0;0q, but haven't
been able to adjust the parameters for higher resolution square
pixels.

There is also a reference in the manual to a "raster attributes"
control character (DECGRA), which is also unclear to me.

Can anybody help?  Thanks.


John Payne                      Phone:    (607) 274-3704
Academic Computing Services     Bitnet:   PAYNE@ITHACA
Ithaca College                  Internet: PAYNE%ITHACA.BITNET@WISCVM.WISC.EDU
Ithaca, NY  14850

MCGUIRE@GRIN2.BITNET.UUCP (06/18/87)

> Date:         Mon, 15 Jun 87 08:36 EDT
> From:         John Payne <PAYNE%ITHACA.BITNET@WISCVM.WISC.EDU>
> Subject:      LN03 Sixel Graphics
>
> Can anyone shed any light on printing sixel format data on an LN03?
> The documentation in the LN03 Programmer Reference Manual is unclear,
> at least to me.
>
> I need help with the parameters on the device control string that
> throws the LN03 into sixel mode.  I would like to get varieties
> of grid sizes (dots per inch) while maintaining a 1:1 aspect ratio
> (square size pixels).  I was able to get a 1:1 ratio at (roughly)
> 74 dots per inch using the sequence <ESC>P9;0;0q, but haven't
> been able to adjust the parameters for higher resolution square
> pixels.
>
> There is also a reference in the manual to a "raster attributes"
> control character (DECGRA), which is also unclear to me.

If Digital had correctly documented DECGRA, you would not have had a
problem.

In the device control string which selects sixel mode, take the default
ps1 and ps2, and specify the horizontal pixel width in ps3 (in 720/inch
units (decipoints), or, if you use the SSU sequence, 300/inch units
(pixels).

Begin the sixel data with the DECGRA control sequence.  the sequence
defines the aspect ratio of the pixels.  A 2:1 (vertical:horizontal) ratio
causes pixels to be twice as high as they are wide.  The format of the
sequence is not in the manual (EK-OLN03-RM-002, 2nd edition, November
1985).  I arrived at the format by trial and error. Add a note to page 130
of the manual as follows.

   "vertical;horizontal

   Replace `vertical' with the vertical component of the ratio, and
   `horizontal' with the horizontal component.

Finally, here's an example of a sequence that would be imaged using pixels
that are 1/36" in both dimensions.  It assumes that the current size unit
is decipoints.

   <DCS>;;20q"1;1sixeldata<ST>

Good luck!

Ed <MCGUIRE@GRIN2.BITNET>

P.S.  I hope I've got this right.  I never could think very well in
      decipoints!  :-)