Re: [Gimp-print-devel] Epson Stylus Photo 1270 Paper Margins with 3.1.4.

[Ralph C. <ra...@in...>]

Hi,

> > I print crosses at certain points on the page;  two lines, one
> > horizontal, one vertical.  At some locations the horizontal line
> > fails to appear *completely*.  This suggests some horizontal rows
> > are being missed.  Similarly, the diagonal line has many small
> > gaps.  It's as if drawn with a very long, erratic, dash pattern,
> > again suggesting some horizontal rows are being missed.
> 
> I think I understand.  I suggested using -r1440.  This means that
> Ghostscript uses both a horizontal and vertical resolution of 1440
> dpi.  However, quality=7 is only 720 dpi vertically, so every other
> horizontal row will be missed.
> 
> Two things to try:
> 
> 1) Use -r720.  This will do 720 dpi in Ghostscript.

That works well.  All lines are solid.  The lines that are solid on
both the 1440 and 720 print outs appear to be the same thickness.  The
diagonal line appears to have the slightest of gaps occasionally.

I tried -r1440x720, since that's the printer's resolution.  I the same
image as before, still with some horizontal lines missing, but squashed
vertically so it only filled the top half of the A4 page.  Was I stupid
to try this?  :-)

> 2) Use -dQuality=8.  This mode, called "1440x720 enhanced", actually
> samples at 1440x1440.

That was an improvement in some ways.  With -r1440 all the missing
horizontal lines have now appeared.  But, all lines, horizontal,
vertical, and diagonal are still `dashy' where as the vertical lines
appeared solid with -dQuality=7.

> > I'd guess that this is because the PostScript is drawing lines with
> > a line width of zero;  defined to be the thinnest line width the
> > output device supports.  Perhaps the stp driver is over estimating
> > how thin this line can be?
> 
> It isn't the stp driver; it doesn't know anything about Postscript or
> line widths.

OK.  Perhaps the various dithering methods don't work well on very thin
lines?


Ralph.