Re: [Gimp-print-devel] Matrix results

[Thomas T. <tt...@bi...>]

Robert L Krawitz wrote:

>    Results: my printer prints darker than yesterday (that was with 3.1.3).
> 
> I presume you updated MATRIX4_SIZE appropriately?

Yes. Actually my first try was the 23x23 matrix, but scaled to a
different maximum values than 23x23. The result was that cyan and black
were printed with very high density, while no yellow or magenta were
printed.

> I noticed that too.  Dark tans did even worse, with nasty green
> splotches.  I don't understand that at all; I would expect ordered
> dither to do very well on such regions, and I certainly wouldn't
> expect splotches.

Maybe it has to do with the way the matrices interleave: only a single
matrix is used. If we would use a different matrix per color, or maybe
nu use 65535-matrixvalue, results would be different.

Green might work well because cyan and magenta use matrixvalue and
65535-matrixvalue. Cyan and black use both matrixvalue - is this matrix
shifted in some place, or rotated perhaps? It could be worthwhile trying
the same matrix for all colors, or use something simple like a shift of
half the matrix width. I'll try that.

> I suggest using 1440 highest quality.  720 softweave is fast, but it
> shows a lot of banding.  We need 720 to work well (and 360, for that
> matter), but for absolute highest quality there's no substitute for
> 1440.

It definitely does bad a little. I was a bit disappointed with 1440, but
that may well have been my choice of dither and not a problem with the
resolution.


Thomas