[Pixman] [PATCH 07/15] pixman-filter: Speed up the BOX+BOX filter

Bill Spitzak spitzak at gmail.com
Mon Jan 11 09:33:41 PST 2016

Yes I will try to send new versions asap.

Known mistakes/problems:

1. I was a bit too fast at deleting the recursion code for the linear
filters. The problems were not very visible with the 16-segment simpsons
integration, but obvious when reducing to 4 (which otherwise works in most
cases). Also it is actually easier to split with my new arguments to the
function, so I really should not have done that.

2. x.LINEAR where x is not IMPULSE or BOX or LINEAR is producing artefacts
that don't seem to exist in other combinations (or are much less visible in
other combinations?). I think I need to investigate this.

3. My comment is somewhat inaccurate and I need to update it. LINEAR.LINEAR
is only a cubic at scale==1, it is not possible to replicate what other
software calls "cubic" or "bicubic" using this

On Mon, Jan 11, 2016 at 1:16 AM, Oded Gabbay <oded.gabbay at gmail.com> wrote:

> On Fri, Jan 8, 2016 at 8:53 PM, Bill Spitzak <spitzak at gmail.com> wrote:
> >
> >
> > On Thu, Jan 7, 2016 at 11:44 PM, Pekka Paalanen <ppaalanen at gmail.com>
> wrote:
> >>
> >>
> >> Please keep in mind that the filters GOOD and BEST have been as is for
> >> a long long time, AFAIU, so changing their behaviour now is likely not
> >> a good idea. They are no longer "a good filter" and "whatever best
> >> filter", but "the specific filter called GOOD" and "the specific filter
> >> called BEST", in lack of documentation saying otherwise.
> >
> >
> > Both GOOD and BEST are identical to BILINEAR in the current version of
> > Pixman. Therefore anybody relying on the current behaviour can achieve
> it by
> > using BILINEAR. In addition GOOD is unchanged for any scales larger than
> .75
> > or for a scale of exactly .5.
> >
> > Also despite their names, bilinear in no way would be considered "good"
> or
> > "best" by any sane person. We should not add illogical names (like
> > or whatever) just because of paranoia over back-compatibility. It is also
> > highly desirable that the default actually be "good", this cannot be done
> > unless GOOD is changed, or the default is changed to "NEW_GOOD".
> >
> > This change was made to Cairo over a year ago with no complaints (except
> for
> > speed issues, which this patch is necessary to solve by moving the fix
> from
> > Cairo to Pixman). Lets get out of the dark ages, and stop doing things
> that
> > are making open source desktops a laughingstock.
> >
> Hi Bill,
> I just now read the new emails (I was on PTO for the last week).
> It seems you found some mistakes and you want to resend a new version.
> Did I understand you correctly ?
> If that is indeed the case, then I prefer to wait for that version
> (v9), and skip reviewing v8.
> Please ack this.
> Oded
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