Re: resolution independent px

Hi,

On Sun, Jan 18, 2015 at 09:20:06PM +1300, James C wrote:
> Hi Johannes,
> 
> Reading the link, it looks like normally viewed displays with any
> resolution between about 50 DPI and 140 DPI will have one CSS pixel
> exactly equal to one device pixel; so resolutions outside that are the
> definition of 'differs a lot' in the standard.
> 
> What's the overhead of asking the library to re-scale the image to the
> size that it already is?  If it's significant, then maybe there needs
> to be a special case for 1:1.

the overhead is significant in case images would not be scaled
otherwise, so we would want to special case it somehow.

> 
> I start out with a bias against adding another run-time option, but
> it's based on my not-very-relevant experience of adding an option to
> dpid.
> 
> Contradicting myself, the standard implies that there could be an
> option for viewing distance, in which case there could be a special
> case to that option for 'never scale'.

As nobody actually has a problem at the moment I think we can
postpone this. It will come up again as high resolution devices are
becoming more popular.

Cheers,
Johannes

> 
> Regards.
> James.
> 
> On 1/18/15, Johannes Hofmann <[email protected]> wrote:
> > On Fri, Jan 16, 2015 at 12:14:19PM -0300, Jorge Arellano Cid wrote:
> >> On Fri, Jan 16, 2015 at 08:50:13AM +0100, Johannes Hofmann wrote:
> >> > Hi,
> >> >
> >> > attached is a patch that would enable resolution independent
> >> > handling of px as described in [1].
> >> > It would result in roughly equally sized images on high and low
> >> > resolution devices at the cost of a higher overhead for additional
> >> > image scaling.
> >>
> >>   A long time ago, image scaling was relatively low overhead,
> >> but since dillo got correct gamma correction, it became much
> >> more expensive.
> >>
> >>   I remember testing this and the difference was noticeable.
> >> It was left anyway because the amount of scaled images
> >> in the average web page is low.
> >>
> >>
> >> > Is there a need for something like this?
> >>
> >>   I don't know...
> >>
> >> > Should it be enabled via config option or should we do it
> >> > automatically if we detect a DPI value that differs a lot from
> >> > the standard value?
> >>
> >>   For me, it is hard to say without knowing the main use of it.
> >> What I do know is that our scaling is CPU intensive, so I tend
> >> to have it off unless necessary.
> >
> > It's only useful if you have a high resolution device where DPI is
> > much higher than about 70. In that case images will be rendered
> > very small.
> >
> > I currently don't have such a device, so personally I don't have
> > any need for this now. I just wanted to get feedback from dillo-dev
> > in case someone already ran into this issue.
> >
> > Cheers,
> > Johannes
> >
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> >
> 
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