Re: Image size, DPI (was Re: Gorm is broken)

[Fred Kiefer]

On 09.05.2011 22:01, Eric Wasylishen wrote:
> On 2011-05-08, at 12:47 AM, Fred Kiefer wrote:
>
> > -------- Original-Nachricht --------
> > > Datum: Sun, 08 May 2011 01:32:58 +0200 Von: Riccardo
> > > Mottola<address@hidden> An: Eric
> > > Wasylishen<address@hidden> CC: Developer
> > > GNUstep<address@hidden> Betreff: Re: Image size, DPI (was
> > > Re: Gorm is broken)
> >
> > > Hi,
> > > > On a related note, I think the Cairo backend also rounds the
> > > > coordinates
> > > of path points - shouldn't we get rid of that as well?
> > > >
> > > I think that perhaps we should. But it is a delicate issue. Try
> > > Graphos:play with it drawing boxes and lines especially, check
> > > our various backends and check cocoa. Try different line widths.
> > > My impression is that on cairo everything is always blurred :)
> > > Xlib of course never since it has no anti-aliasing. But Cocoa
> > > isn't as "bad" as cairo, it usually looks fine for integer line
> > > widths.
> >
> > If I remember correctly the code here tries to avoid bluring for
> > lines that the programmer would expect to be exactly horizontal or
> > vertical oriented. This is the standard approach used by all cairo
> > applications I know of. We should add a lot of tests before we
> > change this.
>
> Ok. I agreed it should be well tested if changed. Based on a quick
> check, however, cairo's and Cocoa's default behaviour are exactly the
> same , i.e. the examples here:
> http://www.cairographics.org/FAQ/#sharp_lines produce the same
> results on Cocoa, so it doesn't appear that cocoa does any rounding
> below the level of NSView implementations.

Are you saying that Cocoa basic drawing operations have the same blur 
effect for horizontal single pixel lines? Does this affect only the 
CoreGraphics functions or also the NSBezierPath methods? And what about 
the still supported PS functions?
If this is the case we need to move the half pixel correction up one 
level into gui. I remember that before that correction was added use 
interface elements with the cairo backend looked less sharp.