Re: [AGG] Subpixel problem - 90/180 deg. lines

[Oyvind I. <oyv...@gm...>]

Thing is, the ordinates are already piped through other converters, such as
parallel shifting (in some cases), conv_transform (always), etc.
I have objects in one coordinate-system affined into pixel-space
coordinates.

Making a conv_transform etc. aware of pixel adjustment, sounds quite
complicated, not to mention a heck lots of work ?

Correct me if I misunderstand you.


-- Oyvind


On Mon, Mar 7, 2011 at 9:32 PM, Ben Harper <be...@im...> wrote:

> I think it's the wrong approach to use rounding to fix that. A (0.5,0.5)
> translation converter is better, since you can then mix and match integer
> and non-integer coordinates. Even better is if your entire pipeline is aware
> of the pixel coordinate system, and you apply the layout rounding at the
> appropriately higher level (perhaps at design time). WPF et al have their
> 'Layout Rounding' property that you can set on UI objects - I don't know
> exactly at what stage of the pipeline that gets applied.. all I'm really
> saying is that it's probably better that you understand the problem fully
> and apply the correction to the right place of whatever stack it is you're
> building.
>
> Ben
> ________________________________
> From: Oyvind Idland [oyv...@gm...]
> Sent: Monday, March 07, 2011 6:12 PM
> To: Anti-Grain Geometry
> Cc: Phil Endecott
> Subject: Re: [AGG] Subpixel problem - 90/180 deg. lines
>
> Yep, thats the problem.
>
> I think I'll make a new conv_round() class and wrap it up that way in those
> cases.
>
>
> -- Oyvind
>
> On Mon, Mar 7, 2011 at 3:58 PM, Phil Endecott <spa...@ch...
> <mailto:spa...@ch...>> wrote:
> Oyvind Idland wrote:
> > When a line segment is 90 or 180 degrees (has same x or y), the subpixel
> > logic makes the lines appear as 50% transparent and twice as fat as they
> > should be.
>
> Presumably that is the standard issue of whether 1-px-wide lines are
> better centred on whole coordinates or on 0.5 coordinates, i.e. are
> "pixels" points or unit-squares.
>
>
> Phil.
>
>
>
>
>
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