Re: [Bug 688243] Spurious lines between joined filled rectangles and antialiasing (fwd)

[Daniel J S. <dan...@ie...>]

Robert Hart wrote:
> On Thu, 2005-07-28 at 11:02 -0500, Daniel J Sebald wrote:
> 

<snip>

> Presumeably what we are seeing is some kind of rounding error, where our
> two adjoining polygons don't lead to a final alpha value of one. By
> having a positive thickness to the lines around the objects, they
> effectively overlap (albeit slightly) and hence are more likely to get
> it right.

Oh, I see.  That might also explain the odd polygon colors I used to see.

Actually, I just found that the problem hasn't gone away with the software in Fedora 3.  It is obviously much better so perhaps there were multiple issues.

Anyway, I'm using GhostView right now to view one of Petr's b/w sinc-like, 2D-projected, grayscale images.  There are lines; but turning off antialiasing from the "State" menu causes the lines to go away.  (Of course, this demo example doesn't have high enough spatial frequency to cause aliasing.)  The color bar also looks much better.  (No aliasing possible there in monochrome, unless intentional.)

> An alternative approach, which may produce better results, is to rended
> the image at a higher resolution, and then reduce the resolution. This
> may not necessarily need more memory, as the image could be split into
> smaller tiles, but that is getting off topic.

That's on topic.  

> I think the situation is slightly better for the X11 driver, because the
> resolution of the output device is known in advance, you can therefore
> round coordinates to get better results. (I think ghostscript
> antialiased images can look quite blurry especially for vertical and
> horizontal lines)

Perhaps.

Dan