Bug#596774: iceweasel: upscaled images looks ugly

[Mike Hommey]

On Mon, Sep 13, 2010 at 05:58:07PM -0500, evgeny wrote:
> Package: iceweasel
> Version: 3.5.12-2
> Severity: normal
> Tags: patch
> 
> Upscaled images looks ugly. Here is what is written about it in
> /iceweasel-3.5.12/gfx/src/thebes/nsThebesImage.cpp line 672:
> 
> // See bug 324698.  This is a workaround for EXTEND_PAD not being
> // implemented correctly on linux in the X server.
> //
> // Set the filter to CAIRO_FILTER_FAST --- otherwise,
> // pixman's sampling will sample transparency for the outside edges
> // and we'll
> // get blurry edges.  CAIRO_EXTEND_PAD would also work here, if
> // available
> //
> // But don't do this for simple downscales because it's horrible.
> // Downscaling means that device-space coordinates are
> // scaled *up* to find the image pixel coordinates.
> //
> // deviceToImage is slightly stale because up above we may
> // have adjusted the pattern's matrix ... but the adjustment
> // is only a translation so the scale factors in deviceToImage
> // are still valid.
> 
> This workaround  makes upscaled images look really  bad, but it is not
> needed anymore! For quite long  time everything works fine without it,
> i.e. X  server was fixed I  guess. I've been patching  (disabling this
> workaround)  and building  iceweasel  myself for  quite sometime,  and
> images look way  better. So please include this patch!  Just got tired
> building iceweasel myself. Many users  like me with high resolution of
> the screen need to scale web-pages, but then in the current version of
> iceweasel/firefox images looks really ugly.

The upstream fix suggests this only really works well with cairo >=
1.9.2. With earlier versions, it doesn't use XRender, which would make
it slow and CPU sucky.

Mike