discrete color scale bitmap becomes continuous object after eps/pdf export

It seems to me that Inkscape's cairo-based export is correctly interpreting the SVG data based on the SVG specification:

If adding the missing attribute mentioned in bug #616717 to the <image> element, the scaled bitmap image renders equally as continuous color scale in other SVG viewers (Batik, Firefox, Opera, librsvg) as it appears in cairo-based exports from Inkscape (PDF as well as PostScript).

Inkscape's current trunk though renders the scaled bitmap rather blurry towards all edges (unlike other SVG viewers).

Related earlier reports:
- Bug #461467 in Inkscape: “Image scale saved incorrectly”
- Bug #616717 “Resized bitmap images are rendered differently by Firefox or Batik ('preserveAspectRatio' attribute not set)”
and
- Bug #1163449 “Imported bitmap appear blurry when zoomed in”
(new rendering of scaled bitmap images in current Inkscape trunk: it appears that Inkscape's pixelized view of up-scaled / zoomed-in bitmap images (old renderer in stable versions, trunk <= r12227) does not conform to the current SVG 1.1 specification, and that the spec currently does lack a solution supported by Inkscape to produce the same view as produced by Inkscape's old renderer in current stable versions)

Disucssion on 'inkscape-devel' related to rendering of up-scaled bitmap images:
<http://article.gmane.org/gmane.comp.graphics.inkscape.devel/40188>

Various screenshots (SVG: librsvg 2.36.3, Squiggle (Batik 1.7), Opera 12; EPS: evince 2.30.3, cairo 1.12.2)

I tried to reproduce the results using an older version of inkscape.
With inkscape 0.47 on debian squezze I get a discrete color scape in the eps.

There is no one correct way to interpolate a bitmap, and SVG lacks a way of defining what interpolation to use. (As mentioned above, we recently had a discussion on this subject.) PDF apparently does have a switch to control interpolation to some degree (I am not sure about eps, but it might have one as well), so if Inkscape did have a way to at least switch between "blocky" and "smooth", then we could look into making sure that this gets transferred correctly to/from pdf (and possibly eps). In that light I would consider this report to essentially constitute a feature request (one that at the moment, unfortunately, cannot be adressed just yet).

On 2013-05-01 10:03 (+0200), Jaspervdg wrote:
> if Inkscape did have a way to at least switch between "blocky" and
> "smooth", (...)

Implemented in Inkscape 0.91 (on import, and changeable later on via
Object properties dialog).

> (...) then we could look into making sure that this gets transferred
> correctly to/from pdf

Export: supported with Inkscape 0.91 r13725
(see attached examples: SVG, PDF, screenshot Evince)

Import: Implemented for upcoming 0.92, see revision 14171:
* Respect PDF image 'interpolate' value on import.
https://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/14171