Re: Down sampling guidance for raster content in SVG.

> Inkscape implements 'image-rendering' with the SVG 1.1 values 'auto',
> 'optimizeSpeed', and 'optimizeQuality'; with the 'optimizeSpeed' value
> corresponding to keeping the image blocky (using "nearest neighbor" for
> the algorithm). This was a requirement from our users who need to be
> able to control whether or not a scaled image is kept blocky or
> smoothed. This works in Opera (Presto) but not in current Firefox or
> Chrome. (We also use this property to set/unset the PDF 'interpolate'
> entry in the image dictionary which effectively does the same thing, so
> at least export to print is correct.)

In Firefox the image-rendering value you need for nearest neighbour is
-moz-crisp-edges

Robert