Issue with some Aperio SVS files

[Benjamin Gilbert]

On 06/04/2014 10:28 AM, Derek Magee wrote:
> A lot better thanks, however one remaining issue is that the bottom of
> the image appears to have missing tiles at low zoom which are output as
> transparent (see below – I made transparent pixels red to check it
> wasn’t just outputting black).

Right, those are the missing tiles.  It seems they are always on the 
right or bottom edge, and only in levels other than 0.  ImageScope is 
probably working around them by downsampling tiles from level 0.

In general, OpenSlide tries to return slide data with a minimum of 
processing.  For example, we don't usually synthesize pyramid levels, 
even when the levels in the slide file are far apart.  That's why we're 
returning transparent here.  But in this case, it's clear what the slide 
file *meant* to say, and it's easier for us to fix the inconsistency 
than the application.  So perhaps we should revisit this.

Derek, could you give a rough idea of how many slides you have with this 
problem?  Do you have slides where the transparent areas impinge on 
meaningful content, as opposed to the background color?  Can you send me 
a couple samples for testing?

Thanks,
--Benjamin Gilbert