[whatwg] Supporting scanners on the web

[Benjamin Smedberg]

One of the use cases that has come up for why people are still using 
plugins is supporting scanning to the web, in particular multi-page 
scanning. It seems to me that we could hook this up to <input 
type="file" multiple>, but that we should try to provide UAs with a hint 
that a page expects a document instead of images. This primarily may 
affect whether/how the browser presents a scanner option to the user in 
addition to or instead of camera/photos when selecting an image.

A couple questions I've thought about but don't have answers to:

* Do/can PNG images contain information about their resolution, so that 
the site can reconstruct the actual page size?
* Should we give the site any way to specify preferred resolution or 
color depth for an image? Or should the site be prepared process any 
images to the required resolution, convert to monochrome, etc.
* Should the spec recommend any specific MIME types for scanner page 
images? Most desktop scanners appear to default to .tiff, but that's not 
a normal web format: perhaps we should recommend that UAs convert to PNG.

--BDS