Feature: Support ROI based rendering

[chafey]

Currently OpenJPH supports full image frame decoding. This works great for standard image sizes but does not work for very large size images (e.g. > 10,000 width x 10,000 height) as is found in Digital Pathology and satellite imaging. For these large images, the ability to extract a region of interest (ROI) is required to access the full resolution data without exhausting memory (and using unnecessary compute). This functionality is also a requirement to support JPIP. JPIP window rendering functionality would be a good source of requirements for the ROI rendering API (e.g. how to specify the ROI, resolution, quality)

Note this functionality would also require being able to support sparse cacheing/reading of HTJ2K bitstreams to minimize memory use. This could be done by reading from the file itself directly or over the network via JPIP or HTTP Byte streams

[aous72]

Hi Chris,

Thank you for putting this in.
I think it is useful to have this. I will try to do it in the next few weeks.

Cheers,
Aous.