Dzi Viewer using CPP
I made a tiny example program that displays a libvips image in a window:
It's about 300 lines for the entire thing. It uses gtk+3, but it should be simple to adapt for other toolkits.
The cool thing is that it doesn't just display an image, it displays the end of a libvips pipeline, and it does it asynchronously. You can scroll around the image and the display will be updated in the background by a threadpool as chunks of the image are computed.
For your application, you could use
vips_arrayjoin()to join up the tiles of the DZI image, then display the output of arrayjoin in the window.
There's a more complete image viewer here:
Though I still haven't got around to finishing it, unfortunately.