thumbnail: Make thumbnailing multithreaded
Rework thumbnailing to support multiple concurrent threads. Also apply some optimisations.
Closes #1397 (closed) Supersedes !1128 (closed)
Edited by Khalid Abu Shawarib
Rework thumbnailing to support multiple concurrent threads. Also apply some optimisations.
Closes #1397 (closed) Supersedes !1128 (closed)