You're welcome. I looked into it because it would make a pretty cool project and while pretty advanced, not impossible.

The cheapest analog-digital-converter chip I found is the TVP7002. Dealing with the digital pixel output is still way way too much data, but now it might be possible to scan the picture a few pixels each loop. The reasonable approach would be to process it in an FPGA or specialized chip and only deal with a compressed and scaled image in the ESP8266.