Hey @Nurlan_A ,
Coda is using an image compression and storage engine for images placed on the canvas or in image columns. This is most likely to make sure latency is low and user experience is high.
Paul made a little guide on how to get better image quality here, but that requires some work – and usually the quality should be more than sufficient for most purposes. At least this should give you a chance to restore a better quality or compare the compression.
Also I personally don’t think it has something to do with subscriptions, but not sure.
Best
Daniel