Screenshots are of low quality

My screenshots appear in both spectacle’s previewer and gwenview to be of poor quality, yet when uploaded here they are exactly how I expect them to be:

I’m using a 2560 x 1440 pixel display. Has anyone else experienced this? If so, were you able to remediate it? If so, how?

The answer is “Zoom to Actual Size” found in the “View” context menu. Do I feel like a numpty on Christmas.