Thanks, I'll check this out in more detail tomorrow. Two quick thoughts:

1. It should probably also support Flip.BOTH
2. Would it deserve its own ImageServer implementation?

Currently we have RotatedImageServer, even though AffineTransformImageServer could also do the job. This avoids the need transform all x and y coordinates then build up the image pixel by pixel (or rely on Graphics2D rendering for RGB images). Here, you could instead extract rows and columns and simply reverse them.

To help answer, it would be worth checking performance with a large, multiplexed image, e.g., LuCa-7color_Scan1.qptiff or Patient_1.ome.tiff; you could benchmark tile reading using AffineTransformImageServer and RotatedImageServer to see if they are different enough to justify the latter.