02-03-2018, 07:36 AM
(02-03-2018, 06:06 AM)grit Wrote: When I scale down and rotate layers in 2.9.8/9, resolution is decreased and layer is blurred. I remember this wasn't like that before.
Is that a bug?
When you scale down, pixels are interpolated so you lose definition, even if this is not as visible as when scaling up. In some bad cases you can be hit by aliasing and get moirés and jagged edges, in which cas the solution is to pre-blur the picture before scaling down. In 2.8 the rule is to apply a gaussian blur of N pixels when you downscale by N.
Pixels are also interpolated when you rotate. This isn't very visible on the first rotation, but if you rotate things several times blur shows up around th the third rotation. If you want several copied of an object with varying angles, always produce them from the initial object and do not obtain copy N+1 from copy N.
Last, all geometric transforms (except the flips and the rotations of multiple of 90°) interpolate pixels, so the fewer you do, the better it is. Gimp 2.9 introduced a combined transform tool that has the big advantage that you can apply scaling, rotation and shear in one single operation (so you interpolate pixels only once and avoid the blurring caused by repeated interpolations.