Make a smart object out of the layer(s) that you need to rotate by selecting the layer(s) in the Layer panel and chose Convert to Smart Object from the Layer panel flyout menu
Margaret,
If you’re on CS4 use the rotate tool. This doesn’t do anything to the pixels in the document, it rotates on screen only.
Rob
As the previous poster said – use non-destructive transform methods wherever you can. Apart from that, note, that rotating in multiples of 90 degrees does not change the pixels’ color and transparency information, as this always coincides with the imaginary rectangular/ square pixel grid and pixels only get re-arranged. Only rotations at different angles will enforce resampling, meaning that in particular edges will be recalculated to keep them visually smooth. Doing this multiple times will result in softening, as the way Photoshop works, it has no knowledge of previous transforms and will apply the full sampling again in a "dumb" manner. Smart objects avoid that limitation, as they concatenate operations, i.e. a rotation of +60 degrees followed by one -20 degrees will be treated as a single 40 degree rotation. Likewise, CS4’s canvas rotation, is merely a secondary rotation applied to the screen buffer, not affecting the image itself.
Mylenium
Thank you for the helpful information. I don’t seem to have Smart objects(PS7). Because I have to rotate the whole image (all layers at once) I have to use menu Image/Rotate Canvas. If this is non-destructive as the stated above then it wouldn’t seem to be a problem to rotate multiple times. What I might do is work with 2 files instead of one, one for the top and one for the bottom, then when it’s done, place one image into the other and just rotate it once with the rotate tool.
As stated above, it’s non-destructive only if you rotate in 90 degree increments otherwise you will lose image quality
If the rotation uses always the same source
image, then it can be executed hundred times
without accumulating errors. Why the heck has
the New rotation to be based on the Last image ?
No, image processing isn’t ‘destructive’ if one
doesn’t overwrite the source.
Best regards –Gernot Hoffmann
