Re: [Gimp-user] Rotate?

["Erik P. Olsen" <epodata gmail com>]

On 05/02/12 13:37, Noel Stoutenburg wrote:
> Erik P. Olsen wrote:
>
> > Why can't I rotate images similarly with Gimp?
>
> and I concur with the answer that BK gave, as far as it went. But to expand a
> bit, there are several ways to rotate an image. For the purpose Erik mentioned,
> I'd use the method BK mentioned:
>
> Image > Transform > Rotate...
>
> This is the equivalent of rotating the substrate upon which the image lies.
>
> There is a second way, useful when one wants to modify some part (or all) of the
> image with respect to the substrate.
>
> Layer > Transform > Rotate...
>
> acts similarly to the method BK described, except that it rotates the layer
> containing the image, or some part of it, with respect to the rest. If one has
> an image that has unequal dimensions, like a rectangle or oval, and rotates the
> layer relative to the substrate (canvas is the term GIMP uses), then part of the
> layer is no longer over the substrate. This gives a result similar to what the
> OP describes: part of the image is no longer over substrate, and gets lost.
>
> A third method works similarly to the method of the layer transform: the Rotate
> tool in the toolbox. The rotate tool will rotate a selection of the image (which
> may, but need not necessarily coincide with an image) and rotate that selection
> relative to the remainder of the image. And just like the layer transform I
> describe above, there is a risk that a selection with unequal dimensions will
> lose part of the information.
>
> It turns out, though, that even if one seems to have lost the information by
> choosing layer or selection rotation instead of image rotation, that besides
> undo, there is a convenient way to recover the information no longer over
> substrate. One can resize the canvas. Once the canvas is resized with the
> dimensions of the image again matching the dimensions of the rotated part, the
> full image again becomes visible.

Thanks for this detailed description. Yes, I've rotated the layer only, so now 
at least I know how to rotate correctly. But please enlighten me why would you 
want to rotate a layer and not the entire image?

--
Erik