I have CS4. I do interiors, and they require layering lots of individual files together and making lots of selections, layer/layer masks, etc. Files get pretty unwieldy, 1.5~2GB. When all looks good, I do a Layer>>Flatten, then apply Edit>>Transform to get the image perspective perfected. However, if I want to go back and re-work an area, and I load one of my saved selections, it exists in its pre-transformed state. I don't care that individual layers are gone, I can usually get by with some subtle Hue/Sat or Level adjust. But not having the selections themselves get transformed along with the image is a bummer. Obviously, I am missing something when I do a Layer>>Flatten then Edit>>Transform.
You have a couple of choices. One is to straighten out your file before you start working on it. Second, and you have to do this while your original file is open - after you make your Free Transform to straighten out the image, you click on the Path you used to make your selection, activate the path, go to the Edit menu, down to Transform, then to "Transform Again". This will apply the previous transformation to your Path.
If you have saved your selections as additional Alpha Channels, then, after you do your original transform, you click on the Alpha channel to make it visible and then go to the Edit>Transform>Transform Again, which will apply the move to your entire channel. Again, this has to be done immediately after your tranform and before you close the file.
Ahhh- one by one for each alpha channel. I usually discard the paths once the selections are created. So I do this in the channels tab clicking on just each selection channel so just the white and black 'litho-like' selection image is visible?
I do understand the process of "transform again" by doing another one right away. To bad PS doesn't allow for some sort of save for that.
Paths are a much more efficient way of storing the selection information, unless you're doing something really complex to the selection like blurring it more on one side than the other. Paths add almost nothing to file size while alpha channels add a lot.
Yeah, as far as I know, you have to go through each channel one at a time. Probably why I do my transforming first whenever possible.