How to use the transform tool for a proportional stretch?

[symphy]

Hey all!

I'm trying to find a way, if any, to do what I call a "logarithmic" transform, for lack of a better term. You know how some high-end HDTVs stretch the sides of an image proportionally, so the center remains unstretched, and the sides gets stretched more and more as you get towards the edge? That's what I find myself wanting to do almost daily in Photoshop, and not finding a good way.

An extreme example for conversation purposes:



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While that technique (grabbing a bar and transforming it to fill the necessary space) works great on skies and sand and uniform backgrounds, the line is much more obvious on complex backgrounds (like the above). Now, what I usually do to get around this is copy the little bar I'm going to stretch onto a separate layer, transform it there, and then gradient-mask it to blend into the bottom, as such:



This gets rid of the line, but has disadvantages, such as repeated leaves, etc.

I want to do a transform stretch that functions like the HDTV algorithm. Any suggestions? Am I explaining it right?

[thehen]

I've just tried a million different ways to do this and I can't figure it out.

It's like stretching a selection but the closer the pixels are to the edge you're pulling, the more they stretch. There should really be a function under transform which does this.

Sorry, I don't know what to suggest.

[symphy]

It's like stretching a selection, but the closer the pixels are to the edge you're pulling, the more they stretch.

That's probably a little clearer a description than the word "logarithmic". Thanks. That's what I'm getting at.

It would be really really really useful, especially when, for example, you have a 4x6 that you need to recrop to an 8x10. Suppose I have the following 4x6 image:



If I were to send this image to the printer and ask for an 8x10, I'd get this back (due to 8x10 being a squarer aspect ratio than 4x6):



Obviously, that's unacceptable. But so is asking the printer to print it 8x10 without losing data, because then you get "letterboxing" on the side:



So clearly, the best way around this is to add more background to fill the gaps. But again, without a proportionally stretched HDTV-style way of handling this, you get:



Now, obviously, with some clever tweaking and blending and clone tooling, you can actually acheive something far better than the above. But my point is that there should / must be a way to just do a logarithmic stretch in the first place, so that all that additional work isn't necessary.