Correcting perspective from stitched panorama

[christinanorwood]

This is a stitched panorama (PTGui, 6 images). If this had been taken on film (e.g. 6x17) the facade would be rectangular. Is there any tool in GIMP that can 'rectangularize' such an image? The perspective tool doesn't really work because the falloff is curved.

[Ofnuts]

(Today, 12:01 AM)christinanorwood Wrote: This is a stitched panorama (PTGui, 6 images). If this had been taken on film (e.g. 6x17) the facade would be rectangular. Is there any tool in GIMP that can 'rectangularize' such an image? The perspective tool doesn't really work because the falloff is curved.

Film would have produced a distortion as well, because it comes from the technique: ff you are (relatively) close, the things at the center of the panorama are closer to the camera and therefore appear bigger. I have not used PTgui for ages, but it probably has a choice of "projections", some projection produce some kind of bend, while other don't.

Now, to fix the problem at hand, two ways, both in Filters > Distorts

Lens distortion:

   

Curve bend:

   

In both cases I eyeballed the result, you can probably get slightly better results

[christinanorwood]

(8 hours ago)Ofnuts Wrote:

(Today, 12:01 AM)christinanorwood Wrote: This is a stitched panorama (PTGui, 6 images). If this had been taken on film (e.g. 6x17) the facade would be rectangular. Is there any tool in GIMP that can 'rectangularize' such an image? The perspective tool doesn't really work because the falloff is curved.

Film would have produced a distortion as well, because it comes from the technique: ff you are (relatively) close, the things at the center of the panorama are closer to the camera and therefore appear bigger. I have not used PTgui for ages, but it probably has a choice of "projections", some projection produce some kind of bend, while other don't.

Now, to fix the problem at hand, two ways, both in Filters > Distorts

Lens distortion:



Curve bend:



In both cases I eyeballed the result, you can probably get slightly better results

Thanks very much, something to work with and looks promising. I think film would give a rectangular facade because although the height at the side appears less due to greater distance, it's projection onto a flat film plane would be larger (I think) because it's further from the lens (distance from lens to film plane). Certainly Nick Carver's panos taken with his Shen Hao 617 don't seem to suffer from the distortion shown in my image. Using a stitched pano the film plane is essentially a faceted cylinder by rotating the camera.

[denzjos]

Using PTGui, just load the panorama photo in PTGui, and set some horizontal and vertical control points on the building and create a new panorama from this previous made panorama. In the attached photo, I just used 3 horizontal points on the roof
   

[christinanorwood]

(6 hours ago)denzjos Wrote: Using PTGui, just load the panorama photo in PTGui, and set some horizontal and vertical control points on the building and create a new panorama from this previous made panorama. In the attached photo, I just used 3 horizontal points on the roof

That's an excellent result! Unfortunately my attempts to use horizontal control points don't produce nearly as good a result. Not sure what I'm doing wrong. Select a line that should be horizontal, place a point at one end in one image, and at the other end in the other image. Right? Repeat for a couple of other lines that should be horizontal. Optimize and create panorama.

[denzjos]

Change Lens settings /  Lens Type :  Cylindrical panorama