How can I turn a distorted spherical/equirectangular image into a normal rectangular photo?

Asked 6/10/2015

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I have a single image that appears to be part of a 360° spherical/equirectangular panorama, and I want to convert it into a normal rectangular-looking photo. Is there a way to remap this kind of distorted image into a rectilinear image, even if I only have this one remapped frame rather than the original fisheye source?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

11y ago

2 Answers

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The problem is that you're already starting with a remapped image. You're clearly working with a single member fisheye image that's been remapped as part of an equirectangular 360x180 panorama. It would be a lot easier if you just started out with the original fisheye image, rather than this remapped version. (See: What software should I use for converting fisheye photos to normal rectilinear photos?)

I took it, added whitespace around it to fake it being a member image in an equirectangular 2x1 image, brought it into Hugin as an equirectangular image (select "equirectangular" as the lens type, and 360 for the HFOV), and then remapped it to rectilinear (you can select a number of different projections on the Projection tab). You'll have to zoom in and crop pretty tightly, since the main remap will look like a big X. You might actually find Architectural or Panini more pleasing and closer to what you're looking for.

enter image description here

Originally by user27440. Source · Licensed CC BY-SA 4.0

user27440

11y ago

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AI Answer

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Yes, but results are limited because your starting file is already a remapped image. If this image came from a fisheye shot that was converted into an equirectangular 360x180 panorama, the best approach is to start from the original fisheye image instead of the already-remapped version.

If you only have the spherical/equirectangular image, you can still try reprojecting it in panorama software such as Hugin:

  • load the image as an equirectangular source
  • set the lens/projection type to equirectangular
  • use a 360° horizontal field of view if appropriate
  • remap/export it using a rectilinear projection

In Hugin, this is done by importing the image as equirectangular, then choosing a different output projection on the Projection tab.

Expect to zoom in and crop fairly tightly. A rectilinear view can only cover a limited angle before stretching becomes extreme, so you usually extract a smaller “window” from the spherical image rather than converting the whole thing cleanly into a normal photo.

UniqueBot

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11y ago

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