Because so many panoramic tools have come and gone unmaintained over the years, I'm having trouble finding a good tool to view panoramas.

In short, I want something like IrfanView, but that also works with Hugin PTO panoramas. Here is a complete "wishlist":

  • Quickly browse through a folder containing a mix of both images and panoramas, in order of file name or date taken. (This seems like a rudimentary goal that everyone would do, such as browsing through the panoramas you took on your last vacation, yet I can't find any software to do it with.)
  • Pan, tilt, zoom the panoramas
  • Handle partial panoramas (less than 360 degrees)
  • Handle large panoramas
  • Must be free
  • Code should be somewhat maintained
  • File Format: Because I use Hugin for stitching, an app that directly reads the PTO file without having to output a stitched JPG/TIF would be a huge time and space saver. Otherwise, the viewer should be capable of reading either equirectangular and cylindrical projections, or both.

I've seen the list of viewers on PanoTools wiki, but it was last updated 2 years ago. There are many viewers listed, and many of them no longer exist.

  • 4
    \$\begingroup\$ This question is probably more appropriate at Software Recommendations. Here it is basically a request for a product recommendation, which are specifically off-topic. \$\endgroup\$
    – Michael C
    Commented Jul 2, 2018 at 22:23
  • \$\begingroup\$ I didn't know about that, thanks. I thought serious photographers are usually the ones using Hugin, so I thought here would reach the most relevant audience. I see "open ended purchase recommendations" in the off-topic list, but since I'm specifically asking for free software, I don't think that applies? I'm in doubt as to whether there is a single piece of software matching the criteria. \$\endgroup\$
    – mach
    Commented Jul 2, 2018 at 23:29
  • 2
    \$\begingroup\$ That's what the software rec group is all about. They usually post links for photography related inquiries to our chat room. \$\endgroup\$
    – Michael C
    Commented Jul 2, 2018 at 23:32

2 Answers 2


The pto files produced by Hugin are basically just configuration files. Some programs, such as Hugin itself, may be able to open the files and allow you to preview something that resembles what the final panorama may eventually look like, but because it is not the finished panorama, the preview will only roughly approximate the final output.

Generally, pto files must be processed into a real image format before they can be used with a viewer. Once in a standard image format, usually JPEG, they can be viewed with any image viewer. Special panorama viewers mainly just provide an immersive experience by further warping the image.

If you can create special metadata, Google Photos can be used as a viewer. Another web-based viewer is Pannellum, which may be used via a CDN to view panoramic images (replace %s with the URL of the image):


If you set up a web-based viewer on your local machine, it should continue to work for as long as you can use a browser that supports the technologies it is based on.

  • \$\begingroup\$ And as to the browsing part, most image browsers have facilities for things like showing images with a particular extension, and many also provide ways to open a particular file in another application... think modular. :) \$\endgroup\$ Commented Jul 3, 2018 at 3:45
  • \$\begingroup\$ An approximate preview may be sufficient for my purposes (browsing through a collection). I think it's a good trade-off considering the time and disk space required for stitching. My panoramas are very big and not trivial to render or store. I'm in doubt such an app exists though utilizing the PTO format. \$\endgroup\$
    – mach
    Commented Jul 4, 2018 at 18:43
  • \$\begingroup\$ Using a cloud solution or a web service that requires an already-uploaded panorama is just not feasible due to the size and amount of panoramas, keeping track of local and remote copies, and slow internet. So that removes pannellum CDN and Google Photos from potential solutions. Hosting my own web server to have a local copy of pannellum wouldn't be my first choice either, but possible. I'm not sure how to integrate that with a photo browser. I'm really only familiar with Irfanview and Lightroom. \$\endgroup\$
    – mach
    Commented Jul 4, 2018 at 19:00
  • \$\begingroup\$ you're using windows? how proficient are you at the command line? \$\endgroup\$
    – xiota
    Commented Jul 4, 2018 at 20:11

In Hugin, with the .pto project file open, go to the Fast Preview window (the button with the GL on it) select View → Overview in the menus to open the interactive Overview pane. This can be docked or floating using the little pushpin icon.

In Panosphere view, if you click and drag on one of the axes to rotate the sphere, you can check the spherical view from all angles to check for stitching errors. On MacBook Pro, I can zoom in and out by double-finger dragging left and right on the trackpad, but I have no idea what that would be with a mouse on Windows/Linux.

While it's looking at the sphere from the outside, rather than the inside, it can help you check for stitching errors without having to process the entire panorama first, and also quickly preview any corrections you perform via the Move/Drag tab.

See also: the Hugin documentation on the Fast Preview's Overview.


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