Fake a photosphere with ExifTool
I like to incorrectly use photo features to see what interesting stuff happens. In this case, I want to upload any random image to Flickr and make it display as a photosphere.
Photosphere’s are just regular flat JPG images, but the recorded image is a projection (probably “equirectangular”)–just like a map is a flat representation of a globe. Photosphere viewers know how to display the image to correctly unwarp the projection to make it appear like a 360 degree view. The viewer relies on some embedded metadata to tell it that the JPG could be viewed in this way. If you upload a valid photosphere to Flickr, the photo page will trigger a special in browser viewer so you can check out the 360 view.
The upshot: if we add the correct metadata to an image, we can trick Flickr or other viewers into displaying the image in 360, with odd and fascinating results.
As far as I can tell, Flickr requires four XMP tags in the GPano namespace (it is similar on other platforms), which in xml would look like:
<GPano:FullPanoHeightPixels>5000</GPano:FullPanoHeightPixels>
<GPano:FullPanoWidthPixels>10000</GPano:FullPanoWidthPixels>
<GPano:ProjectionType>equirectangular</GPano:ProjectionType>
<GPano:UsePanoramaViewer>True</GPano:UsePanoramaViewer>
ExifTool
To manipulate image metadata you need ExifTool. Truthfully, nothing else works reliably.
On Linux install ExifTool as the Perl library, e.g.
sudo apt install libimage-exiftool-perl. On Windows download the standalone package.
To use ExifTool, we start with the command exiftool and the file name of an image.
For example, the command exiftool test.jpg will print out all the current metadata embedded in test.jpg.
From there we add flags to the command to add or change the image’s metadata.
For example, the command exiftool -all= test.jpg will delete all embedded metadata, i.e. replacing all values with nothing.
To figure out how to add the photosphere tags dig through the XMP Tags docs to find the correct keys.
For example, to build up the command flag we want to add XMP metadata (-XMP), from GPano namespace (-GPano), in the tag ProjectionType (:ProjectionType), with the value of “equirectangular” (="equirectangular").
Thus to add/change that one metadata value, the full command would be:
exiftool -XMP-GPano:ProjectionType="equirectangular" test.jpg.
We can add multiple tags simply by adding more flags.
Fake a Photosphere
Here are the steps:
- edit image to 2:1 ratio (for reference, Pixel 2 camera shoots real photospheres around 9000px width by 4500px height).
- remove all existing image metdata:
exiftool -all= test.jpg - add the new fake photosphere metadata (be sure to replace the pixel dimensions with the actual size of your image):
exiftool -XMP-GPano:FullPanoHeightPixels="4500" -XMP-GPano:FullPanoWidthPixels="9000" -XMP-GPano:ProjectionType="equirectangular" -XMP-GPano:UsePanoramaViewer="True" test.jpg - upload to Flickr or other viewer
Some Other Viewer
Checkout my project sphere-view that uses Pannellum photosphere viewer, in a minimal Jekyll template on GitHub Pages. You don’t actually have to fake the metadata if you use this viewer…