PanoTwist – an editing tool for spherical panoramas
PanoTwist is a free and open source editor for fully spherical panoramas. PanoTwist can manipulate panoramas stored in the equirectangular format, which is the most common storage format. As the name suggests, these panoramas span a full sphere – that is, 360° x 180° in the horizontal and vertical directions respectively. They are sometimes referred to as Photo Spheres.
Here’s one example of such a panorama:
PanoTwist can perform the following editing functions:
- Patching nadir and zenith (using an image or a uniform color patch)
- Adjusting the initial view position
- Optional re-scaling (if there is a limit on size – for example, for Facebook uploads)
PanoTwist is open source and is licensed under the GNU General Public License. The source code is available at https://github.com/dizzylogicc/PanoTwist. You are welcome to download and install the 64-bit Windows version below:
PanoTwist was designed with a fairly straightforward, simple to use one-page interface:
To use PanoTwist, a folder containing one or more equirectangular panoramas needs to be opened. This is accomplished by clicking the Open Folder button and selecting one of the panorama files in the required directory. The software then analyzes all JPEG and TIFF files from that directory and selects ones that have the correct aspect ratio (2:1) for equirectangular panoramas.
These files can then be edited one by one or as a batch. You can switch between the different opened panoramas by clicking the Next File and Previous File buttons.
Adjusting the initial viewpoint
The initial azimuthal viewpoint for the current panorama can be adjusted by dragging the main panorama image left or right. The cross-hairs at the center of the image indicate the initial viewpoint that will be shown when the image is viewed by a panorama viewer, or uploaded to Facebook or another panorama-aware web service.
Patching nadir and zenith
Fixing nadir (directly below the camera) and zenith (directly above) is a common task after fully spherical panoramas are stitched together. Usually after stitching the nadir looks similar to the image below, with the unphotographed area visible in black and the legs of the tripod showing around it:
To patch the area around nadir or zenith using PanoTwist, click the appropriate checkbox to the right of the main image area. The angular size of the patch can be adjusted using the patch size spin box. Three options to patch nadir/zenith are available:
- Patching with the average color. The patch is automatically set to the average color of non-black pixels underneath the current area of the patch.
- Patching with a specific color. To patch with a specific color, select the corresponding radio button and paste the required color in the hexadecimal notation (e.g., #1AB345) into the color edit box.
- Patching with an image. Select the image which will be placed over nadir or zenith. The central circular area of the image will be used.
As an example, here’s the same nadir patched with a user-supplied image that displays contact information for a fictional photography company:
If there is a hard limit on the dimensions of the panorama, you can specify the maximum size, and the software will automatically downscale the image if it happens to be too large. Facebook, for instance, only allows panoramas 6000 x 3000 px or smaller to be uploaded.
Saving individual images
After the changes are made, the image can be saved by pressing the Apply to Current Image and Save button. PanoTwist edits images non-destructively; that is, the initial image will not be modified. Instead, the panoramas will be saved in the subfolder named /Panotwist output/ that will be created in the selected folder. The image names will be preserved in the subfolder.
Saving images in batch mode
It is also possible to apply the changes to all opened panorama images by pressing the Apply to All Images and Save button. In that case, the same nadir, zenith and rescaling options will be applied and the resulting files will be saved in the /Panotwist output/ subfolder. The initial view position will not be modified; to change the initial viewpoint, images need to be processed and saved individually.
Planned future improvements
In the future I am planning to add some additional features; among the first should probably be the options to set the vertical (polar) view position and field of view in both directions. Feel free to drop me a message if you think of some other useful features or find a bug.
- PanoTwist requires 64-bit Windows Vista or later to run.