The file extension PMG is used for so-called Photomerge Composition files of the image editing software Photoshop. Photomerge is a feature of Adobe Photoshop to combine multiple images into one panorama image.
Photomerge offers a variety of fine-tuning options when composing images, such as perspective correction, zoom, and overlap modes. These settings and the arrangement of the pictures can be saved in a composition file. Therefore, you need to a PMG file and the associated images.
The photomer function can be found under 'File -> Automate'.
Most often resolving problems with opening PMG files is very simple. Just install an appropriate program that supports such files. All of the listed programs support PMG files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of PMG files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate PMG files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the Adobe Photoshop applications is not on the list, select "Browse" option in order to manually locate the directory where Adobe Photoshop has been installed.
Sometimes problems with opening PMG files may not lie with the application itself, but can arise due to other causes, such as: