Importing custom filters
Go to the Filters panel and you'll see the option to "import filter". Select that and you'll be presented with two options:
• "Scan filter" Use this to immediately scan a QR code for a custom filter.
• "Import from Photos" Use this to load an image from your camera roll that contains the QR code for a custom filter.
That's it! Once you've either scanned or imported from photos you'll now see the custom filter show up in your filters panel. It'll be under the "Custom" section if you ever need to find it again.
Note: Mobile users will see the option to scan filters, but users on the desktop will only be able to import from a photo.
(From https://support.polarr.co/wiki/product-features/Import-filters.html)
