graphicxtras.com > Tutorial on Capturing paper grains in Corel Painter using PNG files (version 12) for textures / overlays etc
Above, panel to capture textures / grains / paper from images in Corel Painter (back in the past, the papers were mainly listed as grains, I still often just call them that)
Early versions of Painter could not load PNG images so to capture the PNG image as a paper / grain file requires an initial step,such as converting the PNG image into JPG etc. The reason I mention PNG images being that most of the pattern sets and brush sets on this site include the textures in PNG. You can find many free apps on the web that can convert PNG / JPGs etc such as Irfanview
OK, once you have the PNG images and opened them. Go to select menu and set ALL. Go to the papers panel (found via the paper panels in the window menu) and right side menu and capture paper. All the PNG images for patterns are seamless, the paper grain will also be seamless. The paper grain has now been captured and can be used as a paper file in Painter. You can now set the scaling and constrast and brightness as well as capture additional presets in the application
If you wish to permanently save the paper file then you have to save the captured paper grain to a paper library. Go to the paper libraries panel and right side menu and export paper library (select the correct paper library - probably paper textures) and export the captured designs. You can then re-use the Painter paper library at any time in the future (as long as the format is still valid).
Capturing PNG images as a Painter grain Youtube video
The video shows the steps to capturing a Painter paper in version 12 as well as the application of a few effects / filters using the papers