graphicxtras.com > Tutorial on Capturing patterns in Painter X3 12 using PNG files with original luminance etc
Above, the panel for the capture of patterns in Painter
Open the image or use an existing image. Go to the select menu and select all or use the selection tool / marquee in the Painter toolbox. Select the area you want to define as a pattern. You can find many pattern sets on the graphicxtras site and these can be used and they are all seamless, just selecting an area of an image will probably not make the tile seamless though it, of course, does depend on the image. Go to the patterns panel which can be found via the window menu and media control panels and then select the capture command. Once you have defined the item, you can use the captured pattern in features of the application such as clones and original luminance settings etc such as in brush strokes and also many of the effects in Painter
You can find the patterns panel in the 'media control panels' section of the window menu in Painter. If you can't see the panel then you need to go to that menu to display it. The right side menu comes with a range of commands such as rename the pattern as well as create an icon for it etc. The key one for capture is the capture pattern though. The define pattern and make fractal commands are of interest, in particular the fractal as you can use it to create some very unique tiles.
You can capture panel does have a few minor additional features such as name (as well as a very small preview which is pretty standard for Painter and still very surprising for 2016). You can generate a regular tile (and most of the time I go for that option) but you can also apply a horizontal shift or vertical shift to the tile and you can then use the bias to shift the alignment of the tiles. Useful for brick fills etc.
The great thing about the capture pattern is that you can select different areas of an image or perhaps apply effects and then capture the pattern. You can use the tool to create a snapshot of all kinds of images and type and effects to create a huge selection of tiles for use with brush strokes and clones etc
As mentioned, unless you start with an image that is seamless, you probably won't get a seamless tile but the pattern feature in Painter is great with either. You can also use the result of any generated tile as a new pattern (image) which can then be re-selected and used as yet another image to capture as a source for yet more tiles.
If you are interested in patterns then please check out the border patterns as well as rose petal patterns or perhaps if you want to create some Scottish themed designs then the tartan patterns may be of interest. There are many wonderful sets such as contours as well as Greek ornaments or you can use the brush strokes (which are often basically tiles as well) such as zigzags and grids 100 series or perhaps use the fonts as a great source for even more amazing tiles such as hexagon fonts
Capturing PNG images as a Painter patterns [Youtube] The video shows the steps to capturing a Painter pattern in version 12 as well as the application of a few effects / filters using the patterns