Updated : 2021
How to create new brushes from Photoshop patterns tutorial. This tutorial is based on the PNG files on this site, similarly works for other PNG etc files (it can also be used with patterns from PAT files as well). You can just open the PNG file and define that. You can also apply different effects to the artwork as well as duplicate the pattern layers and then define that as a brush stroke. You can also obtain the patterns from PAT files and define those also as new brushes in Photoshop. You can also use the result of a pattern fill layer content to create a new brush in Photoshop. You can add masks to the pattern layers and use that as a source for new brushes. You can also use patterns with scripts to create all kinds of unique brush stroke designs. This tutorial shows you a number of methods to create brush strokes from Photoshop patterns
Apply pattern design (fill layer, styles, edit menu fill etc)
Edit menu in Photoshop
Define brush
Brush name
OK
Apply brush stroke via brush tool etc
Open the PNG file or use the place command in Photoshop - that is the first thing, once loaded it can then be manipulated in a number of ways such as adding effects or using it on channels etc - as with most things in PS, there are 100s of ways of creating new and exciting brushes.
Open PNG file and go to the edit menu define brush. You can define the entire file or just use the rectangular marquee and then select part of the artwork and define that as a new brush.
Once you have a brush defined, you can also go to a new document and then apply that multiple times, perhaps mixed with effects etc, and define that as a new stroke as well. That is a fairly basic way of creating infinite numbers of new brushes based on patterns designs however you can go even further by using the patterns with features such as fill content and that can also be defined as a new brush stroke
Open PNG pattern file
Edit menu in Photoshop
Define brush
Give it a brush name
OK
Select a brush tool
Select brush
You can also open the PNG file and then duplicate the layer of the pattern and re-size that and flatten and then define that as new brush stroke or perhaps add effects to the artwork before the definition
If you don't have the PNG files, you just have the PAT file. You can quickly create the PNG file or a source for a brush simply by using
Edit menu
Fill
Select patterns
Select a pattern and hover over the thumbnail to see the size (say 1000 x 1000)
Cancel out of fill
Create a document with the same size via file menu and new
Edit menu
Fill
Pattern
OK, You now have the equivalent of the PNG file and you can now just use
edit menu
define brush
brush name
OK
To define the brush stroke
You can also open the PNG file and then define it as a pattern via the edit menu. Once it has been defined, you can now use the pattern via the edit menu fill command and select pattern (and perhaps use it with the random fill or symmetry options to create even more interesting designs. If you create a layer then you can also add content to that and then use the layer menu and layer styles and pattern overlay (and you can also use the patterns as wonderful brush textures which can be permanently incorporated into the art) and that can also be quickly used as a great source for new brush strokes by flattening the artwork and then selecting part of the design or all of the pattern fill and then use the edit menu define brush command.
For myself, the best approach is probably the fill content which can be made of a solid color or gradient or pattern. The pattern can be scaled using the fill content layer scaling and re-colored using adjustment layers etc and the result of that layer can also be flattened and then selected or part selected and then edit menu and define brush to save the pattern as a brush.
Edit menu in Photoshop
Define pattern
Layer menu in Photoshop
New fill layer
Pattern
Select the pattern
Scale as required
OK
edit menu
define brush
The pleasure of the fill content is that is a layer and multiple layers can be generated and blended using blending modes such as darken and lighten etc to create all kinds of unusual designs which can be then flattened and again, selected and defined by the edit menu and define brush command.
Another good thing about a fill content layer (once it has been rasterized or turned into a smart object as the fill content layer can't have a layer mask in its default state) is that you can always add a layer mask to it via the layer menu and layer mask and then in the layer panel, you can modify the mask so the edges of the image are faded so you won't end up seams in the brush stroke (if that is not an issue then you should not worry about it).
You can also create unique pattern designs for use as a brush stroke by using scripts. If you use scripts, you probably be best to start with a selection for the pattern to fill.
Elliptical marque tool
Create a circle selection
Select menu in Photoshop
Modify
Feather
10px
Edit menu in Photoshop
Fill
Contents: Pattern
Select custom pattern
Script ON
Random fill
OK
Set density
Scale factor
Rotate pattern ON
OK
Perhaps re-apply the fill a few times to fill the brush stroke
Select menu
Deselect
Edit menu in Photoshop
Define brush
You can use the scripts to create all kinds of super unique brush strokes from the patterns. Random fill is particularly good but all the other scripts can be used