Brushes

Done using GIMP 2.8 on Kubuntu Linux 18.04 LTS

We previously looked at the Paint tools available in GIMP, but to use any of them you also need to select a Brush to use with the tool. So it is time to take a look at Brushes.

All of the Paint tools, except the Ink tool, use the same set of brushes, though usually you use them with the Paintbrush tool. Try using brushes with a few different tools and you soon realize they don’t always work well with other tools. GIMP comes with a default set of brushes, but because it is open, you can add brushes as well. Brushes are technically pixmaps, short for pixel maps, and they are defined as:

A pixmap stores and displays a graphical image as a rectangular array of pixel color values.

https://franz.com/support/documentation/current/doc/cg/cg-pixmaps.htm

If you are only going to use the built-in brushes, or ones that other people have already created, the definition may not matter, but you do have the ability to create your own if you like. GIMP is written in the C programming language, and there is a standard C method for pixmaps, but this is not supposed to be that technical a tutorial so I would only suggest you do some Web searching as there are lots of references out there. (e.g. https://ergodic.ugr.es/cphys_pedro/unix/athena5.html)

The Brushes Dialog

The Brushes Dialog is found on the lower right and has all of the options for selecting brushes:

Brushes Dialog

At the top of the Brushes dialog are three tabs:

  • Brushes
  • Patterns
  • Gradients

So in general, you really have three dialogs in one. If you click the Patterns tab, you are in the Patterns Dialog, and so on. But they all work similarly. And for each tab, there are configuration options if you click the tiny button on the far right of the tabs which looks like a leftward-pointing arrow head. One of the things you can do which I would recommend is to View as List, instead of View as Grid. The Grid display is what you would get by default when you install the program, but when you View as List you get additional information that is helpful in getting to know your brushes:

GIMP Brushes View as List

This way you can see the name of the brush and the size of the pixmap. Remember that all brushes are just rectangular bitmapped images that you apply with your mouse or other pointing device.

Under the tabs, there is a dropdown that says “filter” very faintly until you have used it, but once you have used the filter function that goes away and you will either see the name of the filter employed or see a blank space. This lets you view brushes of a particular type, such as Basic, Legacy, Media, Sketch, and so on. You will also see any each of the brushes sets you may have added listed in here, so if you only want to see the brushes you just downloaded from DeviantArt (for instance), you can filter to show them. In the above image, for instance, MicroPatterns is the name of a collection of brushes I downloaded from DeviantArt and added to my collection.

Following this is the gallery of actual brushes for you to look at. If you double-click on one it opens the Editor, but note that the brushes that come with GIMP by default, and most likely the ones you download from sites like DeviantArt, are locked and not editable. But any that you create can be edited by you. Or for the ones that come with GIMP you can open them in the Editor, then make a Copy, and edit that copy if they are parametric. (See below).

Under that is the Spacing setting. This affects what happens when you click-and-drag the Paintbrush Tool with this particular brush. When you click-and-drag, you are setting down a series of images which will overlap. This setting determines how much space there will be between consecutive copies of the image. This setting is defined as a percentage of the brush width. If this is set to 100 there will be no overlap at all and you will have distinct images pasted, less than that and there will be some overlap and you will get some kind of continuous line.

At the very bottom is a row of icons: Edit this brush, Create a new brush, Duplicate this brush, Delete this brush, and Refresh Brushes. Selecting Edit, Create, or Duplicate will open the Brush Editor, but for ones that are locked you won’t be able to Edit unless you are working on a copy.

Adding Brushes

And for some good additions if you want to expand on the range of brushes available:

GIMP brushes come in three file formats:

  • GBR – This is the most common GIMP brush format, used for ordinary and color brushes.
  • GIH – This is for animated brushes with images from multiple layers.
  • VBR – This is a vector format, and like all vector images it can be resized without loss of clarity.

Brushes are simply files that you store in your brushes directory, and you can find just about anything at DeviantArt. It is free to join, and you can participate in the community there. If you download a brush from there, it will come in a *.zip file, which you can extract into your Brushes directory. You can make it easier to keep track of things by extracting into sub-folders, which is fine, GIMP will find them. Once extracted, you need to go into GIMP and “Refresh brushes”. With GIMP 2.8 that is done using the icon on the very bottom right that has the circular arrows:

Refresh Brushes is on the far right
Refresh Brushes is on the far right

The new brushes will then show up in your Brushes Dialog.

Creating New Brushes

There are several ways to create new brushes, either starting from scratch, or by making a copy of an existing brush and editing that copy, or copying all or part of an existing image. Brushes that are parametric can be edited by using the parameters in the Brush Editor. This means they are not raster-based, but vector-based, and can be resized without losing clarity, which is useful. Non-parametric brushes are those that are purely bitmaps and as such are a more advanced topic I won’t cover.

The easiest thing to do is start with an existing Brush and make a copy. So for example let’s start with a nice parametric brush, the Star:

GIMP Star Brush
GIMP Star Brush

To edit it, first double-click to open this in the Editor, then make a copy using the Copy this brush icon on the bottom. The Editor will now say “Star copy”. This can be edited by changing the parameters. First, the shape. Right now the Diamond shape is selected. Select the Circle and you get a rounded star:

GIMP Rounded Star Brush
GIMP Rounded Star Brush

And if you select the square it will look a little like a broken-down box:

GIMP Squared Star Brush
GIMP Squared Star Brush

Then there are the other parameters:

  • Radius – This changes the size of the brush.
  • Spikes – This determines the number of points on the star, or if you have a Square shape, the number of sides, so you get a polygon.
  • Hardness – Determines the amount of feathering on the border.
  • Aspect Ratio – The ratio of Width to Height. Increasing this will “flatten” the image.
  • Angle – This rotates the image.
  • Spacing – As we saw before, drawing a line with the paintbrush essentially “stamps” a sequence of images on the canvas. Set this to a low number and you get a solid line, increase it and you get distinct images.

Creating a new brush uses a similar process, except that GIMP chooses to start you with a small, fuzzy, round shape.

Finally, whenever you copy something to the clipboard in GIMP it also appears a brush until you put something else on the clipboard. These brushes normally do not last, but you can save the image as a brush by going to Edit–>Paste As–>New Brush. Of course, this is not parametric so you cannot edit it the way you do parametric brushes, but of course as a rasterized image you can edit it in GIMP before you save it.

Using Brushes

To use a brush, first select the Paint tool you want to use (usually the Paintbrush), then click on the brush you want to use in the Brushes Dialog. Then, you can click on a spot on the image, or click and drag. I recommend creating a new blank white image and trying a few to see what it is like and get a feel for it. If you click once, a single copy of the brush pixmap will be placed on the image. Bit if you click and drag, it is like placing a whole bunch of the pixmaps in a line. Bear in mind that the pixmap is itself just another image. This means you can be playful with brushes, such as Green Pepper or the Tulip, which you can place in any other image.

Also note that you can use brushes with the Eraser tool, and in that case you will erase something from the canvas instead of adding something.

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