I've been using GIMP on and off for a few months now, and have got to know it pretty well for my purposes. Since GIMP is quite functional for skinning and profile painting, and is an easy choice for those who either prefer freeware, are linux users, or are wanting to test the waters without laying out the cash for PaintShop or Photoshop, I'm putting together a few tutorials that I hope will help out.
In this article we'll be looking at brush and color management, with the brush tools being a particularly difficult spot for some just starting out with GIMP. What we'll aim to do here is cover the ways to add and manage brush libraries, as well as talk some about brush edits.
Note that the screenshots in this article were taken on linux, and may look slightly different than a Windows machine.
Firstly, we'll add some new brushes. To start with, I've created a small library of round brushes with different sizes and hardnesses. These brushes are very similar to those I've frequently used in Photoshop. You can download this set of brushes from the Simmers Paint Shop download library here:
http://www.simmerspaintshop.com/foru...do=file&id=135
After downloading and unzipping the folder containing the brushes, now we'll add them to GIMP. The first point to consider is how GIMP manages brushes. From the main GIMP window (the one containing the tool buttons) choose FILE>PREFERENCES to open the main GIMP preferences window. Now click to expand the 'Folders' menu item, and you'll see the 'Brushes' item inside. Here's a screenshot of what you'll see:
Lets describe what these options control. Firstly you'll see that there are a few entries listed already in the brush folders section. These are the default brush locations. Any with check mark boxes beside them can be written to if you make a brush edit. Uncheck the box beside any directory you wish to protect from changes.
It's important to note that you can have multiple folders containing brushes which GIMP will load on startup. This gives nice flexibility when choosing which brushes will appear in our brush palette window. Now lets use this knowledge to install our new brushes. Navigate to a location where you'd like to have these new brushes permanently stored. I've chosen to place them in the same folder which holds the default GIMP brush set, but it can be where ever you wish. In this screenshot you can see the original brush folder inside the GIMP 2.2 directory, and just outside on my desktop I've got my own new brushes saved in the 'adlabs6 brushes' folder. I'll just drag my new folder into the GIMP 2.2 directory and I'm done.
Now back in GIMP, you can head back to the brush folder control panel and add the new directory by clicking the 'new' icon above the folder list. From here I pointed to the correct directory and clicked OK. Be sure to realize that all the directories listed on the brush folders page will appear in your brush library in GIMP, so any folders containing brushes you DON'T want included, be sure to delete them from this list (you can add them again later if you wish).
And so now I've got everything set. Restart GIMP if needed, and take a look at your brush palette and see if it's what you've got. Here's mine:
Now I'll talk some about how the brushes are arranged in the palette. As far as I can tell, any of the brushes in the GIMP brush palette are arranged alphabetically, without regard to which brush folder they are drawn from. This will cause havok if like me, you enjoy having your brushes all arranged in very organized groups by type! After some tinkering with the naming idea, I found that I could actually control the way the brushes appeared by renaming the brushes according to how I wanted them grouped in the palette. you can see the results of that in how nice my palette looks in the screenshot.
If you add some other brushes later on, you can keep this in mind when building your library. It takes some extra time but is worth it when the workflow is so much smoother while working.
Brush Editing Essentials
In the second part of this article, I'll talk briefly about the GIMP brush editor. To open the brush editor dialog window, simply double click on a brush in your palette which you wish to edit but keep the following in mind:
Note that if you have not enabled your brush folder to be writable when installing it (covered above) then the controls on this dialog will not be functional!
Note that any edits to a brush are saved to that brush immediately!
So... if you don't want to permanently edit a particular brush, be sure to work on a duplicate (right click and duplicate) instead of an original. Also remember that the newly duplicated brush will appear in the palette according to it's naming, so you can edit that while editing other brush parameters to put the brush where you want in the palette.
Now that we've covered those important points lets move on to what the slider controls on the brush editor do.
First up is the shape control buttons, and as expected clicking these will change the shape of the brush. Very straight forward.
The 'Radius' slider controls the overall diameter of the brush. This number appears to be the radius of the brush, not the diameter.
Next the 'Spikes' slider. This most obviously works with the square and diamond brush types. For the square it controls how many sides the square will have (above 4 and you'll get non-square shapes such as hexagons), and for the diamond brush it controls how many points the diamond will have (again above 4 will create stars having more points). The spikes control also works with the circle shape when used in conjunction with the 'Aspect Ratio' slider, covered below.
The 'Hardness' slider is quite important for most of the work you'll cover in skinning or profiling. It controls how sharp, or well defined, the edge of the brush will be. A value of 1.00 is fully sharp, while values approaching 0.00 will be increasingly softer.
Quite a bit of variation is possible with the 'Aspect Ratio' slider depending on the brush shape. I'll break this down based on each type:
Circle – If you vary the 'Spikes' slider to 3 or above, then the 'Aspect Ratio' slider will deform the circle into rounded forms. You can create many shapes with these sliders:
Square – Adjusting the 'Aspect Ratio' slider will vary the depth of the sides between the outside edges of the shape. For a 2 'spike' setting you'll just see the square deformed vertically into a dash. But for 3 or more 'spikes' you'll see the arms of the shape grow more or less deep:
Diamond – Similar to the square shape, adjusting the 'Aspect Ratio' for a diamond will vary the depth of the spikes around the shape.
The 'Angle' slider will as expected rotate the angle of the brush through 180 degrees. Very useful for adjusting a star shaped brush, where you'd like to have a spike point to a certain direction.
Finally, the 'Spacing' slider controls how frequently the brush shape is sampled as it is dragged over the artwork. Higher numbers will leave a larger space between the samples, smaller number will draw a nearly continuous line, though very low values can slow down some computers as the processor works to keep up with the drawn line while sampling the brush over the path.
I'll add a finer explaination on what the slider value actually means now, for those wishing to control the tool in a more precise manner. The number is the percentage of the brushes width that is skipped before a new mark is made. So a circle brush of 100 pixels diameter, and a spacing of 5, will have a new mark placed with 5 pixels steps across the artwork. That same brush with a spacing value of 50 will place the round brush marks so that the next mark's edge will be centered on the center point of the previous mark. Of course a 100 setting will have each mark's outer edge touching with no overlap, and going over 100 will leave a blank space between the marks. I've used this to quickly create rivets, using a value of 250 or so for a 1pixel brush, then clicking along the desired path. Automatic riveting!
Below is an example image showing spacings of 5, 50, and 100.
Conclusion
I hope this has been a useful introduction to the brush system in GIMP. It's a powerful and flexible system that can handle most of the tasks that a skinner or profile artist will throw at it. There are some user friendliness issues in my opinion, but for a avid user these can be worked around with only minor annoyance. Happy painting!