Open up the image you would like to use by going to File>Open. I am using the image below:
Grab your zoom tool and zoom into the face. Now, grab your healing tool. You can make your brush larger (if you desire) by going to scale. Then find a clear patch on the face then click Ctrl on your keyboard and left click on your mouse. Now start clicking over any pimples and red spots on the face. Here is how my image looks after:
Now, grab your smudge tool and set the rate at anywhere from 16-20. You are also going to want to select a fuzzy brush and set the brush size to your liking then smudge all over the face and any other skin area that is showing. You're Done! Here is my outcome:
Need more help? Check out the video below:
Figure 14.85. The Airbrush tool in Toolbox
The Airbrush tool emulates a traditional airbrush. This tool is suitable for painting soft areas of color.
3.10.1. Activating the Tool
You can activate the Airbrush tool in several ways :
From the image-menu, through : → →
By clicking on the tool icon: in the Toolbox,
By using the A keyboard shortcut.
3.10.2. Key modifiers (Defaults)
Ctrl changes the airbrush to a Color Picker.
Shift places the airbrush into straight line mode. Holding Shift while clicking the mouse Left Button will generate a straight line. Consecutive clicks will continue drawing straight lines that originate from the end of the last line.
Figure 14.86. Airbrush options
Normally, tool options are displayed in a window attached under the Toolbox as soon as you activate a tool. If they are not, you can access them from the image menu bar through → → which opens the option window of the selected tool.
- Mode; Opacity; Brush; Size; Aspect Ratio; Angle; Spacing; Hardness; Dynamics; Dynamics Options; Force; Apply Jitter; Smooth Stroke; Lock brush size to view
See the Common Paint Tool Options for a description of tool options that apply to many or all paint tools.
Motion only: if this option is checked, the airbrush paints only when it moves.
The Rate slider adjusts the speed of color application that the airbrush paints. A higher setting will produce darker brush strokes in a shorter amount of time.
This slider controls the amount of color that the airbrush paints. A higher setting here will result in darker strokes.
GIMP for artistic work (and beginning level airbrushing)
Setting up GIMP for Artistic work
This tutorial will tell you how to configure GIMP to be more intuitive for artistic work and finishes with you creating a nice little artistic painting. It has been rewritten extensively to also take advantage of the new features of GIMP2.4.x and higher. This tutorial don't assume much previous knowledge of GIMP, but it's not for those using the program for the very first time. You at least need to know where things are. If you are new, you should start with the [Beginning GIMP] tutorial so you have the basics. That tutorial will also tell you how to adjust GIMP's interface to best suit you. You want to be able to focus as little as possible on GIMP, and as much as possible on your art after all.
This tutorial is divided into several parts, as follows:
1) Setting up keyboard shortcuts in GIMP for easing artistic use This little section gives you some hints on setting up your work environment to ease artistic use.
2a) Setting up the artistic tools -- some useful brushes. This section helps you create some basic but extremely useful default brushes you'll often want to fall back on. It also explains what advantages these brushes offer over brushes you modify with the brush scaling feature of GIMP2.4. These are what we will use in part 4.
2b) Setting up keyboard shortcuts for brushes Here we configure GIMP to allow you to modify the size and other features of your brushes with a keystroke.
3) Setting up the artistic tools -- about the tools themselves. This section details the various paint tools of GIMP and gives some advice on what tool settings you could start out with. Obviously it is up to your personal style and experience what you will prefer to use for your own work.
4) Starting out with artistic use of GIMP. In this last section we make practical use of our new setup by learning how to paint with the powerful airbrush tool. This section is very useful for anyone starting out doing art on the computer, especially if you are using a mouse. By doing a series of small exercises you should gradually get used to the tools and finally you end up doing a simple and fun drawing project to create a dead tree. Many have tried this over the years and had a lot of fun with it, so don't be shy to post your result!
This tutorial is especially suitable for you who is drawing with a mouse, and doing the exercises herein will hopefully help you getting better at drawing free-hand with the mouse (there are hints for tablet artists as well though). This is unfortunately not something you can just learn a "trick" for, you have to train it like any form of art. I have worked with the mouse in this tutorial to show that you don't require a drawing tablet to achieve nice hand-drawn effects. I use GIMP under Linux Debian but the windows choices etc should work the same under Windows and Mac. The images where taken using GIMP2.2.13, but even though things might look a little different in later versions of GIMP, the methodology is the same and you should still be able to find your way without any trouble.
1) Setting up keyboard shortcuts in GIMP for easing artistic use
A critical thing in GIMP art making is learning to use the keyboard shortcuts. GIMP is very powerful in this regard -- it's easy to assign any keyboard combination to any common function you use.
Make sure you have Preferences->User Interface->Use dynamic shortcuts selected, then you can just highlight any menu option and press the key you want to use for it. Don't be afraid that you're overwriting some default shortcuts -- a guideline is that if you don't know that shortcut now you won't be missing it later either (and if you do you can just assign a new shortcut). You can find a list of all GIMP's default shortcuts in this |list| on gimpusers.com.
The idea when setting up keyboard shortcuts is that you don't want to have to move your "painting hand" away from the drawing more than absolutely necessary. Most default ones are ok already, but if you change anyone, go for shortcuts you can press with only one hand (no three-finger combinations across the keyboard).
You also don't want to click on more icons and buttons than you want to -- your cursor should stay on the canvas as much as possible. So if you don't know the shortcuts for the basic tools, you'd better learn them now. You'll be glad you did. Very useful shortcuts for this tutorial are (by default) a for the Airbrush and Shift+E for the eraser. You'll also be helped a lot by knowing Ctrl + left-click for picking an existing colour from the canvas (this means you don't have to go to the palette). I also recommend learning or even changing the default shortcuts for the Zoom in/out so you know where they are and are placed next to each other. Other critical shortcuts are Ctrl+a and Ctrl+Shift+A for selecting/unselecting all (very useful if you suddenly don't seem to get any results when painting, this often is because of a mistaken selection somewhere), and Page Up/down to switch between layers. There are many more, but that's up to you and depends on your personal preference.
For more details on specific tools useful for digital painting, continue on to the next sections.
2a) Setting up the painter's tools: Some useful brushes
A parametric brush is a brush that is described by a mathematical formula, not an image (also called a "vector brush" in some places). They are created using GIMP's inbuilt brush editor. What we want to do is to create a bunch of useful defaults then set them up so we can rescale them on the fly, using a keyboard shortcut.
If you have GIMP2.4 or later, there are two ways to rescale a parametric brush using the keyboard. The first thing is to change the "Parametric brush size" (which changes the brush itself) and the second is to change the "brush scale", which is a slider in the tool options and rescales any brush to a multple of its original size.
We will set up our parametric brushes to use the first method, as there are two main advantages to it:
However, the major disadvantage of parametric brushes is that they can only take simple geometric forms (circles, squares etc), so for more complex brushes, brush scale is the only viable option ... But for most digital painting simple geometric shapes are actually often more than enough. Despite having hundreds of brushes in my brush folders, the simple round hard brush is still the one I use the most. A range of parametric brushes are great to have for any artistic use, just like regular painters always need to have some basic brushes lying around no matter how advanced they are.
You cannot make the existing default brushes rescalable, you have to create new ones in the brush editor. So first choose to create a new round brush with the Brush editor. Make one with maximum hardness. The actual value of the "Radius" is not so important here -- this you will be able to adjust with a keyboard shortcut. This brush is by far my most often used brush, and coupled with changes in opacity and using various tools it can be used for practically any effect if you only have a little patience.
The brush list is ordered alphabetically. The brushes you create now will likely be your standard brushes in the future, so save them with names starting with aa, so you know it will end up at the top of the list. I saved this first one as "aa_custom1" (if you have many brush sets loaded, you might have to use something like "000_custom1" instead to make sure you end up at the top of the list).
Next create a fuzzy brush by decreasing the hardness value. This is an excellent brush for applying all sorts of effects like smoke and fog. It can also be used very effectively with airbrush or the smudge tool to create perfect colour blends. Save this as aa_custom2, and it will end up next to your first brush.
It can be useful to have a "caligraphic brush" of variable size. Generally the ink tool is better for actual calligraphic work (since 2.4.x the Ink tool can also be resized by keyboard control if it's set up in the preferences). This brush is useful for situations where you need to draw a sharp oblique angle, something which can be hard to do even with a small round brush. I actually have two such brushes, angled differently (angled 45 and 135 degrees respectively). Name them appropriately. You want to have a shorter spacing for this brush, to create a continuous line.
Finally, a square brush. This is very powerful for creating technical forms and structures, like houses, bulkheads and anything that should have a 90 degree edge or corner. Once again, the size (radius) doesn't matter, since the brush will be adaptable. Name it a good name, like "aa_custom5".
2b) Configuring the keyboard shortcuts for brushes
Now to set up GIMP to be able to adjust the brushes quickly. Go into the preferences->Interface->Configure Keyboard shortcuts and choose the "Context" sub-list. This is the context-sensitive setup, which is rather unused in GIMP's default setup.
We begin by setting it so we can change the size of our Parametric brushes.
There are a lot of interesting settings you might want to add keyboard shortcuts to in this menu, but the ones we're interested in for now are the Decrease/Add radius settings.
Assign keys to these by just clicking the entry and then the key-combination you like. My choices are probably not what you'd want to use, since I have it set up for operation with the keys on my tablet. You want to assign keys to all the entries I show in this image. The increase/decrease radius changes the radius of the (user-created) brush by a very small amount, allowing for detailed adjustments. The "Increase/decrease Radius more" steps up in faster steps, which is also very useful sometimes. Finally, if you want precise control, you should use Increase/decrease Radius Relative instead. This adjust radius by percentage instead of fixed step. It is slower to change for small radii, but allows you to precisely tune your radius. Pick keys you think you can reach and use easily with one hand -- that is, the hand you're not holding your mouse in (That is why my Alt++ combination is not suitable for you -- you'll need two hands to put that combo in on the keyboard -- unless you have a tablet with programmable buttons of course).
As mentioned, only parametric brushes can use the Increase/Decrease radius shortcuts, because such brushes are so simple of shape. If you have GIMP2.4 or later, other brushes need to be rescaled with the Brush Scale feature. Go to Increase/Decrease Brush scale and assign shortcuts to them.
Another convenient thing is the "Next Brush" / "Previous Brush" entries, that allows you to flip back and forth in your brush list without actually moving your pointer over there to click on it. This command and the brush resize commands are, next to the zoom, probably the commands you'll use the most during freehand artistic work (is for me anyway), and you'll be hitting those buttons all the time. So make sure you pick keyboard shortcuts that suit you.
Extra hint for GIMP2.4 and later: Newer versions of GIMP has keyboard shortcut entries in the 'Tools' section called "Increase/Decrease Value 1, 2" and so on. If you look at e.g. the tool options for the paintbrush you will see that the first slider is the "Opacity" one. Assigning a shortcut to "Increase Value 1" will change the opacity slider, or indeed any slider that happens to be first in the tool options of the tool you have selected. In the case of the paintbrush, "Increase Value 2" affects the brush scaling. This allows you to create very generic shortcuts, usable anywhere. Another useful shortcut is "Next Object 1,2.."etc. The first such "object" in the Paintbrush tool options is the selector of the currently selected brush. So using "Next Object 1" will flip through brushes, or any of the similar things that appear first. Worth experimenting with. (Thanks to Oion9 for pointing this out)
For drawing tablet users with command buttons and/or touch strip on the tablet: The buttons on the tablet usually work the same as "Ctrl", "Space", and "Alt" buttons on the keyboard (you can configure this separately for the tablet though). Assign these in clever ways to make GIMP do clever things when pressing those buttons (The "zoom" functions are neat to have directly on the tablet for example). If you have a touch strip too, assigning the strip to various button combinations can allow you to change brush sizes, brush types, zoom and even adjust RGB values without having to move your pen off the canvas.
To make sure you can easily see the changing brushes, make sure "show brush outline" is selected in Preferences->Image windows. Also activate the crosshair ("Show paint tool cursor"). The reason for this is because if the brush resizes to becomes very small you might loose sight of it if you don't have the crosshair activated.
Remember to save your settings.
Try it out! Choose one of your self-made brushes and resize it up and down. Step through them with your new shortcut.
This setup will help you when using all common drawing tools that use brushes.
3) Setting up the artistic tools -- about the tools themselves
The primary tools I use for digital painting are airbrush, paintbrush, ink pen, eraser and smudge. Other tools are used as well, but mostly in a supportive fashion, to add some particular effect or minor tweak. Below I will list each tool and what their main uses are. Note that I concentrate on the digital painting aspect here, these tools have many other uses for other types of art.
It is important that you have set up GIMP so that you will see the tool options for each tool as soon as you choose them (i.e. you should not have to double-click to get the options). Without this you will be working blindly.
For tablet users: The "Pressure sensitivity" section of each tool describes the result of pressing the pen down harder on the tablet. For normal use, all boxes are usable (Color is kinda specialized though since it translates the pressure into a position in your currently selected gradient so you might want to wait with that one). It's worth experimenting with (but we won't see any use for this in this tutorial.) The more boxes you have checked, the more involved the respective tool becomes and the more effects you can achieve (since it probably better emulates the real thing) -- but it'll possibly also become harder to handle. Temporarily flipping on/off especially opacity and/or hardness is often useful when wanting to create varying effects.
3a) Airbrush (default key "a")
This is the tool we will concentrate on in the last section, so if you are only interested in getting started with the painting tutorial, just can just read through this and skip over the other tools.
The real-world airbrush is a pen-looking device that holds colour in a little cup and pushes it as an aerosol through its nozzle by use of a stream of air from a compressor. The effect is in some ways similar to that you get from a spraycan, but a professional airbrush allows minute control of spray size and flow rate by tilting and turning a knob on the top of the pen. A notable master of the airbrush is HR Giger.
While most think the airbrush should only create "fuzzy" shapes, this really comes down to how small the spray is and how much flow goes through it; it is capable of needle sharp lines if required.
In GIMP, the amount of colour flowing through the (virtual) device is controlled by the Rate and Pressure sliders at the bottom of the tool options. Choose some decent Rate and Pressure, use my values if you want. This is much a matter of testing out things. Go with my settings if you like. Note the 50% opacity set for the tool. This is a very useful setting and personally I never use the airbrush with any higher opacity than this (rather I'd go even lower, actually). Using the paintbrush with a fuzzy brush (like the one we created in the previous section) is a sure way to make the outcome really fuzzy.
The airbrush tool is excellent for colour blends of all sorts, but by varying the rate and pressure it can be used for essentially the same things as the paintbrush.
Paintbrush (default key ''p")
Everyone has probably used a paintbrush at some point in the real world. It's one of the most flexible paint tools available and capable of creating any effect. Most classical art is done with different forms of paintbrushes.
In GIMP, the paintbrush behaves like a simpler form of airbrush and tends to put down more opaque colours. It is different from the Pen tool (which we will otherwise not cover here) in that it smoothes the edges of its strokes so they look even (antialiasing). If you ever want to do smooth transitions, it extremely useful to use the tool with a low opacity (50-70%).
The brush tool is powerful for creating structure and details in images, as well as in covering large areas in colour. Constantly changing brush type and size is often needed.
Ink pen (default key 'k')
Whereas most think of caligraphic pens as the classical feather quill, the modern artistic ink pen is generally a metal nub which attaches to a generic wooden shaft. These nubs are cheap to buy and their shape and size vary greatly, from flat and wide to narrow to curved depending on what style of line is needed. They are dipped in ink and the ink will fill a hollow on the top of the nub, travelling down to the tip along a split in the nub tip.
GIMP's ink pen tool is in many ways far superior to the original since the control over nub and ink flow is so much more precise and problems like ink spill does not exist. The "Shape" in the tool options control the shape of the nub tip and how it is angled towards the paper. You can also set this to various shapes. The various sliders are of interest since they "dynamically" changes the angle, tilt and size of the tip, just like on a real pen. For a mouse user this is of interest, but rather unwieldly to change on the fly (In GIMP2.4 you can however assign keyboard shortcuts to all sliders from the Preferences->Interface->Configure Keyboard Shortcuts->Tools menu if you are really serious about inking).
For tablet users: Setting the sliders will affect how sensitive the pen is to the input from the tablet. If you happen to have a tablet with tilt sensitity, such as the Wacom Intuos 3, the pen will also detect that and react pretty much like a real ink pen would.
The ink tool is excellent for creating outlines of any type, as well as creating sketches and shapes or even text (although most find that hard to do with a mouse). The varying shape and size of the lines give a dynamic feel that is often used for example in comic books. I'd say it is most often used with a 100% opacity, to create clear, crisp lines (as always this depends though).
Eraser (default key Shift+E)
The eraser is another tool everyone has used in real life. In GIMP its main functionality is however not to erase immediate mistakes (that is what the Undo function is for), but as a paint tool in its own right. The eraser creates negative spaces by removing and thinning existing colour and whereas it can of course be used for corrections it can also be used to create interesting effects. A common use is to "thin" a very strong colour to make it stand out less. For such operations it is often important to use the tool with a low opacity (30-50%) for more flexibility. The only time the opacity should be at 100% is usually when one really wants to delete something completely.
Smudge tool (default key "s")
The real-world equivalent of the Smudge tool is to put a finger in wet paint and pull it out over the paper. This is an exceptionally useful but also extremely dangerous tool because whereas it can create wonderful blends and effects it can also ruin carefully designed images by making them look, well, smudgy.
The smudge tool should generally not be used at 100% opacity, this will literally just smear paint all over without much control (unless that's the effect you want, of course). The lower the opacity, the more subtle the effect will be but the more you have to click and drag to move the colour anywhere.
Almost never is the smudge tool used on its own. Its primary use is to blend fields of colour together in a subtle way. With low enough opacity, a rotating motion can be used to do this (too high, and a whirlpool is created instead).
These tools are also of interest, but are mostly used briefly and for specific things
Clone tool / Perspective Clone tool The foremost use of this tool is to apply texture to the image by use of a source image somewhere in the layer stack. Most often it should not be evident a texture has been applied; Applying with a low opacity and on an "Overlay" mode layer will often create subtle effects.
Blur tool For large images this tool is of rather limited use since its effects are rather hard to detect. It applies a blurring under the brush, allowing things to look smoother. Generally the smudge tool is much more efficient for this, but if you want a perfectly even blur it might be useful (or you might just select the edge and run a blur filter on it ...)
Dodge/Burn tool This applies the dodge or burn operation under the brush. It can be used for shadows and highlights if you want to enhance specific features on a small area. Generally applying shadows on a separate layer (which could be set to burn for example) can be more efficient though since it allows more flexible modifications.
Pen tool This works like the paintbrush except it does not use antialias which means the lines you draw will be pixellated. Useful for certain types of sprite images or icons, but not if you want to emulate real painting.
Fill tool Most often used to fill the canvas with a certain colour, it is also often used by artists working in more "blocky" or "comic" styles to fill blocks of selections with a homogenous color.
Gradient tool In many ways this works the same way as the Fill tool except it fills with a gradient rather than a solid colour. You can select the gradient from a list or make one of your own in GIMP's gradient editor. A nice example use for this is to create beams of light or nice blue skies.
4) Starting out with artistic use of GIMP using the airbrush tool and adjustable brushes
Now let's use these tools and brushes we just set up and learned about to do something practical. The next few exercises should hopefully get you more acquanted with the airbrush tool and how it can be used for artistic work. It takes some practice to use the mouse (or tablet, for that matter) to draw on the computer.
Choose the airbrush tool by pressing the right key on your keyboard. ("a" by default).
Best is if you open the image above in a separate window/tab so you can see the details of each airbrush stroke while reading below. Then try to repeat and practice each step as much as you can. Your hand on the mouse will quickly become steadier, you'll see.
Begin by picking a red tone and the hard-edged brush. Do straight lines vertically and horizontally, in a grid pattern. Try to make as straight lines as you can. Depending on how steady a hand you have, it can be hard to do this with a mouse, but moving it upwards is often easier than going horizontally. Notice how the colours will grow darker in the intersections -- you have colour scaling even without picking a new colour from the palette! Scale down the size of the brush by pressing the keyboard shortcuts you chose before and try it again. Notice how fine and sharp the lines look, despite using the airbrush tool. Try to make the lines as straight as possible, not crooked as I did.
Observe: Of course you could also use the Shift-click/Shift-drag combo to create straight lines. But the point of this exercise is NOT to teach you how to draw straight lines per se -- but to help you get steadier with the mouse (and learn the peculiarities of the airbrush doing so). Learning to master your mouse to draw straight lines "freehand" is an important step towards eventually handling more complex shapes and curves. Freehand drawing skills helps both when doing selections and gives that loose natural look you need for "artistic" style work as we will do last in this tutorial.
When you feel confortable drawing horizontal and vertical lines with the mouse, try drawing them to an angle. Still try to make each as straight as you can. Note how you can overlap the lines several times and the colour will only become richer and richer. Try to work with a lower opacity set in the Airbrush tool if you want, so you can see the effects.
Next pick a blue colour and the "fuzzy brush". Do the same with this brush, to get a feel for what it can do. Once again, notice how the smallest resized brush in blue still appears rather sharp to the eye.
The "Caligraphy brushes" I tested in two tones of green in the image. They are special in that they change size depending on in which direction you draw them. They work well for creating sharp angles and, they can be used to create fuzzy effects, something which the Ink tool cannot do. Try to do some scribbles in green as I have done to get a feel for them.
Finally, the square brush. I used orange for this. Try to create sharp angles and corners with it. Resize and play around.
Finally, try to mix three colours with the airbrush. Pick a clean red and scribble with a large brush. Note how the colour changes and that you don't have to choose any new colour in order to get a lighter red -- just avoid painting over certain areas more than once or twice to retain a lighter tone. Do the same with Blue and Green and make them overlap here and there to see it shine through. (Admittedly I also smudged the center together in my image, to mix even more). The important point here is noticing the amount of different shades you are getting while only choosing three colours from the palette and essentially using but one single tool being pulled back and forth over the same area over and over.
Now try to use the resizing during drawing. Draw a line, resize, draw the next line. Try to do it faster and faster until you have the feeling in your hand.
Finally we'll try some rough sketch with the airbrush tool, using 3 colours only. We will create a dead tree. This is just a sketch, so don't go about deleting or undoing anything you draw, even if it looks odd. Just play with sweeping the airbrush in straight lines, using whatever lines you happen to put down.
Pick a faint pink and fill the background with that using the fill tool.
Then take the hard brush we created and size it up a fair bit. Choose a bright blue colour. Only use that one color from now on, don't pick any other shades of blue -- let the airbrush handle shading for you.
Sweep out vertical lines, just as before, just draw more lines in the center than at the edges, so it'll become darker. Resize the brush and pull out some other straight lines for the branches. Resize the brush as you get further and further out on the branch to make smaller and smaller twigs.
With a rather small brush, make some parts of the trunk sharper, along the edges for example.
Finally, pick a white colour (the 3rd colour we'll use) and with small strokes you apply white at strategic places to bring out parts of the trunk and branches. Copy my lines if you want, but remember this is just a sketch, so don't worry about details. You can use this as a base to create detail later if you want -- but that's another tutorial.
Using the mouse to draw takes practice, but that practice is as much a matter of having a steady hand than anything else. Doing simple things as just drawing straight lines over and over will quickly improve your skills. Curved lines is much more difficult, but can be done too, even though this is where a drawing tablet really starts to shine. Note that you can do a lot with straight lines though, essentially a curve is nothing more than a lot of straight lines if you just use the zoom tool enough ... The tree you should actually be able to do with just straight lines (this is why I picked that example).
Try to make the dead tree for yourself, and show your results!
Was this tutorial too easy for you? Or do you feel you've mastered the airbrush by now?
There is now a second tutorial covering more advanced airbrushing techniques, you can find it here.
Other Art tutorials by me (few of them at least):
Adding light and mood,
Paint a futuristic city,
Draw an eye in 5 minutes (video)
Full list of GIMP art tutorials by me
EDIT: To show an example of what can be done developing such a simple sketch, I added some more to it (very quick thing, mind you):
The Mode drop-down list provides a selection of paint application modes. As with the opacity, the easiest way to understand what the Mode setting does is to imagine that the paint is actually applied to a layer above the layer you are working on, with the layer combination mode in the Layers dialog set to the selected mode. You can obtain a great variety of special effects in this way. The Mode option is only usable for tools that can be thought of as adding color to the image: the Pencil, Paintbrush, Airbrush, Ink, and Clone tools. For the other brush tools, the option appears for the sake of consistency but is always grayed out. A list of modes can be found in Section 2, “ Layer Modes ”.
In this list, some modes are particular:
Figure 13.34. Dissolve mode example
For any paint tool with opacity less than 100%, this very useful mode doesn't draw transparency but determines the probability of applying paint. This gives nice patterns of dots to paint-strokes or filling.
Figure 13.35. Painting in Dissolve mode
Figure 13.36. Example for layer mode “Behind”
This mode applies paint only to transparent areas of the layer: the lower the opacity, the more paint is applied. Thus, painting opaque areas has no effect; painting transparent areas has the same effect as normal mode. The result is always an increase in opacity. Of course none of this is meaningful for layers that lack an alpha channel.
In the above example image, Wilber is on the top layer, surrounded by transparency. The lower layer is solid light blue. The Bucket Fill tool was used, with the Fill Whole Selection option checked and the entire layer was selected. A pattern was used to paint with the Bucket Fill tool.
Figure 13.37. Painting in “Behind” mode
Figure 13.38. Example for layer mode “Color erase”
This mode erases the foreground color, replacing it with partial transparency. It acts like the Color to Alpha filter, applied to the area under the brushstroke. Note that this only works on layers that possess an alpha channel; otherwise, this mode is identical to Normal.
In the above example image, the color of the Bucket Fill tool was white, so white parts of Wilber were erased and the blue background shows through.
Figure 13.39. Painting in “Color Erase” mode
The Opacity slider sets the transparency level for the brush operation. To understand how it works, imagine that instead of altering the active layer, the tool creates a transparent layer above the active layer and acts on that layer. Changing Opacity in the Tool Options has the same effect that changing opacity in the Layers dialog would have in the latter situation. It controls the “strength” of all brush tools, not just those that paint on the active layer. In the case of the Eraser, this can come across as a bit confusing: it works out that the higher the “opacity” is, the more transparency you get.
The brush determines how much of the image is affected by the tool, and how it is affected, when you trace out a brushstroke with the pointer. GIMP allows you to use several different types of brushes, which are described in the Brushes section. The same brush choices are available for all brush tools except the Ink tool, which uses a unique type of procedurally generated brush. The colors of a brush only come into play for tools where they are meaningful: the Pencil, Paintbrush, and Airbrush tools. For the other brush tools, only the intensity distribution of a brush is relevant.
This option lets you to modify precisely the size of the brush. You can use the arrow keys to vary by ±0.01 or the Page-Up and Page-Down keys to vary by ±0.05. You can obtain the same result if you have correctly set your mouse-wheel in the Preferences. See How to vary the height of a brush
The Pressure Sensitivity section is only meaningful if you are using a tablet: it allows you to decide which aspects of the tool's action should be affected by how hard you press the stylus against the tablet. The possibilities are opacity, hardness, rate, size, and color. They work together: you can enable as many of them as you like. For each tool, only the ones that are meaningful are listed. Here is what they do:
The effect of this option is described above.
This option applies to brushes with fuzzy edges. If it is enabled, the harder you press, the darker the fuzzy parts of the brush will appear.
This option applies to the Airbrush, Convolve tool, and Smudge tool, all of which have time-based effects. Pressing harder makes these tools act more rapidly.
This option applies to all of the pressure sensitive brush tools. If the option is checked, then pressing harder will increase the size of the area affected by the brush.
This option only applies to the painting tools: the Pencil, Paintbrush, and Airbrush; and only if you are using colors from a gradient. If these conditions are met, then pressing harder causes colors to be taken from higher in the gradient.
This option causes each stroke to fade out over the specified distance. It is easiest to visual for painting tools, but applies to all of the brush tools. It is equivalent to gradually reducing the opacity along the trajectory of the stroke. Note that, if you are using a tablet, this option does not change the effects of brush pressure.
You know “spacing” in brush strokes: strokes are made of successive brush marks which, when they are very near, seem to draw a continuous line. Here, instead of being aligned brush marks are scattered over a distance you can set with the slider.
Figure 13.40. “Jitter” example
The Incremental check-box activates incremental mode for the tool. If it is deactivated, the maximum effect of a single stroke is determined by the opacity, and moving the brush repeatedly over the same spot will not increase the effect beyond this limit. If Incremental is active, each additional pass with the brush will increase the effect, but the opacity can't exceed the opacity set for the tool. This option is available for all brush tools except those which have a “rate” control, which automatically implies an incremental effect. See also Section 2, “ Layer Modes ”.
Figure 13.41. Gradient options for painting tools.
Instead of using the foreground color (as shown in the Color Area of the Toolbox), by checking the "Use color from gradient" option you can choose to paint with a gradient, giving colors that change gradually along the brush trajectory. For basic information on gradients, see the Gradients section.
You have several options to control what gradient is used and how it is laid out:
Here you see a display of the current gradient. Clicking on it brings up a Gradient Selector, which will allow you to choose a different gradient.
Normally a brushstroke starts with colors from the left side of the gradient, and progresses rightward. If "Reverse" is checked, the stroke starts with colors from the right side, and progresses leftward.
This option sets the distance corresponding to one complete cycle through the gradient colors. The default units are pixels, but you can choose a different unit from the adjoining Units menu.
Figure 13.42. Illustration of the effects of the three gradient-repeat options, for the “Abstract 2” gradient.
This option determines what happens if a brushstroke extends farther than the Length specified above. There are three possibilities: "None" means that the color from the end of the gradient will be used throughout the remainder of the stroke; "Sawtooth wave" means that the gradient will be restarted from the beginning, which will often produce a color discontinuity; "Triangular wave" means that the gradient will be traversed in reverse, afterwards bouncing back and forth until the end of the brushstroke.
How to Use Airbrush Tool
* Airbrush toolis used to paint the image with a variable pressure.
* This tool is the convenient tool to paint an image.
* It can be regarded as the traditional airbrush.
* It suits well to paint the smoother areas of color.
* When compared to the paintbrush tool, it is slightly difficult to operate/handle.
How to Launch:
- Open Gimp.
- Launch a new file.
- Now pick Airbrush Toolfrom the toolbox.
* To select, click the Toolbox and then press the button A(shortcut).
Mode- The list of 23 options enables you to modify an image with different options.
Opacity- This option increases the strength of the tool and also makes the background of an image vague when the image is brushed.
Brush- This option provides you various types of brushes or shapes to paint the image.
Scale- This option is used to maximize or minimize the size of the Airbrush tool.
Brush Dynamics- The Pressure, Velocity and Randomfeatures are mixed with the Opacity, Hardness, Size, Rate and Colorto offer a different feature to the tool.
Fade Out- This option makes the airbrush to give a paler effect to the paint that has been applied on the image i.e. the color painted turns fader.
Apply Jitter- This option is used to spread a variety of colors on the image which makes the picture so attractive.
Use color from gradient- This option provides you with plenty of Gradienttypes or color patterns, which helps you in drawing on the image.
Rate- It configures the speed of the color application. Maximum level of rate will exhibit sharp and dark brush strokes.
Pressure- This option determines the level of pressure - whether to be high or low. The effect of this option can be felt when it is applied on an image.
How to Use:
- Open a new file.
- Note that this tool simply helps in painting and to apply colors to an image file.
- It would be effective when the additional brush or shapes are added to this tool.
- First decide the color to be used to fill the image.
- Set the options and apply it on new file or even on image files to acquire a new designed image.
- At last, click "File -> Save" to "Save" the file.
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