Gimp Original Tutorial

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Tutorial

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TUTORIALS

Beginner

GIMPLite Quickies Use GIMP for your graphics needs without learning advanced computer graphics methods.

Simple Floating Logo The famous "GIMP Floating Logos" rescued from the original GIMP web site and slightly modified to fit here. Even if you hate images of text on the web, this tutorial gives you some of the basic layer manipulation techniques. The knowledge can be applied to many many imaging projects and the logo *is* pretty cool ...

Draw On Selections Borders Use the selection tools to draw simple or complex shapes. Paths (Bezier Selections) Use paths (bezier curves) like the GIMP Masters do.

Quickmask Use Quickmask to make a vignette of your photos.

Red Eye Removal Use the Channel Dialog in one method of removing red eye from photos. Straight Line Tutorial 'Tis somewhat rude. Perhaps the exact right frame of mind which to approach GIMP with though, at least the first few times ....

Intermediate

Drawing Shapes With Paths Make a dimensional box with paths (bezier curves) and gradients. Anti-Aliased Threshold Use curves and modes to transform your photo into a pen and ink watercolor like image.

Film Grain Give your photos the appearence of film grain and learn about a new mode.

Changing Background Color 1 Change the background color of your image and learn the magical properties of color2alpha.

Changing Background Color 2 Change the background color of your image and learn the magical properties of Select By Color.

Coloring A BW Sketch Color sketches anime style.

3D Floating Logo Another GIMP Floating Logo method, this one uses modes along with layers and select tools.

Tileable Textures Learn about gradients, animated brushes and how to make tileable images as well. Simple Animations Learn how to work with GIMP's layers as animation frames.

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Expert

Make GIMP Image Pipes Rank and Dimension. GIMP's Image Pipes can do alot.

Make GIMP Image Pipes 2 Even more options for pipe creation.

Golden Text Make beautiful golden text and learn about the curves dialog and other color options.

Sketch Effect Change your photo into a normal sketch.

Photo To Sketch Change your photo into a nice painting or sketch.

Draw A Paint Brush Put it all together and work your GIMP like the masters do.

Creating Icons Use GIMP to create nice icons.

Using GAP Learn the basics about using GAP, GIMP Animation Package.

Advanced Animations Learn how to make an animation with GAP.

Photo Editing

Color2BW Converting Color Images to B&W.

Selective Colorization Convert images to black and white and restore color selectively.

Reducing CCD Noise Learn how to reduce the CCD Noise in photos.

CCD Noise removal Use selective Gaussian blur to remove CCD Noise in photos.

Contrast Mask Decrease problem contrast in photos.

Sepia Toning Create a nice sepia photo from color images.

Gaussian Blur Overlays Increase saturation and add a "dreamy" feel to your photos.

GIMP Surgery "patch" blown out hightlights in your photos.

Blending Exposures Increase dynamic range by combining different exposures of the same scene.

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Web

Perlotine Get your image in place with the help of perlotine and tables.

Image Map Use GIMP to create a nice Image Map.

Script Authoring

Working With The Image Before you script, know what an image is and isn't and what a drawable is. Or at least be able to take a good guess about it ...

Basic GIMP Perl Learn how to write simple perl scripts using the gimp-perl module (GNU/Linux users only).

GIMP-Perl Debugged Ways to debug your gimp-perl scripts.

GIMP Batch Mode A basic instruction about batch mode and GIMP.

GIMP Script-Fu Write Scheme for GIMP.

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GIMPLITE QUICKIES

Intention

So, you have GIMP installed on your computer, you need to make a quick change to an image for some project, but don't want to learn about computer graphics right now in order to get the image changed. Totally understandable. GIMP is a powerful image manipulator with many options and tools. However, it is quick and somewhat intuitive (after a time) for the small jobs as well. Hopefully, these quickies will help you with your quick problem and help you to stay friends with GIMP and ready for its more complex tools and methods later, when you have the time and inspiration.

A couple of words about the images used here. The came from APOD, Astronomy Picture Ofthe Day. The screenshots were taken on my desktop which is sporting this APOD image.

All you should need to know to start here is how to find your image and open it. File -> Open.

Change the Size of an Image (Scale)

Problem: you have a huge image and you want to put it nicely for viewing on a web page. GIMP is a quick solution. Our example image is this beauty m51_hallas_big.jpg from APOD.

The first thing that you might notice is that GIMP opens the image at a logical size for viewing. So, if your image is really big (like the sample image) it will display it zoomed out until it fits nicely. You can tell if GIMP has done this by the percentage number in the title bar. (you can click on the little screenshot to see the full view of the screenshot) Just because it looks right in this "View" doesn't mean anything.

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Image entry in the menu and the sub menu from the screenshot should reveal itself. Click on "Scale Image...". When ever you click an option from the menu that has ... behind it, expect another dialog. This time, you should get the "Scale Image Dialog".

If you have a desired width, put it in the dialog at the top where it says "New Width". If you don't have such a number in mind, you can steal the width of GIMP's default image size, which is 256 pixels. This is demonstrated in this screenshot. You can see the image that this scale dialog produced here.

Perhaps you want your image to look more like a 4x6 inch photo on most image rendering web browsers. Simply switch the units to "inches" and put 4 inches in the height box (opting for smaller than 4x6 rather than bigger). You can see this dialog here. The image this dialog produced here.

Let GIMP choose the other dimension length for you. Meaning, it will take more image knowledge to change both width and height and have it look correct. So only change one and let GIMP change the rest. To change the other length see the crop quickie.

Make jpegs Smaller

You can make your jpegs smaller without changing the pixel width of the image. Actually you can change the weight of the image a lot. I used an(other) image from APOD. The original image is huge (3000 pixels wide) so I also made a smaller (pixel width) image available. To prepare this image for the web, you should first reduce the image to a better width and height for web viewing as described in the scale quickie. Right click on the properly scaled image and follow the menus <Image> File -> Save As.... The Save Dialog will pop up.

I generally type the filename I want into the text box, but the Extension drop menu can tell you the available file formats (depending on the libraries you have installed and the conditions of the image you are trying to save). If GIMP complains right now, or if "JPEG" is grayed out in the Extensions menu you should just cancel out of everything and step through the Change the Mode Quickie.

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In the JPEG Save Dialog, you can opt for GIMP defaults which reduce the size quite a bit, without hurting the visual quality in a way that I can detect. This would be the safest and quickest thing to do.

If you would like to make it smaller still, make sure that the "Preview" toggle is on and then watch the image area and change the compression level by moving the "Quality" slider down. You can see the quality of the image changing, especially towards the leftmost end of the slider. Here is a screenshot of me doing this very thing. As you can see, very small is also very bad. I have a screenshot of me setting the Quality slider to a more acceptable level here.

I have not been showing the actual jpegs I created so that we could end this quickie with a race. Clicking this page should "race" these jpegs to a web page (the first time you see an image in most browsers, you are also waiting for it to write to the cache, so the first time is the worst). With my cable modem, I was unable to see a difference in the load time, but the difference in what you actually see is fairly interesting.

Crop An Image

Many reasons to need to crop an image. Making rectangles square, or making squares into rectangles. Cutting alot of useless background to bring out the subject better. etc. To get to the crop tool, you can either push the button on the toolbox or right click on the image and follow the menu <Image> Tools -> Transform Tools -> Crop & Resize. This will change the cursor and allow you to click and drag a rectangular shape. The button in the toolbox is the nicest way to get to any of the tools. I have chosen one of the huge and beautiful APOD images, ngc6369 heritage.

I always click on the approximate upper left corner and drag to the lower right corner. You don't need to worry about being accurate on this first swipe with the crop tool, since a little dialog will pop up and you can make a better choice for your new borders there..

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After completeing the click and drag motion, a little "Crop & Resize Information Dialog" (shown above also) pops up, telling you information about the borders that were defined in the click and drag. We will have to change all of the numbers. If you would like to make this rectangular image square, you should find the width and height from the Get Image

Information Quickie. Use the smallest of the two lengths to determine the size of the square. In my 300 x 225 pixel image, the largest square I can get is 225 x 225 pixels, and I will need to make sure the Y origin is 0. At that point, I use the image and the squares to get the best part of the image for the area. The upper right and lower left crop squares will move the marked area. The other two (upper left and lower right) will change the dimensions of the marked area, so be careful. I have a screenshot of this, right after I fixed the width and height and the Y origin, but before the final positoning. The arrows show the move points.

I decided that the image looked the best with the X Origin at 42. The final image appears here.

Find Info About Your Image

This window will tell you the pixel lengths. Right click on the image and follow <Image> View

-> Info Window... Here is a screenshot of a calculator which also gives lots of good

information. I got another image from APOD It is pretty big. (Not as big as Saturn though) You can see in the dialog above, it is 2241 x 1548 pixels.

If you are just making a square out of a rectangle, like in the Crop An Image Quickie, you need only to open the dialog and find the lesser length and use that as described. Since this is very little information, and definately not enough to fill the space between the menu thumbnail and the dialog screenshot in my layout, I thought I would run through some calculator exercises that might help you to meet your image needs.

It is nice to have images appear on a browser window as a photo would. Photos online appear to be 4x6 inches when scaled to 288x432 pixels (72 dpi for many monitors). There is a

problem, however, if you try to scale this image. The ratio of width to length of the original does not match the ratio of the photo. So, to make the scaled image the correct size crop 10 pixels from the height. For the sample image, it was best to crop 10 pixels off from the top. The final image should "appear" as a 6x4 inch photo on most monitors.

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There will be problems whenever mixing scanned photos with digital photos and also with scanned negatives. Modern film developing machines automatically crop one half of an inch off from each image -- the rumor is that the photo printing machines match a certain style of camera view. If you are preparing an image to be printed on a machine like this; or if you are planning on a gallery where the images are from different sources, some intelligent cropping to fit the best size for the medium you have chosen will be a plus. If this is confusing; please blame the photo printing industry and not GIMP.

You can change the Resolution of your image as well, using the same methods as we used in the Scale, although, in my somewhat limited use, the issue is more about how many pixels. Let's say you want to get this image printed at the photo lab. 300 pixels for every inch is preferred. This original image will print easily as a 7 x 5 photo. 2241px/300ppi = 7.47in. Get out your calculator for the short side. 1548/300 = _.

There is another brutal fact you should come to terms with if you are new to graphics and computers. Just because it looks good on the screen (the image from before) doesn't mean that it will print that nicely. I tried to emulate how this image would appear printed at 300dpi here. Sorry. There are some options, for instance my friend printed images and then scanned them back in. Terrible business!

Change the Mode

As with anything else, images come in different kinds and serve different purposes.

Sometimes, a small size is important (for web sites) and at other times, retaining a high colour depth in all its glory (a family portrait) is what you want. GIMP can handle all of this, and more, primarily by converting between three fundamental modes, as seen in this menu. In order to switch your image to one of these modes, you open it and follow that menu and click the mode you want.

RGB - This is the default mode, used for high quality rich colour images. This is also the mode

to do most of your image work with including scaling, cropping and even flipping as it gives the computer more information to work with. This extra information also makes RGB Mode the largest to store as a result.

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A little bit of detail if you are interested. Each pixel or point when in this mode consists of three different components. R->Red, G->Green, B->Blue. Each of these in turn can have an intensity value of 0-255. So, at every pixel, what you see is an additive combination of these three components. All these combinations result in a way to represent millions of colours.

As an example to practice with images have been provided in various sizes and formats. Indexed images of different sizes: from a very old APOD a small gif and a larger gif of the same image from a later APOD. Also the same image in RGB as provided by Earth Observatory a smaller version and a huge version.

Indexed - This is the mode usually used when file size is of concern, or when you are working

with images with few colours. It involves using a fixed number of colours, 256 or less, at each point to represent the colour at that point. GIMP defaults to attempting to figure out an "optimum palette" to best represent your image. Try it, you can undo it if you don't like the results, or use a custom palette or more colours.

As you might expect, since the information needed to represent the colour at each pixel is less, the file size is a lot smaller. However, sometimes, there will be options in the various menus that seem to have been "greyed" out for no apparent reason. This usually means the filter or option cannot be applied when your image is in its current mode. Changing the mode to RGB as outlined above should solve this issue. If that doesn't work either, perhaps the option you're trying requires your layer to have the ability to be transparent. This can be done just as easily via (Image)->Layer->Transparency->Add Alpha Channel.

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Grayscale - In case you want to convert your brilliant colour image to something that's black

and white (with a lot of shades of grey), this is one of the easiest ways in which to do it. Some photos do look a lot fancier when displayed in grayscale. Again, if you're interested in some detail, this is achieved by taking the RGB values at the pixels in your image, and suitably weighted averaging them to get an intensity at that point.

There is no need to convert an image to a specific mode before saving it in your favourite format, as GIMP is smart enough to export.

Flip An Image

When you need the person in the photo looking in the other direction, or you need to top of the image to be the bottom. Mirroring the image (sort of). Right click on the image and follow the menus <Image> Tools -> Transform Tools -> Flip, or use the button on the toolbox. Using another APOD image I demonstrated all of the flips on this image. You might get bored

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The tool used as is (the default) will do this to an image.

If you double click on the button, up will pop the means to flip images vertically as well. I did just that on this image.

For a really big finish, I flipped this image both ways. At least it is such a cool image for all of this silliness.

The flips are all displayed on one page for you, here. One might ask themselves, useful? or filler for a pre-established format?

Rotate An Image

Let's say you turned your brand new digital camera to get a vertical shot, now some of your images are on their sides. Right click on the image, and follow the menus <Image> Image ->

Transforms -> Rotate -> 90 degrees (or 270 depending on the orientation). Using an APOD image. I rotated it once to demonstrate. 90 degrees CCW.

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THE BASICS TUTORIAL

Intention

On this page, the first section of our ever growing (?) collection of tutorials, I will demonstrate the basic operation you will need to perform over and over again in your life as a computer artist: Generate isolated parts of a picture and combine them with a random background. What we want to achieve in this example is to generate a 3-dimensional text logo flying (and movable) over the background (a simple uni-color layer in our case, but you will easily see that you could use any other (stack of) layers/images instead. Start with a plain white picture, black as the foreground color and open the layer dialog!

Adding text

Use the text tool to add some text. You will get a new text layer which you can also see if you look at the layers dialog. You can use the move tool to move the text where you like to have it. Then merge it with the white layer below by choosing Merge Down from the Layer menu. You should now have one layer with black text on white background. Using <Image> Layer ->

Colors -> Invert you will achieve something like the picture above.

Adding colors

First of all: Blur the image a bit (Gaussian blur at 5 may be a good start). Now add a new layer to the image with the help of the New Layer button in the layers dialog. Choose it to be white. It will be created above the just made text layer effectively hiding it. It will be active which can be seen from the fact that it has a blue background in the layers dialog. Click some times on the eye symbol to see how you can make a layer invisible and make the other layer active by clicking on its small preview in the layer dialog. At the end, leave the new white layer visible and active. Use the plasma plugin to make this layer a little colorful (Yes, you are invited to experiment with the parameters...). The layer dialog should look something like this now:

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Bumpmapping

It's getting funny now: Use the bumpmap plugin with the blurred text layer as a bumpmap on the plasma layer. You can play with the other parameters, but they have sensible defaults. You'll get an image like the one above. Now (still on the plasma layer) choose Add layer mask from the layer dialog menu. Choose the mask to be white. Nothing will change on the image for now, but the layer dialog will look like this:

You can toggle whether a layers mask or the actual picture is active by clicking on their previews in the layers dialog.

Using the layer mask

Now activate the text layer again. (you don't have to make the layers on top invisible to work on this layer. It's enough that you activate it in the layers dialog.) Now do <Image> Edit ->

Copy. Make sure you have the mask of the top layer selected and the layer is activated.

Choose <Image> Edit -> Paste. You will again get a floating selection, shown in the layer dialog like this:

Use the layer dialog menu to Anchor Layer, which will anchor the floating selection into the previous activated layer (which is the mask of the plasma layer in our case). This will leave you with the following scenario:

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Adjusting the levels

Now add a new layer and fill it with some color (e.g. with the help of the bucket fill tool) and use Raise Layer or Lower Layer from the layer dialog menu to achieve something like this:

Now you'll see that the image of the logo isn't very sharp. We'll change this now. Make sure you have selected the plasma layer's mask and open <Image> Layers -> Colors -> Levels. This tool is one of the most important tools you have! Play with the little triangles you'll see in the two grey gradients and watch their effect on the image. For now, try to achieve something like the following:

What we do here is making the border of the mask sharper, and by that means, sharpening the whole picture (the area which is neither 100% opaque nor transparent will become smaller). But we can easily avoid the picture getting pixel-steps by leaving still a smooth transition between opaque and transparent parts of the layer. (If you didn't realize it by now - I bet you did - the layer mask works in such a way that all black parts of the mask will become transparent parts of the layer and all white parts will stay opaque (with smooth transitions realized by values of grey).

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Creating a drop-shadow

Using the layer menu you will have noticed the entry Duplicate Layer. Use this now. Then use Apply Layer Mask and Lower Layer which should leave you with something like this:

Make sure you check the Keep Transparency option (the little box next to the layer mode) and then fill that duplicated layer with black. You can paint over the text with a paint tool or simply drag a black color from the color selector and drop it over the image. You do not have to be careful: the Keep Transparency button will let you paint only on opaque parts of the image. This will give you:

Now make sure you uncheck the button again and move the layer some pixels to the right and downwards. You can move it with the Move tool while pressing Shift so that it moves the current layer instead of picking a new one. (Alternatively, can use <Image> Layer ->

Transform -> Offset and enter a small offset for both X and Y: this will offset the contents of

the layer without moving the layer itself.) Then blur your layer and adjust the transparency with the slider so the background will shine through: You've just generated a so-called drop shadow, which greatly enhances the 3D effect and is used in very many places.

That's it! Now have a lot of fun making flying logos! The original tutorial can be found here.

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BORDERS ON SELECTIONS

Intention

Since GIMP is an image manipulation program and not a painting program it doesn't include tools to draw shapes like squares and circles. However this doesn't mean you can't paint them, in fact there are some interesting options regarding this subject when it comes to GIMP. The solution is to use the selection stroking capabilities of GIMP.

This option can be accesed on the image menu (right button click on the image), by going to

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Step 1

Before doing that however we need to make a selection with the shape we want. There are several ways to make a selection, including all the tools in red shown above and select by color as explained on Selecting and removing one color . When using the tools, holding shift at the beggining of the selection process will add the selection to what is already selected, while holding the control key will substract from it.

Step 2

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Step 3

After you have the selection, choose a brush from the brush selection dialog. Choose also a color and you can play with the spacing option for the brush. Brush selection dialog

Step 4

When all the options are selected you can click on <Image> Edit -> Stroke. You will get a dialog allowing you to set many options for stroking your selection, including dashed lines and other fancy features. If you select Stroke Using a Paint Tool, you will be able to use the brush that you have selected.

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Step 5

When all the options are selected you can finally click on OK. Using a fuzzy brush and selecting a blue color here is the result for the selection made above.

Examples

Playing around with the spacing options in the brush selection dialog, the color or using one of the animated brushes you can get very interesting results.. here are some examples. The original tutorial can be found here.

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SIMPLE PATHS (BEZIER SELECTIONS)

Intention

The Path tool (previously known as Bezier Selection) is a powerful tool in GIMP. The

rectangle- and ellipse-selections are not very flexible if you happen to need something more special. And since many of us GIMPers don't have a graphics tablet, it's not so easy to make the mouse pointer move the way you want. The paths can solve the problem by using smooth mathematical curves instead your own shaky mouse trail. Paths are also very useful when used with gradient fills, see Drawing Shapes with Bezier for more information on this great tool.

What is it?

The Path tool can make complex selections by specifying certain points that are connected together with a curve. So to make a box you would specify four points, one for each corner of the box. Example in image above. The great thing is the corners don't have to be 90 degrees.

In older GIMP versions (1.2.x), you had to close all paths by joining the last point of the path to the first one. This is not necessary anymore in 2.0 and later versions, but this is still useful to create closed shapes such as a box. So after creating the fourth point, press and hold the Ctrl key and click on the first point to close the path. Of course you can have as many points as you need.

Finally, click the "Stroke Path" button (in the Path Options dialog) or use the menu Edit->Stroke Path... to draw the new shape. You can also use the button "Create Selection from Path" if you want to have a selection that you can fill or stroke.

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Modifying the curves

Straight lines alone are a useful thing, but it's not all. Actually they are not lines but curves. Cool anti-aliased smooth curves.

The curves can be modified quite flexibly by adjusting the 'handles' of the nearest points. 'What handles?' you say... See the image above? The small circles are those familiar points we used with the box in the previous section. The little boxes are those handles. The handles are not visible by default, you must drag them 'out' from a point. To make the handles visible 1. click to a point to make it active, 2. while pressing the Ctrl key, click again on the same point and 3. drag the handles out with the mousebutton still pressed down. You notice the curves between the points are not straight anymore. You can control the shapes by dragging the handles around.

A Few Tips

Always before modifying any points or handles, click the handle or a point to make it active.

To have a smooth curve, both handles should be aligned at each point. Press Shift while dragging a handle to ensure that the other one remains aligned.

A path can have multiple components. If you have closed a path, you can create a new component by clicking where you want to place the first point of the new component. If you want to create several components without closing them, press Shift and click where you want to start a new one.

When you are satisfied with the shape, you can use Stroke Path or Create Selection from Path.

The default GIMP installation creates a dock containing the tabs "Layers, Channels, Paths, Undo". Click on the Paths tab to manage your paths.

The original tutorial can be found here.

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Bezier Selection

Bezier selection is a powerful tool in The Gimp. The rectangle- and ellipse-selections are not very flexible if you happen to need something more special. And since many of us gimpers don't have a graphics tablet, it's not so easy to make the mouse pointer move the way you want. Bezier selection fixes the problem by using smooth mathematical curves instead your own shaky mouse trail. Beziers are also very useful when used with gradient fills, see

"Drawing Shapes with Bezier" for more information on this great tool.

What is it?

Bezier selection is a tool to make complex selections by specifying certain points that are connected together with a curve. So to make a box you would specify four points, one for each corner of the box. Example is on the right side. The great thing is the corners don't have to be 90 degrees. After selecting the fourth point, click on the first point to close the curve (beziers have to be closed - at least at the moment in the current Gimp). Finally click inside our 'box' to turn it into a selection. Of course you can have as many points as you need.

Modifying the curves

Straight lines alone are a useful thing, but it's not all. Actually they are not lines but curves. Cool anti-aliased smooth curves.

The curves can be modified quite flexibly by adjusting the 'handles' of the nearest points. 'What handles?' you say... See the image on the right? The small circles are those familiar points we used with the box in the previous section. The little boxes are those handles. The handles are not visible by default, you must drag them 'out' from a point. To make the handles visible

1. click to a point to make it active, 2. click again on the same point and 3. drag the

handles out with the mousebutton still pressed down. You notice the curves between the points are not straight anymore. You can control the shapes by dragging the handles around.

A Few Tips

1. Always before modifying any points or handles, click the handle or a point to make it active

2. To move just one handle and leave the opposite side in its place, click on the handle to activate it and press shift while dragging it

3. To move the points around, activate a point (or its handle) and drag it around with ctrl pressed down

4. When you are satisfied with the shape, click inside the curves to turn it into a selection

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QUICKMASK TUTORIAL

Intention

This tutorial shows how you can do vignette effects using a feature of GIMP called

QuickMask. QuickMask is a convenient way to modify selections using pixel-changing tools such as the paintbrush, eraser, or any plug-in filter. It lets you make very precise adjustments to your selections. This tutorial doesn't use QuickMask for complex masking; it's intended to show how you can use it to create quick and easy vignette effects.

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Step 1

For your first step, load up an image. Any image will do. GIMP 1.1.7, a development version of GIMP, introduced QuickMask. The QuickMask control button is located at the lower-left side of the image.

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Step 2

First, make a rectangular selection around the edge of the image. Then click on the red-bordered QuickMask icon in the lower-left corner of your image.

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Step 3

After you click the red QuickMask button, a translucent red mask appears around your selection. This red mask represents the outside of your selection. When you click the dashed QuickMask button to go back into normal selection mode, anything red will not be selected, and anything clear will be. So, let's start playing with this mask. First, right click on the image and select <Image> Filters -> Distorts -> Waves from the menu. Apply the filter, and watch what happens to the mask.

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Step 4

The mask gets all wavy. Let's add one more effect: <Image> Filters -> Blur -> Gaussian Blur

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Step 5

Now that there is a soft edge on the mask, click the dashed QuickMask button to convert the mask back into a selection.

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Step 6

See how the selection follows the mask? This is a powerful feature of QuickMask. You can use it to modify any existing selection, and you can even use it to create new selections. Our last step is to use <Image> Select -> Invert and <Image> Edit -> Fill with BG Color. The result, a soft white fade into the background, is shown in the final step.

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Final

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Examples

The above image used <Image> Filters -> Noise -> Spread, with horizontal and vertical settings at 11, to get the effect.

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As in the tutorial, this one used Waves, but instead of blurring, I used <Image> Filters > Blur

-> Pixelize instead.

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RED EYE REMOVAL

Editor's note: since this tutorial was written, the Red Eye Removal plug-in has been included in the default GIMP package (see Filters -> Enhance -> Red Eye Removal). This tutorial is still useful if you want to do things by hand.

Intention

It used to be that the photos with red eye weren't really worth fixing as only cheesy cameras had the flash built in and underneath the red eyes was a crappy photo. Well, welcome to the future when you can get a pretty good image from a camera with the flash built in. They do not have a button that works to prevent this yet, so don't even try it. The best way to fix red eye on photos is to have those intense people look at the photographers shoulder. The cause of red eye is the flash reflecting from the back of the eye and into the lens. So, until this lovely child is able to understand "look at my shoulder" it is good to know that red eye can be fixed, somewhat. I learned the following method from tigert while lurking on the irc late late one night.

Step 1

I zoomed in on the image, 4:1 ratio, as this is almost pixel by pixel work. I ended up using the 5 x 5 fuzzy brush that came with the GIMP tarball. As usual, your choice depends on the resolution of your image. A fuzzy brush is highly recommended. On this web sized image, the 3 x 3 fuzzy brush didn't work fast enough. As always, you can <Image> Edit -> Undo until you make the right selections.

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Step 2

A long time ago, someone suggested on the gimp-user list that the Layers, Channels and Paths Dialog always remain open while you use GIMP. Some three years later, I still follow and give this advice. So, if your

Layers,Channels and Paths Dialog is not open, open it and leave it open. Select the Channels Tab. Deactivate the Green and Blue Channels by clicking to the right of the thumbnails in the dialog window.

The image should still look like the screenshot of the close up in step 1. If it looks all red, you have just turned the view of the color off. (burning the red eye area will not work if the Layers,Channels and Paths dialog is set up that way, I happen to know).

Step 3

Make certain you have a good brush selected (for this image I used the 5 x 5 fuzzy) Then select the Dodge and Burn Tool. Double click on the button to get the Tool Options dialog. My dialog defaults to dodge and midtones, for this project, choose burn and hightlights (as illustrated). Touch all of the red in the eyes with the burn tool. I think that I used the burn tool on the midtones just a little bit also. GIMP doesn't have a magic button to fix red eyes with, but it has the tools. It has been my experience that each image is slightly different and I sort of like the control that GIMP gives you ... tigert warned that this method can leave the white spots in the eyes slightly green. I have found this to be true, however so far it hasn't been enough green to worry about. Given a photo where the green

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Final

... looking so much better!

The very best fix, of course would be to prevent it from happening. Due to the nature of the problem, my guess is that it will be the same people over and over again with this problem. Some personalities have no problem looking deeply into the camera lens (like this beautiful baby for instance) and maintaining the gaze through the flash. My guess is that as soon as these people know what is going on, they can fix it themselves.

Other personalities have other portrait problems. There is a small handful of people who have no problem looking into the camera lens, but anticipate the flash and blink at the wrong moment. This causes the portrait to look like the object is starting to sneeze. (this is what happens to me) If you know of a method to prevent this, please email me.

What a cute baby. This is Maurits and his baby. He is one of a growing list of developers that are changing their babies while working on GIMP. I watched work on WinGIMP occuring between diaper changings and feedings also. *chuckle*

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STRAIGHT LINE TUTORIAL

Intention

This tutorial shows you how you can do straight lines with GIMP, using a feature called the Shift Key. Straight lines are a convenient way to make things that aren't so terribly affected by the imprecision of a mouse or tablet, and to take advantage of the power of a computer to make things look neat and orderly. This tutorial doesn't use Straight Lines for complex tasks; its intended to show how you can use it to create quick and easy line effects.

Step 1

The invention called the typewriter introduced the Shift Key. You generally have 2 of them on your keyboard. They look something like the picture on the left. They are located on the left and right sides of your keyboard.

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Step 2

First, create a new image. Any size will do.

Step 3

Then click on the paintbrush. Any of the red-highlighted tools on the above toolbox can do lines.

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Step 4

After you click the paintbrush tool, you can click the image. A single dot will appear on the screen. The size of this dot represents the current brush size, which you can change in the Brush Dialog.

Now, lets start drawing a line. Hold down the Shift button, and keep it down.

Step 5

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After you have a starting point, and have held down the Shift Key, you'll see a line like above if you're running GIMP version 1.2.x or later. This feature was not present in GIMP version 1.0.4. However, the next step works the same way.

Press the first button on the Mouse (the leftmost one usually) and then let it go. During that whole "click" of the Mouse button, you need to keep the Shift Key held down.

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See how the line is drawn on top of the preview? This is a powerful feature of the Paint Brush. You can use it with any of the tools shown in step 4, or even draw more lines at the end of this one.

Our last step is to let go of the Shift key. And there you have it. Some more examples are shown below. Questions? Comments? Let me know.

Happy GIMPing! Seth

Examples

This one I turned on gradient in the Paint Brush Tool.

This one I rendered a grid, and then used the Smudge Tool with a low spacing and a slightly larger brush.

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This one I used the Dodge tool on the top and left of a blue box, then used the burn tool on the right and bottom.

DRAWING SHAPES WITH THE PATH TOOL

Intention

The Path Tool (replacing the old Bezier Selection tool) can be used in many creative ways. Maybe the best thing in it is the smooth, beautiful curves it produces. But you can also use paths to create different polygonal shapes if you don't 'pull out the handles'. Polygonal shapes are especially useful when painting some geometric objects, as you can draw one side at a time (into different layers if you want).

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This tutorial is about making simple geometrical shapes with GIMP. I will concentrate on the Path tool since I find it so useful for this purpose. I hope you get some help and new stuff to put in your GIMP Tricks Sack :) I personally use this technique for nearly all my work.

Notice! This is not a 'back to basics' -tutorial. You should be familiar with GIMP's dialogs and

menus. I was thinking about this, and I did not want to make this an 'entry level' thing, basically to avoid bloating this too big and duplicating other people's work. Paths are covered in my other tutorial, and I recommend you to read it before going further if you find the material here confusing. If you are new to GIMP I suggest you to go to the GIMP homepage in www.gimp.org and first read through the Documentation section there.

Let's get started!

First we must create a new image for our creation. Make the size 256x256 pixels and choose

RGB for the type. The image background should be white. During this tutorial, you will have to

use the Layers tab and optionally the Paths tab from the dock "Layers, Channels, Paths, Undo". This dock is present in the default GIMP installation. You can also get these tabs using

<Image> Dialogs -> Layers and <Image> Dialogs -> Paths.

1. Left side

Now create a new transparent layer, and name it Left_side so you know what layer I'll talk about later on. Make sure you have the new layer active by checking the layers-dialog. If it is not selected, click the layer's name in the dialog.

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Choose the Path tool and make something like the side #1 on the blue cube, think about the perspective. (If this causes you trouble, don't worry. You will learn by experience). You can adjust the points' places if you can't get them right at the first try, see the Path tutorial for more information on that. Your path should look something like the one on the right.

Once you are satisfied with your "box", convert it to a selection using the button "Create Selection from Path" (in the Path Options dialog) or using "Selection to Path" (in the Paths tab).

Next we must choose some nice colors for our gradient, choose white for the foreground color and some dark-blue for the background (we are making a blue box, remember?) Something like that on the image nearby.

Select the gradient-fill tool and, starting from the top-left of the selection, 'drag' the gradient quite far down-right (see the arrow in the image. This way you get a quite light-colored face for the cube, and it is just what we want here. We also want the lighter end of the gradient to be near our imaginative light source. (The light was coming from the left)

2. Right side

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Now on to the right side, side #2. Create a new transparent layer and name it Right_side. Use the Path Tool and try to make the right side of the cube and turn it into a selection.

Take the Gradient Tool again and, still with the same colors, make a gradient from farther up-left to near the selection's lower-right corner (see image on right). This way we get a darker gradient suitable for the shadow-side.

Hint! Be careful with the edges. You don't want to leave any holes so the background can be

seen through... It's better to overlap the lower layer a bit than leave a space between them.

3. Top side

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Now you probably know we want to make yet another path and this time the gradient has to be even lighter than in the first side. So I suggest you lighten the dark blue color a fair

amount, it's easier to get a light gradient that way. This time you pull the gradient from left to right, according the arrow in the picture. Once you find the shading look good, you can flatten the image and our little tutorial-cube is finished. Now apply for your 'Cube GIMP Licence' from the nearest GIMP Station ;)

4. Finished Work

Now you have a cool image of a Light-Source-Shaded Cube. You can choose <Image> Image ->

Flatten Image to merge the layers togerher so you can save as jpeg or any other format than

xcf. Or, better still, from the layers dialog, make the background invisible and choose <Image>

Image -> Merge Visible Layers so you will have the background on a separate layer and you

can work further on it if you like.

The next thing is to start using the geometrical shapes as building blocks to make things. And you can twist the beziers to make a bit more fancy stuff...

I have provided the xcf-file for the image we just created, if you want to experiment with it, although you should be perfectly able to do just as good yourself.

Thanks for your interest. tigert

It was updated for GIMP 2.0 by Raphaël Quinet.

ANTI-ALIASED THRESHOLD TUTORIAL

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Intention

The threshold plug-in works by dividing the image into two parts, dark and light, producing a 2 color image. This is often not the desired result, for some images anti-aliasing is needed, but the threshold plug-in cannot provide that. With a little utilization of the curves plug-in, we get nice results.

Problems with the threshold

On the left you we see the original image that is about to be thresholded, and on the right side we see the result. The default settings for the Threshold plug-in were used (<Image>

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First duplicate the image layer by going to the layers dialog, making sure the image layer is selected, and clicking the duplicate button (fourth from the left). We can use the original layer for some color tricks later. Now the next thing is to desaturate the image (<Image> Layers ->

Colors -> Desaturate). This way the colors will not interfere with the fake thresholding. When

the layer is grayscale, select the curves editor (<Image> Layers -> Colors -> Curves). Now we can play with the Value "channel". The image on the left displays the settings used for the example image. The space between the two dots determines how much aa the resulting image will have. The wider the gap, the more grayscale values it will have, and vice versa. The resulting image can be seen on the right.

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A neat addition

If you now take the original image layer, move it over the new one (make sure it has an alpha channel), and change its mode to "Color" in the layers dialog, you get nice results displayed above.

FILM GRAIN TUTORIAL

Intention

Real-world images have lots of noise: film grain, scanner lines, CCD noise, paper texture, and just about anything else you can imagine. Computer-generated images, on the other hand, tend to be too real. If you need to make computer-generated images look like real-world ones, then this tutorial is for you.

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Perhaps you've rendered a gorgeous 3D scene, but want to make it look more like a photograph. Perhaps you're compositing two different photos, and need make the grain match. Or maybe you're just perverse.

Extracting the Film Grain

This is a subject for another, longer tutorial. But here are the basic steps:

1. Take a noisy image.

2. Duplicate it into a new layer. 3. Blur it to remove the noise.

4. Set the blurred layer to Grain Extract mode to extract the noise. 5. Flatten the image.

6. Choose an interesting area of the noise, and make it into a tileable pattern.

(GIMP pattern file)

Some good ways of making tileable patterns include Make Seamless, the Resynthesizer and Homogenizer, mirroring, and hand-editing. You'll have to experiment a bit. In the following example, we'll use a weird, vertically-striped noise pattern. It looks like some kind of scanner noise, or perhaps an artifact of old newsprint.

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First, desaturate the image. You can do this using <Image> Image -> Colors -> Desaturate or the Desaturate filter provided with the MathMap plugin.(The latter actually returns the luminosity of an image, not a desaturated version. Technically, it's better, but it's unnecessary for most images.)

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Next add a new layer to the image, and use the bucket to fill it with your tileable noise.

Step 3

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Step 4

So far, so good. But the noise is too strong in the shadows and highlights of the image. To demphasize it, we can use a layer mask.

First, add a layer mask to the noise layer. Then, make a copy of the image, gaussian blur it with a radius of 15 pixels, and paste the blurred image into the layer mask. Use <Image> Image ->

Colors -> Invert to swap bright for dark. This will cause the grain to show through strongly in

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Next, use <Image> Image -> Colors -> Curves to adjust the value of the layer mask. We want to make the midtones bright, and the shadows and hightlights dark. You can adjust the curves to taste. Curves Dialog This increases the grain in the midtones, and reduces it elsewhere. Here's the Layers, Channels & Paths dialog for the finished image.

Related Techniques

You can use various brushes in the mask layer to selectively edit the grain. You can also use the bucket tool in Pattern Fill, Grain Merge mode to fill a selection with grain directly. Many kinds of noise can be created using <Image> Filters -> Noise -> Scatter HSV. You can apply this directly to an image, or to a film grain pattern.

To denoise an image, try <Image> Filters -> Blur -> Selective Guassian Blur. It's slow, but very nifty.

CHANGING BACKGROUND COLOR 1

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Intention

to

This tutorial shows you how you can effeciently replace the background of an image with another in GIMP, through the use of the color to alpha plug-in. The aim is to show the advantages of using the color to alpha plug-in over selection-based techniques. To illustrate this, this tutorial will use the above images as source and destination. This tutorial doesn't address the complexities of handling real-world photos in this manner, but does briefly discuss it at the end.

Why Not a Selection

The common approach to doing many things in GIMP is to first get a good selection. However, when removing an anti-aliased object from its background is not a good idea, as shown above.

You'll note that each of the three zoomed in selections above have varying amounts of the green-blue mix selected. When these are filled, we are left with flat black and slightly blueish-green pixels between them, or no transition to black at all.

Compare each with the target image below. The left one has a blue border around it. This looks somewhat neat, but not what we're going for. The middle one is close, but there are some ugly visble pixels still. You can try getting rid of all the ugly pixels, but then you'll end up with something jagged like on the right.

You can spend hours trying to find something that will work perfectly, but you won't.

Anything short of the rightmost image has some blue in the pixel, which will stick out. You can go too far, and blend it back to something close, but this is time consuming. Instead, may I suggest the rest of the tutorial?

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The first step is to activate the color to alpha plug-in. Its menu location is <image> Filters ->

Colors -> Color To Alpha, where <image> means to right click on the image. If its grayed-out, it

means that you have an indexed image. If its not there, upgrade your gimp to 1.2.x.

Step 2

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Next use the Color Picker Tool to select the background color.

Step 3

When you used the color picker to select the background, a window with the color popped up. Click, hold, and drag from the color portion of this window to the color portion of the Color To Alpha plug-in. If using Gimp for Windows, you'll have to right-click on the destination button and select the Foreground - drag n' drop doesn't work. Click OK after the color indicator on the Color To Alpha plug-in is changed to blue.

Step 4

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Step 5

Now create a New Layer (have Forground set to Red when you do this). Lower the newly created layer.

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The image should now be green on red, with no trace of blue!

This may not work as well for you for 2 reasons:

Photo's don't tend to have one color you can choose like that

The foreground may contain portions of that color that are removed by the plug-in The work arounds, respectively, are:

Apply multiple times, or just once and touch-up by hand

Paint underneath the new image with the original color to bring it back to those portions that need it

CHANGING BACKGROUND COLOR 2

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Many times you have an image with a colored background, like the one above and you want to take out the background to use the image's subject in a composition. With gimp there are many ways to achieve this, one of which is using a plug-in specifically designed for this: Changing Background Color 1.

Step 1

In this tutorial I explore the select by color option to remove a particular color from the image. The first step, after you have loaded the image of course, is to click on the Select By Color tool.

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Like other selection tools, this one provides several options that can be modified. The top row of buttons sets the Selection Mode. We will use the add option, which means any color we click on will be added to the selection. You can also use the Shift key to acheive the same result.

The other interesting setting is the Threshold. When you click on a color, the higher this setting is, the more similar colors to the one you clicked on will be selected. You can start by using the default setting and increasing it if you need to add more colors faster, or decrease it if you're selecting more then you want.

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Now it's time to start selecting the color you want to remove. Just start clicking on the color you don't want and watch the selection update. If that didn't select all the color you want, continue clicking on the unselected parts until you get the desired result.

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Finally, there is one last step before you can remove the background. You have to add an alpha channel (a common term for transparency in images) to your image. To do that you have to use the right button on the mouse to get the image menu and go to layers and add alpha channel.

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With the selection complete and with an alpha channel just choose from the image menu

<Image> Edit -> Clear, and the image background will be gone.

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After the last step you should get something like this in Gimp.

You can now use this image in a composition or in a web page with a different background like below:

Final

Of course you still have to take care of the details if you want to merge an image perfectly into another.

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COLORING A BW SKETCH

Intention

First of all you have to acquire through a scanner or something similar your sketch. It doesn't necessitate to be truly a black and white image (2 colors), often a well contrasted grayscale image is better (use contrast autosketch or/and the brightness-contrast tools).

Step 1

Create a new image of the wanted size and place below the sketch layer a pure white

background layer. Now turn the mode for the sketch layer into multiply. From now the sketch layer will stay forever over the others.

Step 2

Now let's start playing with colours!

Create a new layer and call it "Details". In this example I've used it for painting the blue doughnut. As you can see, thanks to the multiply mode, the black lines of the sketch are kept while the white zones are "transparent". Don't be too afraid of going outside the shapes, in the next steps we will see that some stuff will "disappear", covered by other layers.

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Step 3

Create a "Skin" layer over the "Details" one. Here I've coloured the skin and the shoes with the paint tool and the airbrush. For first you should fill with the base colour the shapes (use a paint tool), then apply (with the airbrush) darker shades on the edges and brighter ones over the cheeks.

Step 4

The "Details#2" layer is used for some extra details like the white text over the blue doughnut. I've used it because I want be able to change and retouch the doughnut shading without the white text (that should stay as brighter as possible).

Step 5

The "Hairs" layer contains ... well, what do you think will contain a layer called "Hairs"? Yeah, right answer! ;P Please notice only that this layer is below the sketch one but over the others, so the extra painted zones of the "Skin" layer are covered by this one. I.e. you can add some shadows over the forehead by painting over these zones.

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Finally I've added a "Shadows" layer for making the doughnut and the other elements less flat. This is the end. Still reading here? Now it's your turn! Quickly open GIMP and start playing! ;)

3-D FLOATING LOGO

Intention

This tutorial is aimed squarely at the novice GIMP user. The more experienced user may find some techniques here useful. This is the same procedure I used to create the logo on my homepage, albeit with slightly different settings. I'll point out the differences as I go along. I've taken a lot of screen shots to support this tutorial, so enjoy :)

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Fire up GIMP and create a new image. I used a white background at 500px by 200px. I feel this size it adequate as my website at the time of writing uses 500px tables.

Step 2

Start by laying down some text that is wider than 400px and not too thin. I've used a font called Pricedown. The text should be created as a new layer. If you use GIMP FreeType then it is done for you, otherwise click the New Layer button in the Layers, Channels, & Paths dialog (looks like a blank piece of paper). It will help to change the layer size to that of the image. Do so by accessing the Layers menu (right click or Control+Click on the layer you wish to operate on) and select Layer to Imagesize.

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Duplicate the text layer (text) twice. One for the highlight effect (highlight) and one for the shaded part of the effect (lowlight). The highlight layer needs to be white, so select that layer, check the Keep Trans. box on the Layers, Channels, & Paths dialog, and fill it with white. You can do this easily by dragging the white color swatch from the toolbox over to the image (assuming that the highlight layer is currently selected). Keep Trans. means "Keep

Transparency"; this will ensure that any transformations or fills made to that layer will only affect the non-transparent part of the image.

Step 4

Duplicate the text layer again and move it to the top of the Layers stack (use the little up facing arrow head on the Layers, Channels, & Paths dialog). Make sure that Keep Trans. is

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un-checked and then blur it. I used Gaussian Blur (RLE) at 10 pixels. When I did the original logo, it was set lower than this to make the effect less rounded.

You will need to make sure that the layer boundary is larger than the layer so that the blur can spread nicely. Step 2 mentions this.

Step 5

Duplicate the blurred layer once (tmp1 and tmp2). These layers are used to create the edge lighting for the text.

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Nudge one of the blurred layers (tmp1) down and to the right about 5 pixels. The precise number of pixels depends on how blurred and thus how round the text will appear to be, so use your best judgement. You can nudge layers my using the Move tool and the cursor keys on your keyboard. It doesn't matter which of the blurred layers you use in this step, as long as you know which one you didn't move \x{2013} you'll be needing to do a very similar thing to that one soon.

Step 7

Now create a selection using the blurred layer (the one you moved in step 6) using Alpha to Selection. This selection is a precise selection based on the layer and includes alpha

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other blurred layer). This was done to make sure I could see how far I moved this layer during step 6.

Step 8

Now that the layer is selected...

Step 9

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Step 10

Cut (edit/cut or CTRL+X on PC or Command+X on Mac). This will remove the blurred layers selection from the highlight layer. You could do this with channel masks, but I'm a man of simple needs and wants. There's another step after this that I haven't documented, but that's because it's the same thing again (steps 6-10) but with the other layer (tmp2: see steps 5 and 6). Move (nudge) that layer in the opposite direction (up and to the left about 5 pixels), then make the cut from the lowlight layer. Once you're done, delete the two blurred layers (tmp1 and tmp2).

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I like to take quasi-breaks while doing some images, and this is one of those times. A good time to roll a cigarette or grab a cup coffee. I also tend to clean up temporary layers occasionally.

Step 12

Now we'll add the first elements of 3D-ness to the logo. The original text layer is the base layer for any color you want to add. I'll use grey70, but you could just as easily use any old color you like. It's a good idea to play with this as you can get some funky plastic logos too. Make sure Keep Trans. is checked when you fill the layer.

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As you can see, it's starting to look like something now.

Step 14

Click the blank piece of paper on the Layers, Channels, & Paths dialog and make a new transparent layer called outline. Move this new layer down the layers stack until it's underneath the original text layer.

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Select the original text layer (the one you added some color to) and do the Alpha to Selection trick again. Right click on the image and use <Image> Select -> Grow. This will make the new selection larger by a number of pixels - I used a value of 2 pixels. Once you have a selection, be sure to reselect the new layer (outline) so that you can fill it (step 17). And below is what it looks like.

Step 16

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Fill the layer with black and deselect (CTRL+SHIFT+A on PC or Command+SHIFT+A on Mac). As you can see, the image now has more background contrast. Now, duplicate that layer and lower the copy below the original outline layer. Make sure that Keep Trans. is not checked, and blur it. I like soft shadows, so I used a Gaussian Blur (RLE) of about 30 pixels. Drop the Opacity of the layer down to about 50 and nudge it to the right and down until it looks okay.

A nice way to fill selection areas or layers that have Keep Trans. selected, is to simply drag the color from the toolbox color swatch to the layer.

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This is what the Layers, Channels, & Paths dialog should look like.

Step 19

I've duplicated the highlight and lowlight layers and made them all blend with the lower layers using the Overlay mode. This helps to make the edges more 3D.

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Step 21

Rust isn't uniform and I've decided to only worry about the lower half of the letters. Use the bezier tool on the new rust layer to start a selection that looks like...

Step 22

This. Click inside the bezier path once you close it (close it by clicking one the first node). This will create a selection. Use <Image> Select -> Feather to feather (blur) the selection. I used a value of about 10 pixels.

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Pick a nice bright orange or brown color for the rust. My site logo used a reddy-borwn color, but here I've chosen a bright orange. Fill the selection with it. Using the famed Alpha to Selection move, get the selection for the original text layer. Once you have that selection area, click the rust layer to make it active. Invert the selection (CTRL+I or Command+I) and Cut. This will leave only the part of the rust layer that actually covers the letters and not the extra.

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Change the Layer Mode of the rust layer to Muliply (Burn).

Step 25

The image should now look a little like this. Don't worry, it'll look better soon.