(First published at Wilber's Wiki)
This tutorial was last tested for the Gimp '' 2.2.12 ''
This tutorial first explains how GIF animations are treated by the Gimp and then expands on that foundation by explaining how the Gimp Animation Package takes Gimp animation to the next level. It will explain how to install the GAP from the Redhat package--even for non-Redhat systems, how to obtain the GAP documentation that the Redhat package apparently leaves out, and, most importantly, de-mystifies the GAP for creating GIF animations for the Web.
It will be as complete as I can make it, providing a solid foundation for understanding how the GAP treats animations and then explaining the finer points of the package to illustrate some of its more useful features for GIF animation. My goal is to provide a one-stop tutorial for Gimp animation that goes from complete beginner to intermediate knowledge that other tutorials skip or gloss over.
Simple Gimp Animations
GIF animations are sequences of grayscale or indexed color images with timing information attached. The Gimp allows the creation of animated GIFs by placing each frame of an animation in its own layer and attaching timing information through modification of the layer comment.
The Gimp provides some script-fu add-ons that create animations that may be integrated with more complex GAP animations as well as a way to play animations either created by or loaded into the Gimp. These add-ons are found in the Script-Fu/Animators menu in Gimp 2.2 and in the Filters/Animation menu in Gimp 2.4. For those unfamiliar with the preceding menu path, refers to the window containing your image. Script-Fu is a top-level menu in this window. And Animators is a submenu of the image window's Script-Fu menu. To play animations in the Gimp, open the Filters/Animation/Playback... item. This will open a new window containing a view of the first frame of the animation along with controls for playing the animation in a loop or for stepping through it frame-by-frame.
Another useful Gimp feature for creating GIF animations is the
To get started, create a new Gimp image by opening the
Alternatively, open an existing image by using the
This simple example will not go into a lot of detail about hand-crafting animations other than to show you the general procedure. I only want to explain it in enough detail so that if you need to, you can fine-tune an animation once it is created by one of the other automated methods I will describe. More detailed tutorials for simple GIF animations already exist at gimp.org.
Add images to your animation by copying and pasting or by duplicating the current layer and modifying the new copy. New layers can be created with the Layer/New Layer... dialog or Layer/Duplicate Layer menu item, by pressing the New Layer or Duplicate Layer buttons in the Layers dialog, or, after pasting an image into your animation, by pressing the New Layer button in the Layers dialog to turn the pasted image from a floating selection (Pasted Layer) into a new layer.
Once you have collected all of the images of your animation and pasted them as layers into your Gimp file, you can modify each layer's comment and add timing information. To do so, double-click the bottom layer in the Layers dialog, which is the first frame of the animation. This will enable you to edit the layer's comment. Timing information should be formatted as follows:
layer 1 (2000ms)
The number inside the parentheses indicates that this frame of the animation should be displayed for 2000 milliseconds, or 2 seconds. The layers can be named any way you wish, otherwise. Numbering them sequencially helps identify them, but is not strictly necessary. Press the Enter key on the keyboard when the comment is complete, then the up arrow key, and press Enter again to edit the comment for each layer in turn.
When you have finished entering timing information for all of the frames you can view the results by opening the Filters/Animation/Playback... dialog.
When you are satisfied with the results, optimize your animation with the Filters/Animation/Optimize (for GIF) menu item. This will create a copy of your animation. Save it with a .gif extension. Be sure to select the Save as Animation radio button in the following dialog. Otherwise, the Gimp will flatten the image by combining all layers into a single layer.
[*]creating a Gimp image file
[*]adding image layers
[*]modifying the layer comment by adding timing information
[*]optimizing for GIF
[*]and saving as a GIF animation
are all there is to creating animations with the Gimp. Except, of course, that there is a whole lot more to it than that if you want to create ultra-cool effects and complex transitions, which we will get into next.
Simple Gimp Animators
Now we will move on to some more interesting features of the Gimp for generating animations automatically. For this process we will be taking advantage of the Gimp's logo creation script-fu's. These scripts allow you to create and customize cool-looking text that you can animate with the Gimp's built-in animators.
Begin by opening the
For now, accept the defaults in the dialog that pops up and watch this script go to work. It will create a new image with the word ALIEN in green, glowing text on a black background. Make sure the new image's window is selected and go to the Layers dialog. Right-click on every layer and click Merge Down from the pop-up menu until only one layer remains. Then, from the new image, open Script-Fu/Animators/Rippling....
Accept the defaults in this dialog for now. Again, a new image will be created, this time with a warped version of the ALIEN text from the first image. From this second new image, select Filters/Animation/Playback.... A new window appears containing a view of the first frame of the animation. Click the Play/Stop button. The Gimp now plays back your newly-created animation. When you are done, click the Close button. You can now save the animation as a GIF using the procedure outlined above for creating simple Gimp animations or as a Gimp .xcf file for use later in other animations.
The script-fu's for logos offer the ability to change the text, font, and colors used for creating images and the animation script-fu's allow you to customize the number of frames and other parameters specific to each animator. Some require your image to have multiple layers; some only work with one. Play around with both the logo and animator script-fu's to see what kinds of cool text effects you can create and to see what other interesting animation effects you can generate.
Windows users have it easy. There is a setup program available that installs the GAP at the win-gimp website. Download the most recent version to your desktop. (Version numbers are NOT decimal the way mathematical numbers are, so version 1.2 is older than version 1.15.) It is a zip file. Open it and drag the setup program to your desktop. Then double-click on the setup program to install it. Red Hat users have it easy. There is an RPM package that does the same. Just type sudo rpm -Uvh gimp-gap-2.0.2-4.i386.rpm. Debian users have it easier still... sudo apt install gimp-gap. They don't even need to download it first. Blah, blah, blah. I use SuSE, which normally has nice packages available. Not so with the GAP. The source code for GAP is at the gimp-gap download page. If you have development files installed on your system, you may be able to compile and install it from source:
$ ./configure $ make $ su password: # make install
An alternate method for installing the GAP on an RPM-based Linux system without a development environment is to install the Red Hat package and move the installed files to where your distribution installs the Gimp, so that the next time you start it up there is a nice, new Video menu added to your image windows. The RPM package can be downloaded from rpmFind.net. It is not the most recent version of the GAP, however. After installing this package with your package manager you will find the GAP plugins at /usr/lib/gimp/2.0/plug-ins and the GAP scripts at /usr/share/gimp/2.0/scripts. To locate the system directories used for plugins and scripts by your version of the Gimp, open the
The RPM package neglects to include the documentation for the GAP. It is included in the source tarball for the GAP, though, so if you download and untar it from the gimp-gap source repository, the doc files will be there. They are quite instructive once you have a basic grasp of how the GAP works.
If everything goes smoothly, the next time you open an image in the Gimp, there will be a new menu on all of your image windows labeled Video. If not....
Introduction to the Gimp Animation Package
The Gimp Animation Package does much more than allow you to create GIF animations; full-blown videos can be edited with it. But for our purposes, the GAP's GIF animation features will do. (If you are looking for a tutorial explaing how to create avi's or mpeg's, this it not it. There are tutorials for those features, and I have links to them at the end of the tutorial. In particular, the tutorials at carol.gimp.org may be of help, and Carol can be contacted directly on the GIMP User's mailing list if you have questions about any of the material.)
As I said earlier, the GAP takes Gimp animation to a whole new level. Where the Gimp treats each layer of a multi-layer image as a frame of an animation, the GAP treats each Gimp XCF file as a multi-layered frame of a single animation. The process of editing animations with the GAP creates as many Gimp XCF files as there are frames in your target animation. And each of those frames will contain multiple layers.
If you have ever created GIF animations with the Gimp that contained fading between different graphical elements and had to merge layers over and over for each frame by hand, you will appreciate what the GAP has to offer. (I used to do that with 300-frame banners that contained quite complex transition sequences. The process took me about 10 hours to complete and I had to use a spreadsheet to keep track of my work. That is what motivated me to learn GAP.) It eliminates all of that by handling it automatically. Instead of having to calculate opacity changes yourself, you specify a starting opacity and an ending opacity and the number of frames for the transition. The GAP does the rest. It does the same for moving graphical elements from point to point in your animation and for perspective and rotation affects as well.
In order to create and edit animations with the GAP, your destination files will have to be able to handle layers and both source and destination files will have to have the same color mode, RGB or indexed. Mixing the two color modes will not work. The Gimp's native XCF format is perfect for your destination file format. Source images can be any format as long as their color mode matches that of your destination frames. The GAP is very particular about the names you use for your destination files, also. The format is any-old-filename_000001.xcf. The part of the name it is picky about is the _000001.xcf part. The other part doesn't matter. If you try to operate on a file with any other file name format, the GAP will simply display an error message and exit.
So, to get started with the GAP, create a Gimp XCF file, end its name with _000001.xcf, and store it in its own folder. If you don't put it in its own folder you will end up with as many XCF files as there are frames in your animation populating whatever directory you happen to store it in. If that is your desktop, you'll have a huge mess to clean up later. Better to corral your animation in its own folder ahead of time and avoid the cleanup job altogether.
Now that you have a correctly named Gimp XCF file you need to create some frames for the GAP to work with. Remember, frames are just Gimp XCF files that have the correct file name format. You can create copies of the initial frame yourself from the shell or use the Video/Duplicate Frames... dialog.
The bottom slider of this dialog is labeled N times, and it will duplicate your animation frame as many times as you specify. So, if you want to create a 200 frame animation, set this slider to 199. Incidentally, the slider will only increase to 99, but the spin box next to it may be used to increase the number of frames duplicated beyond 99.
When you click the OK button your frames are created in the same directory where your initial frame resides without any further interaction from you. If you look in that directory, you will see many Gimp XCF files with _000002.xcf, _000003.xcf and so on as the final part of their file names.
The next step is to create a source image. This may be an XCF file or some other file format, but it may be named anything you like. You may place it in the same directory as your animation frame files. This file may contain multiple image layers, each being a different source image. Be sure that this file and your animation frame files have the same color mode set, either RGB or indexed. Otherwise, the GAP will not recognize it as a valid source image.
This is a good place to store the logo text created with the Gimp's script-fu's. If you delete the background layers from the images created by these logo scripts, animating them against the background layers in your animation will be much easier. Also, placing them in the upper left-hand corner of the source image will make it easier to precisely position them in your animation; the GAP calculates the upper left-hand corner of your source image's source layer from the upper left-hand corner of the image canvas, not the layer's upper left corner. I find it convenient to place horizontal and vertical guides at positions 0 and 0 on the source image canvas, so that when I move my source layers into position they snap into the upper left-hand corner. I also give them meaningful names to more easily identify them in the GAP's Move Path dialog, where they are identified by their layer comment.
The Move Path Dialog
Once you have your source image created and populated with layers of graphics and text, it's time to start making things move. With one, and only one, of your animation frames open and one or more source images open, open the Video menu on the animation frame window and select Move Path.... The reason I put it that way is that having more than one animation frame open may cause corruption of your animation files. So be sure you only have one animation frame open at a time. You can have multiple source images open. Just be sure that they and your animation frames all have the same color mode, e.g. Gimp xcf files that are all either indexed or rgb, or Gimp xcf destination files that are indexed and gif source image files, which are always indexed. Also, be sure that you open the Move Path dialog from your animation frame window's Video menu, rather than from your source image's Video menu. The Move Path dialog expects the image where it was invoked to be a valid GAP frame file and will stomp its finicky feet if it isn't.
If you have followed my instructions precisely, the Move Path dialog should appear and the Source Image/Layer combo box at the top of the dialog should have one of your source layers selected.
Incidentally, there is no reason to keep your source layer on screen for any of this; you will not be referring to it from here on. It only needs to be open so that the Move Path dialog can use it. The Move Path dialog will show you everything you need to see, (well, almost everything).
The Move Path dialog initially selects the upper-most layer of your source image. If this is not the one you want to work with, select another layer from the Source Image/Layer combo box. Two other settings in this dialog will make working with your source layer possible. The first is the Instant Apply check box found near the bottom left of the dialog.
This will instantly update the preview pane of your animation, which is located just above it. This allows you to see what you are doing. The second is the Step Mode combo box located directly below the Source Image/Layer combo box.
This box is always initially set to Loop. What this means is that the GAP will loop through each layer of your source image, mapping each layer to one frame of your animation. If your source image were an animation of its own, this might be a good setting to keep, as it would allow you to integrate an existing animation file into your GAP animation. But if what you want to do is animate a single layer of your source image, then set the Step Mode combo box to None.
This combo box has several other settings available. They are Loop, Loop Reverse, Once, Once Reverse, Ping Pong, and None. As you might guess, these will loop through each layer of your source image (loop), repeatedly mapping layers to frames, do the same thing in reverse (loop reverse), map each layer only once (once), only once in reverse (once reverse), map forward and then backward repeatedly (ping pong), and none (none), which will stick with a single layer. The other options, which are the same as the ones above, but prepended with Frame are for integrating other GAP animations into the current GAP animation and work the same way as just described.
So, to animate a single layer of your source image, select None from the Step Mode combo box.
The GAP operates on your animation by calculating the changes that you specify between defined points. A point is a sequencially numbered collection of attributes that defines the state of your animation at a given point in time. By default, the first point corresponds with the first frame of your animation and the last point corresponds with the last frame. For instance, you may specify that at point 1 your source image is fully transparent and that at point two it is fully opaque. You may further specify that your source image is located at the bottom left corner at point one and at the upper right corner at point 2. This allows you to think only about the starting and ending state of your animation sequence. You don't need to think about how to get from point A to point B (or, in GAP's terms, point 1 to point 2); the GAP handles all of the details of calculating opacity changes and movement of images from one place to another. If you preview your animation at this stage, your source image will slowly come into view as it moves from the lower left corner to the upper right corner, where it will reach full opacity before the animation loops and begins again. I'll use this simple animation sequence to explain the GAP's features.
These two changes, opacity and position, are controlled by the Opacity slider and by the X and Y sliders.
Additionally, how your source image is placed depends upon what part of it is used to measure its position. This is controlled by the Handle combo box and may be any of the following values: Left Top, Left Bottom, Right Top, Right Bottom, or Center, which refer to the source image corners and center.
These handle positions are influenced by where in your source image the source layer resides. If your 50 pixel by 50 pixel source layer is at the bottom right corner of an image with a 300 pixel by 300 pixel canvas, the upper left corner will be at 0, 0 of the source image's canvas, not the source layer's upper left corner. And the center will be measured from that same corner of the canvas to the lower right corner of the canvas. Thus, to get the behavior you want from these settings, it is advisable to always place your source layers in the same position you expect to use as a handle in the Move Path dialog. For instance, if you want to use the center handle in the Move Path dialog, center the source layer in the source image. If you want to use the right bottom handle, place your layer at the lower right corner of your source image. To center a layer in your source image, make sure it is active in the layers dialog, then cut it and immediately paste it back into the source image and click the New Layer button in the layers dialog. Rename it if you want a descriptive label for the Move Path dialog's Source Image/Layer combo box.
So, to work with one layer of your source image, set the Step Mode combo box to None. To position the upper left corner of the source image at the lower left corner of your animation, check the Instant Apply check box so you can see what you are doing and move the X and Y sliders until your source image comes into view in the preview pane at your animation's lower left corner. Adjust the Opacity slider to zero to make the source layer transparent. Now you have completed the settings for the first point in your animation, which is created for you automatically by the GAP.
One thing you need to know about the preview pane of the Move Path dialog is that it does not always show you a complete view of your animation, particularly the right side and bottom edges of your animation. It sometimes appears that your source layer is beyond the right edge, when, in fact, it has not reached it yet. To move source images to the exact right edge of your animation sometimes requires knowing how many pixels wide your source layer and animation both are. Then, by using the X and Y spin boxes, you can precisely position your source layer. I usually keep a calculator close by when creating animations.
Incidentally, you can position source layers by clicking and dragging in the preview pane. If you can see how the source layer interacts with other elements of your animation at that point, this can be a convenient method of moving images. To make this easier, you can set the frame shown by the preview pane by adjusting the Frame slider at the bottom of the Move Path dialog.
This will update the preview pane by showing you the corresponding frame of your animation. Then you can drag your current source layer to visually position it in relation to existing elements of your animation. That way you don't have to work blind.
To adjust the settings for the second point you must first create one by clicking the Add Point button.
When you do, the Current Point indicator above the X and Y sliders will read  of  and your settings from point one will be copied to point two. Now, move the Opacity slider back to 100 and adjust the X and Y sliders to position your source layer at the upper right corner of your animation. You are done adjusting the values for point two and are ready to preview your animation to see how it plays.
Click the Anim Preview button at the bottom of the dialog. Another dialog pops up.
Select Exact Object on Frames and set the Scale Preview slider to 100. Then click the OK button. The GAP creates an animation file containing your settings and brings up the Gimp's Animation Playback dialog. Click Play/Stop to play the animation. Click the close button and close the file generated for the preview without saving.
At this stage you can add more points to your animation, delete the current point, delete all points, and insert points. You can navigate between points with the Next Point, Prev Point, First Point, and Last Point buttons.
If you add a third point, the time between points 1 and 2, and between points 2 and 3, will be divided equally. By default, point 2 will be half way through the animation. To change this, make point 2 the current point and adjust the Keyframe spin box located below the X and Y sliders to make point 2 occur at a particular frame of the animation. In a 100-frame animation point 2 will usually occur at frame 50. Setting it to 25 will speed up the animation from point 1 to point 2 and slow it down between point 2 and point 3.
Keyframes can only be set for points 2 through the next to last point. So, how can you key point 1 to a frame other than frame 1 and the last point to a frame other than the last one? That is set with the From Frame and To Frame sliders in the lower right corner of the dialog. This allows you to work with a subset of your animation without affecting every frame, so that you can, for instance, insert a source image midway through your video. When working with a subset of your animation frames the Anim Preview button only generates previews of the subset of frames you are working with. To see a preview of your entire animation will require generating an animation file from your frames using the /Video/Frames to image... dialog, which I will get to later. This can only be done after dismissing the Move Path dialog, unless you are working with every frame of your animation at the time. Unfortunately, the GAP only allows you to have one of its dialogs open at a time. This is really a limitation of the Gimp, rather than GAP. The GAP is really a set of plugins. Each dialog is a separate plugin, and the Gimp only allows one plugin to be active at a time.
Now, let's suppose you are happy with how the first source layer looks in your animation. You want to save the state of your animation by clicking the OK button in the Move Path dialog. Until you are ready to save your changes, avoid this button like the plague. You cannot easily undo your changes if you accidentally click this button prematurely. It can be done, but not automatically. Clicking this button closes the dialog and commits your changes to each frame of your animation without any further interaction from you. If you are not done adding images and text to your animation and you want to add more, that's Okay. Just open the Move Path dialog again and select a different source layer from the Source Image/Layer combo box and begin again. All of the settings from your previous use of the Move Path dialog will be gone. It will be like starting over, only your previous work will be visible in the preview pane if you cycle through the existing frames.
Perspective, Layer Stack, Scaling, Rotation, Paint Mode, and Selection Handling
At this stage you may want to play with the other settings the Move Path dialog offers. The Perspective tab has 8 spin boxes, one for each source layer corner's X and Y component. It will allow you to shear or adjust the source image perspective and, of course, to animate changes in perspective.
Using Instant Apply, you can adjust these spin boxes one at a time in small increments or decrements to see the effect on your source layer's appearance. Be careful, though, about doing so with large images. It can take a lot of processing power to use this feature with Instant Apply enabled. But used together with the Opacity slider and the X and Y position sliders, interesting effects can be created.
The Layerstack slider in the lower right corner of the dialog controls how your source layer is inserted into your animation.
At 0, your source layer is placed above all other layers of your animation. Larger values place it progressively farther down in the stack of layers, behind other elements.
You can scale the source layer using the Width and Height spin boxes on the Scale and Modify tab.
By default, these spin boxes scale the source layer to 100% of its size. You can scale it smaller or larger as you wish, and you can scale it vertically and horizontally by arbitrary amounts if you click the chain link to the right, which will allow independent adjustments to each spin box.
The Rotate slider, located under the Opacity slider on the Scale and Modify tab, will rotate the source layer clockwise or counterclockwise depending on whether it is given positive or negative values, respectively.
And your image may be rotated by arbitrary amounts. Amounts are measured in degrees of rotation and may be multiples or fractions of complete circles. The rotation will occur on the Z axis. That is, your view of the rotation will be along the line of the axis. If you want the rotation to occur from front to back/back to front, there is a rotation script-fu animator available from the Gimp's plugin repository that will do that for you. Just use it to create a separate animation and integrate it with your GAP animation following the instructions I will give later in this tutorial.
The Mode combo box, located to the right of the Source Image/Layer combo box, lets you determine the blending mode used for the current source layer.
See the Gimp's documentation for more information about the paint modes available here.
If you make a selection in your source image, you can use just that selection in your animation by setting Use Selection (from initial source image) or Use Selections (from all source images) from the combo box on the Selection Handling tab.
Feathering of the selection(s) is controlled by the Selection Feather Radius slider on the same tab.
To smooth out the appearance of rapidly moving images in your animation, there is a cool setting on the Advanced tab of the Move Path dialog called Tweensteps. It allows you to create a fading trail of copies of your source image that overlap each other. This creates the illusion of smooth motion in your animation. Try a setting of between 6 and 8. Too high a setting will result in massive processing and will slow down the generation of previews and of saving your animation, and there is a diminishing return of effect beyond a certain number of steps. Experiment to find a good value.
You can adjust the starting and ending opacity of the tweensteps, but the defaults seem to work well.
The Tracelayer checkbox will create a comet tail effect for objects that move. The difference between this and tweensteps is that the trail is smoother and longer lasting than the tweensteps effect.
The bluebox checkbox allows you to change the opacity of a particular color. That color is controled by the Keycolor button, which shows the currently active keycolor. Clicking this button brings up the Bluebox dialog.
Opacity, threshold, and feathering can be very finely tuned. The main controls to pay attention to are the keycolor dialog, source alpha and target alpha sliders, and the preview button, which allows you to see the effect of your choices in the other controls. By keeping the Feather Edges box checked and adjusting the feather radius you can create a kind of ghosting of images that consist of a single, solid color.
Setting the Frame Rate
When you are done adding source layers to your animation and setting points, it is time to create a real animation from your GAP frame files. The first step in this process is to open the Video Navigator dialog from your frame image's Video/VCR Navigator... menu item.
This dialog has a spin box labelled Framerate. Set this to the number of frames per second desired and close the dialog. Your setting is saved automatically.
The next step is to create an image file that contains the animation you've been working on. Open the Video/Frames to Image... dialog.
This dialog's default settings are appropriate for our purposes. Simply click OK. The gap generates an animation file and opens it.
At this stage the steps are identical to creating a simple animation. You can preview it using the Gimp's Filters/Animation/Playback... dialog and you can optimize it with the Filters/Animation/Optimize (for GIF) menu item. Save the resulting image as a GIF and select Save as Animation from the following dialog to create your animation file.
One of the nice features of the Gimp is the ability to animate still images with its script-fu animators. These scripts create simple animation files that you can incorporate into your GAP animations. To do so, use the animation file as your source image and set the Stepmode combo box to something other than None. As stated above, this combo box defaults to Loop, which will fetch one layer of your source animation and map it to one frame of your target animation and will loop repeatedly through the source image's layers until there are no more frames in your animation to apply the source image layers to. All layers of the source image will be used. In this case there is no need to select a source layer, unless you need to start animating at a particular position in the source animation. If that's the case, just select the source layer you want the animation to begin with.
But it gets even better. You can incorporate other GAP animations into the current GAP animation in the same way. Just open the first frame of the other GAP animation as your source image and set the Stepmode to Frame Loop or one of the other Frame values. These settings are designed for combining GAP animations into the current animation. If you use Frame None as the setting, you can select a single frame from the source animation and insert it in its entirety into your current animation, treating a multi-layered frame as a flat image.
The Move Path dialog has a SpeedFactor spin box located under the Source Image/Layer combo box. This controls how fast a source animation is "played back" when integrating it into a GAP animation.
This setting controls the frame rate of the source animation in relation to the target animation's frame rate. 1.0 exactly matches source and target frame rates. 0.5 maps one source frame to two target frames, i.e. plays the source at half speed. 2.0 doubles the source animation's speed in the target animation.
Animating Layer Masks
Some really cool transitions and other effects can be created using animated layer masks in GAP. The problem is getting the masks into your GAP animations and making them move. It isn't exactly straightforward, especially when you are used to quickly adding a layer mask to a single image layer in the Gimp's layer dialog.
How do you add a mask to a whole set of GAP frames? And how do you make that mask move?
The answers are somewhat irritating at first, because they seem so complicated, just like the GAP itself does when you first start using it. But the procedure is really quite simple once you understand it. Create a gray scale image to use as a mask, animate that image either separately or as part of your main animation, and then turn the layer stack containing your mask image into actual layer masks for your frames Delete the original layer stack afterwards.
Begin by making a gray scale image you want to use as a mask and animating it using the techniques I outlined above. Here is the animation mask I created.
I kept this as a GAP animation and used a stepmode setting of Frame Once in the Move Path dialog to integrate it with my animation. Place your animation mask just above or just below the layerstack you want to use your mask on. Once you finish inserting it into your animation you need to convert it into a layer mask for the layerstack it is to apply to.
To do this open the Video/Frames Modify... dialog.
Select the Copy layermask from layer above option from the function combo box and enter the layerstack number to which you want to add a layer mask in the layer pattern text box. If you want to operate on only a subset of frames, change the From Frame and To Frame sliders. But be careful in this case that you set the layerstack correctly. Once you are done click the OK button.
After the operation completes you need to delete the mask layer or turn off its visibility. You can delete it using the /Video/Frames Layer Delete... dialog.
The result of doing all of this with an animation I created using two night time skylines, one for Melbourne and the other for Las Vegas is here. Compare the animation mask above with this image.
Many, much more interesting effects can be created using animated masks in GAP. Have fun.
One limitation of the automation offered by the Gimp's animator script-fu's and of the GAP is that the timing information for all frames is usually uniform. You can tweak the settings for individual frames after creating an animation file from the frame image's Video/Frames to Image... dialog simply by editing each target image layer's comment in the Layers dialog.
You can use one of two modes for each frame of your animation, freely mixing modes from frame-to-frame--(combine) and (replace). Typed into the layer comment after the timing information exactly as shown, these modes allow your animation frame to combine with previously displayed frames or to replace them, respectively. For example, if you want to display layer 2 for 3 seconds and to completely replace layer 1, type the layer comment as follows:
layer 2 (3000ms)(replace)
(combine) is the default mode.
There are two general paths you can take to optimizing your animation. You can optimize it as an RGB image and then convert it to indexed, or you can convert it to indexed and then optimize the indexed version. I suggest you try both methods to see which results in smaller images for each project.
At this point you should be able to create nice animated logos using the GIMP's Logo script-fu's, animate them using the script-fu animators, and incorporate them into GAP animations along with other text and images. The documentation that should come with the GAP rpm's (it does come with the source code) explains all of the GAP's features in detail. I'll leave the rest up to you.
[*]Gimp Simple Animations Tutorial
[*]Gimp Using GAP Tutorial
[*]Gimp Advanced Animations Tutorial
[*]Advanced Animation Simplified
[*]Flash Effect Using GAP
[*]Sniper Scopt Effect Using GAP
[*]Toteu Advanced Animations Tutorial
[*]Advanced Animation Techniques Using GAP
[*]Fading Frames With Gimp GAP
[*]Fading Transitions With GAP
[*]Inserting Animated GIF's
[*]Flashing Text Tutorial For GAP
[*]Flash-Based GAP Tutorial (Excellent!)