Descriptions of the different animation filters and functions available as well as a description of GIF animation.

Animation Filters In The Filters Menu

Animation Playback

Animation Playback will display your layers or GIF animation as if it were a piece of film. If the layers don't contain specific animation information, each layer will be run in Combine mode. You can also step through each frame.

This plug-in can also show you a preview of what an image will look like in a web page. You can grab the image in the playback frame, drag it out of the frame and drop the image on another window (including a browser window). Just click on the image and drag it to where you want it to go.

Note that the image doesn't need to be layered (i.e., a playable image) in order to use this function. You can use it on any ordinary JPEG, GIF or TIFF image.

Animation Optimize

A GIF animation is built of many layers. Some of the layers will probably repeat much of the information in the previous layer (the previous frame in your animation). Wouldn't it be great if you could skip all that unnecessary information? This would be difficult and time-consuming to do by hand, but there is a filter that can do it for you.

Open your animation file and apply right-click|Filters|Animation|Animation Optimize. Now look at your layers. The layers will be much smaller, because only additional or diverging information is displayed. This filter will make GIF animations much smaller and faster to download. You can also use this filter on large, multi-layered XCF files to reduce their size.

Animation Unoptimize

After you have optimized an image (using Animation Optimize or by hand), it is usually quite hard to scale and your manipulations will often produce an ugly result. The Animation Unoptimize filter solves this problem, so use this filter before you make any alterations to an optimized image.

Filter All Layers

Filter All Layers is used to create animations with the GAP plug-in (see "Advanced Animation With Gimp Or How To Use AnimFrames" starting on page 639), but you can apply it to any kind of multi-layered image. When you select this filter, a browser will appear. The browser is much like the DB Browser, except that only plug-ins are listed.

Select the filter that you want to apply, and specify how you want to apply it, by selecting constant or variable. When you have made your choice, a filter dialog will pop up asking for values. If you chose constant, the dialog will appear only once, and the values you specify will apply to all layers. If you chose variable, the dialog will appear for every layer so you can apply different values to each layer.

How To Create A GIF Animation

Gimp is a great tool for creating GIF animations. Gimp treats each layer as a frame. The Background layer is Frame 1 and each new layer is a new frame. When you add a new layer to the background layer, name it Frame 2, Frame 3 and so on.

Specifying The Delay Of Each Frame

Edit the layer name by double-clicking on a layer in the Layers & Channels dialog. Rename it Frame X (xxxxms), where X is the frame number and xxxx is the delay in milliseconds. Naming a frame Frame 5 (100ms) will give that frame a delay of 100 ms.

Combining Frames

To make a layer combine with the previous layer (combine means that Frame 2 will be added to Frame 1 (the background), Frame 3 will be added to Frame 2 and Frame 1, and so on), name the layer Frame X (xxxxms) (combine).

Replacing Frames

To make the animation work like a real movie (i.e., each new frame replaces the former), add (replace) instead of (combine). You can (combine) and (replace) in any order.

Note that when you save your GIF, you'll see a dialog box that asks you about Default disposal where unspecified. Don't check Don't care because that will make the layers combine without showing up in the Gimp layer dialog as (combine). Just choose combine, and the settings in the layer dialog will still be preserved.

An example of five layers/frames:

· Background (100ms) (replace)

· Frame 2 (100ms) (combine)

· Frame 3 (100ms) (replace)

· Frame 4 (100ms) (combine)

· Frame 5 (100ms) (replace)

The previous five frames will be played back in this order with a 100 ms delay between each frame:

· Background

· Frame 2 + Background

· Frame 3

· Frame 4 + Frame 3

· Frame 5

· Background

and so on until you stop it.

Note: Combine combines the frame with the previous frame, but if you have set the background layer to combine, it will not combine with the top layer. The background layer will always replace the top layer when the loop starts over again.