Scaling animation effect with the GIMP
Here is a animation to demonstrate the effects of scaling based on Alice in Wonderland, based on the GIMP version 2.8. Having drunk the magic potion Alice begins to shrink. Instead of Alice its more fun if you shrink yourself. All you need is a digital camera with a timer, a tripod and a basic knowledge of the GIMP. If you don't have a timer on your camera, or a tripod, then you'll need a friend to take a couple of pictures for you.
step 1 First take a picture of the background (fig 1) you are going to use; without you in it! Then without moving the camera take a second picture (fig 2), this time include yourself in the picture. When you are done, download the images from your camera to a computer. I'm assuming you know how to do that.
fig 1 - table and chairs
fig 2 - Table and Alice
step 2 Now the fun part. Starting with the second image (fig 2) Load this into the GIMP. You now need to cut yourself out of the picture using the scissors select tool (fig 2a). Carefully select points round your outline until you get back to your starting point. Each time you left-click with the mouse, you create a new control point, which is connected to the last control point by a curve that tries to follow edges in the image. To finish, click on the first point (the cursor changes to indicate when you are in the right spot). You can adjust the curve by dragging the control nodes, or by clicking to create new control nodes. When you are satisfied, click anywhere inside the selected area to convert it into a selection. This is denoted by the marching ants around the border. Fig 3 shows the anchor points and the different cursor symbols, e.g. when adding a control point (+), when closing the selection i.e. over the start point (two overlapping circles), when outside a closed selection (no entry) and inside the selected area (open circle).
fig 2a - Gimp toolbox - Scissors
step 3 From the edit menu select copy visible and then paste as -> new image. Now export this new image to save it with the other two images. (fig 3)
fig 3 - Alice cut out
step 4 From the file menu, select close all, making sure you have saved the new image.
step 5 Load the original background image (fig 1) into the GIMP, then drag the new image (fig 3 - Alice) on top of the background. You will need to move the image to roughly the same position you stood when the photo was taken. You should now see the combined image consists of two layers.
step 6 Next duplicate the layer containing Alice, and under the layer menu select scale layer and choose a suitable scaling factor. Repeat this step until the image has been shrunk to its final size. I'll leave you to experiment with the increment, and number of times you repeat the scaling. You now see the bottom layer (fig 1) and multiple layers with copies of Alice. (the onion skin effect).
step 7 Now you need to duplicate the background image placing each duplicate above each Alice layer, so the layers alternate between background and Alice. Leave the topmost layer as the final scaled version of Alice.
step 8 Finally starting at the topmost (Alice) layer) from the layer menu select merge down, to merge Alice with the background. Repeat this step until each Alice has been merged with the background layer below. Save the resulting .xcf file.
At this point you may want to test your animation, using the default timings. Under the filters menu select animation -> playback, to see the resulting animation.
step 9 Before exporting the .xcf file as a .gif (animation) image you may want to adjust the timings. In fig 4 you can see I have use 200ms for each frame except the first and last. These I have set to 2000ms (or 2 seconds), to pause the animation between each loop. To add the timing simply click on the frame name and add the desired timings, e.g. frame 2 (200ms) (replace). The resulting effect is shown below in fig 5.
fig 4 - Animation frame timing.
fig 5 - Alice in Wonderland
This is a very simple animation to show what is possible. The camera keeps a fixed viewpoint while Alice shrinks. Of course, an alternative approach would be to have the camera viewpoint change, to view the world from the perspective of a tiny Alice. How might this be achieved?
Another option would be to scale Alice in just one direction, by unlinking the width and height. For example, you could extend this animation by scaling Alice up again to her original height, but keeping her width the same; so she is pencil thin! The possibilities with animation are endless, and are only limited by your imagination. Many films, not just cartoons rely on animation special effects, to do things not possible, or to dangerous to do in real life.