Picket fence animation (sometimes also called barrier-grid animation) is an optical illusion. The illusion consist of two sheets – a white sheet with an image printed on it and a transparent plastic sheet with a number of black bars on it. The white sheet of paper underneath has a number of alternative images printed on it, in the form of very thin vertical stripes. In front of the picture card is a piece of clear plastic, which has vertical black and opaque stripes printed on it with thin gaps. When the plastic sheet is moved from side to side, the image printed on the sheet underneath appears to animate. A video demonstration is shown below.
You can create your own picket-fence animation at home using an open source, cross platform software Animbar.
First you will need to create the frames that make up the animation. Draw them if you can, or if you are like me, find a suitable GIF animation. Black and white silhouette type images work best, like the one below.
Now go to GIFexplode (assuming you have a GIF image that you want to convert into an animation) and convert the animation into individual frames. You can also a GIF editor like Adobe ImageReady. Save all the frames of the GIF to your computer and load them into Animbar. You may rearrange the order of images by moving them around (drag and drop). You may also remove selected images by pressing the delete key or add further images through the file open dialog. Lesser number of images (less than 10) usually produces the best results.
Once you are done with setting up the input images, compute the animation from the edit menu. You will be asked to specify a strip size – the width of the scan lines. Experiment with the width size until you get a smooth animation. I have found that smaller width (1px - 2px) produces better results. Yours may vary.
Finally save both the base image and the bar mask.
Now print the base image on a regular paper and the bar mask on a clear transparent sheet, which can buy in any stationary store. Your animation is ready.
Advice from the creator: You will obtain best results when you print the images without any scaling, anti-aliasing, dithering etc involved. Downscaling the images, thus reducing the number of pixels being printed, will decline the quality of the animation. Upscaling should be fine though.