Last week at our Digital Art Club meeting, I mentioned that I had started making a few animated gifs using Processing. Like this one.
(I’m not sure exactly why the circles look like they have such jagged edges — must have to do with the say WordPress uploads the gif. But it was my first animated gif, so I thought I’d include it anyway.)
And, of course, my students wanted to learn how to make them. A natural question. So I thought I’d devote today’s post to showing you how to create a rather simple animated gif.
Certainly not very exciting, but I wanted to use an example where I can include all the code and explain how it works. For some truly amazing animated gifs, visit David Whyte’s Bees & Bombs page, or my friend Roger Antonsen’s Art page.
Here is the code that produces the moving circles.
I’ll assume you’ve done some work with Processing, so you understand the setup and draw functions, you know that background(0, 0, 0) sets the background color to black, etc.
The idea behind an animated gif which seems to be a continuous loop is to create a sequence of frames whose last frame is essentially the same as the first. That way, when the gif keeps repeating, it will seem as though the image is continually moving.
One way to do this is with the “mod” function — in other words, using modular arithmetic. Recall that taking 25 mod 4 means asking “What is the remainder after dividing 25 by 4?” So if you take a sequence of numbers, such as
1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 11, 12, 13, 14, …
and take that sequence mod 4, you end up with
1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, ….
Do you see it already? Since my screen is 600 pixels wide, I take the x-coordinate of the centers of the circles mod 600 (that’s what the “% 600” means in Python). This makes the image wrap around horizontally — once you hit 600, you’re actually back at 0 again. In other words, once you go off the right edge of the screen, you re-enter the screen on the left.
That’s the easy part…. The geometry is a little trickier. The line
x = (75 + 150 * i + 2 * frameCount) % 600
requires a little more explanation.
First, I wanted the circles to be 100 pixels in diameter. This makes a total of 400 pixels for the width of the circles. Now since I wanted the image to wrap around, I needed 50 pixels between each circle. To begin with a centered image, that means I needed margins which are just 25 pixels. Think about it — since the image is wrapping around, I have to add the 25-pixel margin on the right to the 25-pixel margin on the left to get 50 pixels between the right and left circles.
So the center of the left circles are 75 pixels in from the left edge — 25 pixels for the margin plus 50 pixels for the radius. Since the circles are 100 pixels in diameter and there are 50 pixels between them, there are 150 pixels between the centers of the circles. That’s the “150 * i.” Recall that in for loops, the counters begin at 0, so the first circle has a center just 75 pixels in from the left.
Now here’s where the timing comes in. I chose 300 frames so that by showing approximately 30 frames per second (many standard frame-per-second rates are near 30 fps) the gif would cycle in about 10 seconds. But cycling means moving 600 pixels in the x direction — so the “2 * frameCount” will actually give me a movement of 600 pixels to the right after 300 frames. You’ve got to carefully calculate so your gif moves at just the speed you want it to.
To make displaying the colors easier, I put the R, G, and B values in lists. Of course there are many other ways to do this — using a series of if/else statements, etc.
One last comment: according to my online research, .png files are better for making animated gifs, while .tif files (as I’ve also used in many previous posts) are better for making movies. But .png files take longer to save, which is why your gif will look like it’s moving slowly when you use saveFrame, but will actually move faster once you make your gif.
So now we have our frames! What’s next? A few of my students mentioned using Giphy to make animated gifs, but I use GIMP. It is open source, and can be downloaded for free here. I’m a big fan of open source software, and I like that I can create gifs locally on my machine.
Once you’ve got GIMP open, select “Open as Layers…” from the File menu. Then go to the folder with all your frames, select them all (using Ctrl-A or Cmd-A or whatever does the trick on your computer), and then click “Open.” It may take a few minutes to open all the images, depending on how many you have.
Now all that’s left to do is export as an animated gif! In the File menu, select “Export As…”, and make sure your filename ends in “.gif”. Then click “Export.” A dialog box should open up — be sure that the “As animation” and “Loop forever” boxes are checked so your animated gif actually cycles. The only choice to make now is the delay between frames. I chose 30 milliseconds, so my gif cycled in about 10 seconds. Then click “Export.” Exporting will also take a few seconds as well — again, depending on how many frames you have.
Unfortunately, I don’t think there’s a once-size-fits-all answer here. The delay you choose depends on how big your gif actually is — the width of your screen in Processing — since that will determine how many frames you need to avoid the gif looking too “jerky.” The smaller the time interval between frames, the more frames you’ll need, the more space those frames will take up, and the longer you’ll need to upload your images in Gimp and export them to an animated gif. Trade-offs.
So that’s all there is to it! Not too complicated, though it did take a bit longer for me the first time. But now you can benefit from my experience. I’d love to see any animated gifs you make!