Luxor provides some functions to help you create animations—at least, it provides some assistance in creating lots of individual frames that can later be stitched together to form a moving animation, such as a GIF or MP4.
There are four steps to creating an animation.
Movie to create a Movie object which determines the title and dimensions.
2 Define some functions that draw the graphics for specific frames.
3 Define one or more Scenes that call these functions for specific frames.
4 Call the
animate(movie::Movie, scenes) function, passing in the scenes. This creates all the frames and saves them in a temporary directory. Optionally, you can ask for
ffmpeg (if it's installed) to make an animated GIF for you.
demo = Movie(400, 400, "test") function backdrop(scene, framenumber) background("black") end function frame(scene, framenumber) sethue(Colors.HSV(framenumber, 1, 1)) eased_n = scene.easingfunction(framenumber, 0, 1, scene.framerange.stop) circle(polar(100, -π/2 - (eased_n * 2π)), 80, :fill) text(string("frame $framenumber of $(scene.framerange.stop)"), Point(O.x, O.y-190), halign=:center) text(scene.opts, boxbottomcenter(BoundingBox()), halign=:center, valign=:bottom) end animate(demo, [ Scene(demo, backdrop, 0:359), Scene(demo, frame, 0:359, easingfunction=easeinoutcubic, optarg="made with Julia") ], creategif=true)
In this example, the movie uses two scenes, each specifying a function to draw frames from 0 to 359. For each frame numbered 0 to 359, the graphics are drawn by both the
frame functions, in that order. A drawing is automatically created (in PNG format) and centered (
origin) so you can start drawing immediately. The
finish function is automatically called when all the drawing functions in the scenes have completed, and the process starts afresh for the next frame. The second scene, calling the
frame function, shows how you can pass optional information to the function.
For best results, you'll have to learn how to use something like
ffmpeg, with its hundreds of options, which include codec selection, framerate adjustment and color palette tweaking. The
creategif option for the
animate function makes an attempt at running
ffmpeg and assumes that it's already installed. Inside
animate, the first pass creates a GIF color palette, the second builds the file:
run(`ffmpeg -f image2 -i $(tempdirectory)/%10d.png -vf palettegen -y $(seq.stitle)-palette.png`) run(`ffmpeg -framerate 30 -f image2 -i $(tempdirectory)/%10d.png -i $(seq.stitle)-palette.png -lavfi paletteuse -y /tmp/$(seq.stitle).gif`)
Many movie editing programs, such as Final Cut Pro, will also let you import sequences of still images into a movie timeline.
If you want to pass information to the frame function, such as an array of values, try these:
function frame(scene, framenumber, datapoints) ... end somedata = Datapoints[...] animate(demo, [ Scene(demo, (s, f) -> frame(s, f, somedata), 0:100, optarg=somedata) ], creategif=true, pathname="...")
Transitions for animations often use non-constant and non-linear motions, and these are usually provided by easing functions. Luxor defines some of the basic easing functions and they're listed in the (unexported) array
Luxor.easingfunctions. Each scene can have one easing function.
|List of easing functions|
Most easing functions have names constructed like this:
and there's an
easingflat linear transition.
function draweasingfunction(f, pos, w, h) @layer begin translate(pos) setline(0.5) sethue("black") box(O, w, h, :stroke) sethue("purple") for i in 0:0.005:1.0 circle(Point(-w/2, h/2) + Point(w * i, -f(i, 0, h, 1)), 1, :fill) end sethue("black") text(replace(string(f), "Luxor." => ""), Point(0, h/2 - 20), halign=:center) end end t = Tiler(650, 650, 5, 5) margin=5 fontsize(10) fontface("JuliaMono-Regular") for (pos, n) in t n > length(Luxor.easingfunctions) && continue draweasingfunction(Luxor.easingfunctions[n], pos, t.tilewidth-margin, t.tileheight-margin) end
In these graphs, the horizontal axis is time (between 0 and 1), and the vertical axis is the parameter value (between 0 and 1).
One way to use an easing function in a frame-making function is like this:
function moveobject(scene, framenumber) background("white") ... easedframenumber = scene.easingfunction(framenumber, 0, 1, scene.framerange.stop) ...
This takes the current frame number, compares it with the end frame number of the scene, then adjusts it.
In the next example, the purple dot has sinusoidal easing motion, the green has cubic, and the red has quintic. They all traverse the drawing in the same time, but have different accelerations and decelerations.
fastandfurious = Movie(400, 100, "easingtests") backdrop(scene, framenumber) = background("black") function frame1(scene, framenumber) sethue("purple") eased_n = scene.easingfunction(framenumber, 0, 1, scene.framerange.stop) circle(Point(-180 + (360 * eased_n), -20), 10, :fill) end function frame2(scene, framenumber) sethue("green") eased_n = scene.easingfunction(framenumber, 0, 1, scene.framerange.stop) circle(Point(-180 + (360 * eased_n), 0), 10, :fill) end function frame3(scene, framenumber) sethue("red") eased_n = scene.easingfunction(framenumber, 0, 1, scene.framerange.stop) circle(Point(-180 + (360 * eased_n), 20), 10, :fill) end animate(fastandfurious, [ Scene(fastandfurious, backdrop, 0:200), Scene(fastandfurious, frame1, 0:200, easingfunction=easeinsine), Scene(fastandfurious, frame2, 0:200, easingfunction=easeinoutcubic), Scene(fastandfurious, frame3, 0:200, easingfunction=easeinoutquint) ], creategif=true)
Here's the definition of one of the easing functions:
function easeoutquad(t, b, c, d) t /= d return -c * t * (t - 2) + b end
tis the current time (framenumber) of the transition
bis the beginning value of the property
cis the change between the beginning and destination value of the property
dis the total length of the transition
easeinoutbezier function accepts two additional arguments, two normalized control points of a normalized Bezier curve from Point(0, 0) to Point(1, 1). You can use these to define the shape of a custom easing transition. The Bezier curve's
y coordinate determines the acceleration. [?]