burns 0.0.4

Ken Burns pan/zoom video effects: turn a still image (or a sequence of stills) into a cinematic pan/zoom film.

burns

Ken Burns pan/zoom video effects: turn a still image — or a sequence of stills — into a cinematic pan/zoom film.

The Ken Burns effect animates a static photograph by slowly panning across it and zooming in or out, giving still images a sense of motion. burns does exactly that, with a tiny API and no configuration required — and a clean, render-agnostic motion spec underneath so the same path can drive Python today and other renderers later.

pip install burns

burns needs ffmpeg available on your system (moviepy uses it to encode video). On macOS: brew install ffmpeg. On Debian/Ubuntu: sudo apt-get install ffmpeg.

Demo

Starting from a single still image:

…two lines of code turn it into two different Ken Burns films — a slow zoom-in ("push") and a lateral pan ("drift"):

from burns import ken_burns_video, ken_burns_path

ken_burns_video("demo_landscape.jpg", ken_burns_path(1, zoom=1.4, pan=0.06), duration=4.0)
ken_burns_video("demo_landscape.jpg", ken_burns_path(2, style="drift", pan=0.14), duration=4.0)

style="push" — eased zoom-in	style="drift" — lateral pan

The full script that generated this still and these GIFs is misc/generate_demo.py.

Quickstart

A standard 2-second push-in, written next to the source image:

from burns import ken_burns_video

ken_burns_video("photo.jpg")          # → photo_kenburns.mp4

That's it. The result is an mp4 that slowly zooms into the center of photo.jpg.

The motion spec: BurnsPath

The camera motion is a BurnsPath — a pure, time-parameterized spec. Its core is evaluate(t) -> Rect for t ∈ [0, 1]: where the viewport is at each instant, independent of any renderer, frame rate, or duration.

A rect is Rect(x, y, w, h) — a normalized window over the image, top-left origin, every component in [0, 1]. Rect(0, 0, 1, 1) is the whole image; a smaller w/h is zoomed in. The common cases have one-liners:

from burns import ken_burns_video, BurnsPath, Rect

# The 90% case: push from the full image toward a point at a given zoom.
ken_burns_video("photo.jpg", BurnsPath.push_in(1.3, to=(0.65, 0.40)), duration=5.0)

# The canonical two-rectangle (Start → End) case, full control:
path = BurnsPath.from_start_end(
    Rect(0, 0, 1, 1),                       # start: whole image
    Rect.from_center_zoom(0.65, 0.40, 1.2), # end: zoomed toward upper-right
    easing="ease-in-out",                   # the cinematic default
)
ken_burns_video("photo.jpg", path, duration=5.0, saveas="out.mp4")

# N keyframes for a multi-beat move (a hold = two equal keyframes):
path = BurnsPath(keyframes=[
    (0.0, Rect(0, 0, 1, 1)),
    (0.5, Rect.from_center_zoom(0.65, 0.40, 1.2)),
    (1.0, Rect.from_center_zoom(0.35, 0.60, 1.3)),
])

Easing is a CSS timing function ("linear", "ease-in-out" (default), "cubic-bezier(...)", or any callable) and is composed over the geometry — motion shape and motion speed stay orthogonal.

Output aspect ratio is independent of the source image. Set output_aspect to make a widescreen clip from a portrait photo (the renderer cover-crops, never stretches):

ken_burns_video("portrait.jpg", BurnsPath.push_in(1.4, output_aspect=16/9), duration=6.0)

Let burns design the motion for you

Hand-authoring rectangles for every image gets tedious. ken_burns_path generates a cohesive, deterministic, non-repetitive path from a little intent — pass the image's position (index) and it picks the framing. Duration is supplied at render time, so a path is reusable across clip lengths:

from burns import ken_burns_video, ken_burns_path

# index seeds the focal direction; odd indices push in, even pull out.
ken_burns_video("photo.jpg", ken_burns_path(1), duration=5.0)

# styles: "push" (zoom-led, the default) or "drift" (pure horizontal pan)
ken_burns_video("photo.jpg", ken_burns_path(2, style="drift"), duration=5.0)

# easing controls the velocity curve (default "ease-in-out"); "linear" is constant
ken_burns_video("photo.jpg", ken_burns_path(1, easing="linear"), duration=6.0)

Multi-image films

ken_burns_film renders a sequence of (image, path, duration_s) panels as one continuous film — a single encode pass, so there are no concatenation seams and no per-image freeze frames at the cuts. Pass an optional pre-built audio track to mux it in.

from burns import ken_burns_film, ken_burns_path

panels = [
    ("a.jpg", ken_burns_path(1), 4.0),
    ("b.jpg", ken_burns_path(2), 4.0),
    ("c.jpg", ken_burns_path(3), 4.0),
]
ken_burns_film(panels, saveas="film.mp4", fps=30, audio_path="narration.mp3")

Interop: one spec, many renderers

A BurnsPath serializes to a small versioned JSON document via path.to_dict() (and back via BurnsPath.from_dict(...)). That is the wire format: the same spec can be evaluated by this Python renderer, or by a JS/TS renderer / CSS preview that mirrors the trivial evaluate(t) math — no renderer owns the motion.

API

Object	What it does
Rect(x, y, w, h)	A normalized viewport over the image. .from_center_zoom, .clamped, .to_pixels, .zoom, .center.
BurnsPath	The motion spec. .evaluate(t) -> Rect, .from_start_end, .push_in, .reversed, .to_dict / .from_dict.
ken_burns_path(index, *, style="push", zoom=1.10, pan=0.03, easing="ease-in-out", output_aspect=None)	Deterministic per-index BurnsPath for a sequence.
ken_burns_video(image, path=DEFAULT_BURNS_PATH, *, duration=2.0, fps=30, saveas=None, output_size=None, backend="pillow", ...)	Render one image into a pan/zoom mp4.
ken_burns_film(panels, *, saveas, fps=30, audio_path=None, ...)	Render (image, path, duration_s) panels as one continuous film.