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Zoom effects create dynamic motion by scaling clips over time. MovieLite provides three zoom effect classes: ZoomIn, ZoomOut, and KenBurns.

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ZoomIn

Gradually scales up the clip from a smaller size.

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Constructor

ZoomIn(
    duration: float,
    from_scale: float = 1.0,
    to_scale: float = 1.2,
    anchor: str = "center"
)
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duration
float
required
Duration of the zoom effect in seconds, from the start of the clip.
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from_scale
float
default:"1.0"
Starting scale factor. 1.0 = 100% size (original). Minimum value is 0.1.
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to_scale
float
default:"1.2"
Ending scale factor. 1.2 = 120% size (zoomed in 20%).
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anchor
str | tuple
default:"center"
Zoom anchor point. Determines which part of the frame stays fixed during zoom.String options:
  • "center" (default)
  • "top-left", "top-right", "bottom-left", "bottom-right"
  • "top", "bottom", "left", "right"
Or a tuple (x, y) for custom anchor in clip coordinates.

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Examples

from movielite import VideoClip, vfx

# Basic zoom-in from center
clip = VideoClip("input.mp4")
clip.add_effect(vfx.ZoomIn(duration=5.0, from_scale=1.0, to_scale=1.2))

# Zoom from smaller size
clip.add_effect(vfx.ZoomIn(duration=3.0, from_scale=0.5, to_scale=1.0))

# Zoom from top-left corner
clip.add_effect(vfx.ZoomIn(duration=4.0, anchor="top-left"))

# Custom anchor point
clip.add_effect(vfx.ZoomIn(duration=5.0, anchor=(300, 200)))

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How It Works

  • Modifies both scale and position properties
  • Uses linear interpolation between from_scale and to_scale
  • Adjusts position to keep the anchor point fixed during zoom
  • After duration, maintains to_scale for remainder of clip
Source: src/movielite/vfx/zoom.py:5-71

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ZoomOut

Gradually scales down the clip.

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Constructor

ZoomOut(
    duration: float,
    from_scale: float = 1.2,
    to_scale: float = 1.0,
    anchor: str = "center"
)
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duration
float
required
Duration of the zoom effect in seconds, measured from the end of the clip.
​
from_scale
float
default:"1.2"
Starting scale factor. 1.2 = 120% size (zoomed in).
​
to_scale
float
default:"1.0"
Ending scale factor. 1.0 = 100% size (original). Minimum value is 0.1.
​
anchor
str | tuple
default:"center"
Zoom anchor point. Same options as ZoomIn.

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Examples

from movielite import VideoClip, vfx

# Basic zoom-out at end of clip
clip = VideoClip("input.mp4")
clip.add_effect(vfx.ZoomOut(duration=5.0, from_scale=1.2, to_scale=1.0))

# Zoom out to smaller size
clip.add_effect(vfx.ZoomOut(duration=3.0, from_scale=1.0, to_scale=0.7))

# Zoom out from bottom-right
clip.add_effect(vfx.ZoomOut(duration=4.0, anchor="bottom-right"))
ZoomOut applies the effect at the end of the clip, while ZoomIn applies at the start.
Source: src/movielite/vfx/zoom.py:73-144

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KenBurns

Cinematic slow zoom + pan effect named after the famous documentary filmmaker.

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Constructor

KenBurns(
    duration: float = None,
    start_scale: float = 1.0,
    end_scale: float = 1.2,
    start_position: tuple[int, int] = (0, 0),
    end_position: tuple[int, int] = (0, 0)
)
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duration
float
default:"None"
Duration of the effect in seconds. If None, uses the entire clip duration.
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start_scale
float
default:"1.0"
Starting zoom level. 1.0 = 100% size.
​
end_scale
float
default:"1.2"
Ending zoom level. 1.2 = 120% size.
​
start_position
tuple[int, int]
default:"(0, 0)"
Starting position offset as (x, y) in pixels.
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end_position
tuple[int, int]
default:"(0, 0)"
Ending position offset as (x, y) in pixels.

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Examples

from movielite import VideoClip, vfx

# Basic Ken Burns: slow zoom in
clip = VideoClip("input.mp4")
clip.add_effect(vfx.KenBurns(
    start_scale=1.0,
    end_scale=1.3
))

# Zoom and pan
clip.add_effect(vfx.KenBurns(
    duration=10.0,
    start_scale=1.0,
    end_scale=1.3,
    start_position=(0, 0),
    end_position=(-100, -50)  # Pan left and up
))

# Zoom out with pan
clip.add_effect(vfx.KenBurns(
    start_scale=1.5,
    end_scale=1.0,
    start_position=(50, 50),
    end_position=(0, 0)
))

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How It Works

  • Combines zoom (scale) and pan (position) animations
  • Uses cubic ease-in-out for smooth, cinematic motion
  • If duration is None, effect spans entire clip
  • Position offsets are relative to the clip’s base position

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Easing Function

The Ken Burns effect uses cubic ease-in-out interpolation for smoother, more natural motion: 
if progress < 0.5:
    eased = 4 × progress³
else:
    eased = 1 - (-2 × progress + 2)³ / 2
This creates slow starts and stops with faster motion in the middle. Source: src/movielite/vfx/zoom.py:146-220

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Combining Zoom Effects

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Zoom In Then Out

clip = VideoClip("input.mp4")
clip.add_effect(vfx.ZoomIn(duration=3.0, from_scale=0.8, to_scale=1.2))
clip.add_effect(vfx.ZoomOut(duration=3.0, from_scale=1.2, to_scale=0.8))
Be careful when combining ZoomIn and ZoomOut - make sure the scales align at the transition point, or you’ll get a sudden jump.

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Ken Burns with Fade

clip = VideoClip("photo.jpg", duration=10.0)
clip.add_effect(vfx.FadeIn(1.0))
clip.add_effect(vfx.KenBurns(
    duration=10.0,
    start_scale=1.0,
    end_scale=1.3,
    end_position=(-80, -60)
))
clip.add_effect(vfx.FadeOut(1.5))

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Anchor Points Reference

Visual representation of anchor point positions: 
top-left          top          top-right
    +-------------+-------------+
    |                           |
left|           center          |right
    |                           |
    +-------------+-------------+
bottom-left      bottom      bottom-right
  • center: Zoom from/to the center (most common)
  • corners: Zoom from/to a specific corner
  • edges: Zoom from/to the middle of an edge
  • custom: Specify exact (x, y) coordinates

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Performance Considerations

Zoom effects modify clip scale and position properties, not pixel data. This makes them very efficient - no image processing is required.
The Ken Burns effect’s cubic easing calculation is extremely lightweight and adds negligible overhead.

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Technical Details

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Scale Adjustments

  • Wraps the clip’s _scale function with a time-based multiplier
  • Linear interpolation for ZoomIn/ZoomOut
  • Cubic ease-in-out for KenBurns

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Position Adjustments

  • Wraps the clip’s _position function
  • Calculates offsets to keep anchor point fixed
  • Formula: offset = anchor × (1 - current_scale)

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See Also

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