Alpha Over Node¶

The Alpha Over node is used to layer an image on top of another with alpha blending.

Inputs¶

Factor: The alpha of the foreground image, going from 0 (fully transparent) to 1 (fully opaque).
Image: The background image.
Image: The foreground image.

Properties¶

Convert Premultiplied

The Alpha Over node expects the foreground image to use Premultiplied Alpha. If it uses Straight Alpha instead, you can enable this checkbox to convert it.

Premultiplied

Interpolate between Premultiplied Alpha and Straight Alpha.

When set to 1, the foreground color values will be multiplied by the alpha; this is equivalent to enabling Convert Premultiplied. When set to 0, the color values do not change.

If Premultiplied is not zero, Convert Premultiplied will be ignored.

Muista

This is a legacy option.

Outputs¶

Image: The blended result.

Examples¶

Overlay¶

In the node tree below, the Color Ramp Node is used to convert an opaque, grayscale swirl image to a red one with transparency. Then, the Alpha Over node is used to overlay it on top of another image.

../../../../_images/compositing_types_converter_color-ramp_create-alpha-mask.png — Assembling a composite image using Alpha Over.¶

Fade In¶

The example below uses the Time Curve Node to gradually increase the Alpha Over node’s Factor from 0 to 1 over the course of 30 frames. This will result in the text fading in on top of the background image.

../../../../_images/compositing_types_color_alpha-over_example.png — Animated fade in effect using Alpha Over.¶