Alpha Over Node¶

The Alpha Over node is used to layer an image on top of another with alpha blending.
輸入¶
- Factor
The alpha of the foreground image, going from 0 (fully transparent) to 1 (fully opaque).
- 圖像
The background image.
- 圖像
前景圖像。
屬性¶
- 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.
Note
This is a legacy option.
輸出¶
- 圖像
The blended result.
範例¶
Overlay¶
In the node tree below, the Color Ramp Node 色彩漸層節點 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.

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.

Animated fade in effect using Alpha Over.¶