Alpha上叠节点

Alpha上叠节点。

The Alpha Over node is used to layer images on top of one another. Where the foreground image pixels have an alpha greater than 0, it will be overlaid over the background image.

输入

系数

Controls the transparency of the foreground image. A factor less than 1 will make the foreground more transparent.

图像

背景 图像输入端。

图像

前景 图像的输入

属性

转换预乘

将前景图像转为预乘alpha格式。

The Alpha Over node is designed to work with premultiplied alpha color format. Use Convert Premul when you know that your image has straight alpha color values, to perform the correct over operation. Result will still be premultiplied alpha.

见 Alpha通道。

预乘

Premul 滑块允许在使用 预乘 或 非预乘 alpha 之间进行混合。

设置为 1 时，前景颜色值将乘以 alpha，即预乘。这相当于启用 转换预乘 选项。设置为 0 时，颜色值不会更改。

如果 [预乘] 不是零，则 转换预乘 将被忽略。

Note

这是一个旧版选项。

输出

图像

标准化图像输出。

范例

Overlay

In the node tree below, Color Ramp node is used to add an alpha channel to the black-and-white swirl image. Then Alpha Over node is used to overlay it on top of another image.

使用Alpha上叠节点合成图像。

Fade In

In the next example, the Factor is used to make a “Fade In” effect. This effect can be animated by adding a Time node to feed the Factor socket as shown below. Over the course of 30 frames, the Alpha Over node outputs a image that starts with the pure background image, and the title slowly appearing.

使用alpha上叠的动画淡出效果。

请注意 转换预乘 复选框被启用，因为前景使用具有 直通型 alpha 的 PNG 图像。