Shape Alpha (Mask)¶

Description

This effect essentially works like the Shape Alpha effect but takes a snapshot of the frame before it draws simple shapes into the alpha channel. Use it together with the Mask Apply effect that uses a transition to composite the current frame’s image over the snapshot. The typical use case is to add effects in the following sequence:

Alpha Shapes Mask (this effect) –> zero or more effects (e.g. Blur, Cartoon) –> Mask Apply [–> more effects if needed]

Parameters

Parameter	Value	Description
Image or video resource	File Selection	Select the file (image or video) to be used as the mask
Threshold	Percentage	Sets the threshold for making opaqueness and transparency. Values below the value are made opaque, values above transparent.
Softness	Float	When using Threshold determines how soft to make the edge around the threshold. Similar to feathering. 0.0 means no softness (hard edge), 1.0 means very soft (default is 0.10).
Invert	Switch	Invert the alpha channel
Use Luma	Switch	Use the Luma information instead of the alpha channel
Use Threshold	Switch	Use the Threshold value

Notes

You can use a static image file or a video for animated masks

Examples

kdenlive2304_effects-shape_alpha_resource — Shape Alpha selecting the resource¶

Select the file you want to use for the mask

kdenlive2304_effects-shape_alpha_error — Shape Alpha error message in case no alpha¶

If the selected image or video file does not have an alpha channel, Kdenlive displays this warning message

kdenlive2304_effects-shape_alpha_luma — Shape Alpha using Luma information¶

Instead of the alpha channel you can use the Luma information in the file

This is an example for how the Shape Alpha effect looks like when using a PGM image file with Luma: