The Keyer node can be used to generate a mask using a colour-key to assist with operations such as automatic feature tracking. After creating a Keyer node, it can be attached to any other node that has a purple indicator on an input label.
Keyer nodes can only be connected to a single mask indicator on another node.
Keyer masks are defined by one or more Sample positions. Each sample position captures a colour from the image, and defines both a Colour Falloff and Spatial Similarity value. The overall mask is created by identifying which pixels are similar to the samples in terms of their colour and spatial matches.
The position and colour falloff can be animated over the entire clip if required. Frames where the current sample point is keyframed are displayed with yellow markers in the scrub bar.
Increasing the Colour Falloff value (the vertical slider) will mean that more pixels are included in the mask.
The following image shows the difference between a low falloff value on the left, and a high falloff value on the right:
Adjusting the Spatial Similarity will affect the roughness of the mask border.
Decreasing the Spatial Similarity to zero, however, will remove all spatial awareness from the sample point, meaning it operates with colour values alone. This means disconnected parts of the image can be added to the mask without the need to create more sample points, as shown in the following image where the areas inside the actor's arms are now part of the mask:
(Footage courtesy of http://www.hollywoodcamerawork.com/green-screen-plates.html)
Sample: Create a new sample point at the centre of the image. The position of the sample point can be adjusted by clicking and dragging the centre point with the left mouse button.
The Colour Falloff and Spatial Similarity values can be adjusted by dragging the vertical and horizontal handles respectively.
K-, K+: Move to the previous or next frame that contains a sample keyframe.
R-: Remove all earlier keyframes (relative to the current frame) from the sample.
Remove Key: Remove a keyframe at the current frame from the sample.
R+ Remove all later keyframes (relative to the current frame) from the sample.
In: Set the in-point of the selected sample to the current frame. The in-point can also be changed using the edit box. The R button will reset the in-point to the start of the clip.
Out: Set the out-point of the selected sample to the current frame. The out-point can also be changed using the edit box. The R button will reset the out-point to the end of the clip.
Cut: Copy selected samples into the clipboard and delete it from the sample list.
Copy: Copy selected samples into the clipboard, so they can then be pasted into a different Keyer node.
Paste: Paste masks stored in the clipboard into the Keyer node.
Duplicate: Duplicate all selected samples.
Invert: Invert the entire mask.
Marquee: Allow samples to be selected by clicking and dragging with the left mouse button in the main image window. Hold the Shift key whilst drawing to ensure that previous selections are kept. Holding the Ctrl key will allow a lasso selection to be used instead of a rectangle.
All/None: Select all or none of the samples in the list.
Lock/Unlock: Lock or unlock all selected samples. Locked samples cannot be edited.
Delete: Delete all selected samples from the list.
Colour and Opacity: Double-clicking on the colour button will display a colour chooser dialog that allows the default colour of new samples to be changed. The opacity edit box can also be used to adjust overall mask opacity, allowing more or less of the background image to show through. Note that mask opacity does not affect how much each pixel is masked: it is used only for display purposes.
Keyboard shortcuts can be customised in the Preferences.
|Remove Earlier Keys
|Remove Later Keys
|Move To Previous Keyframe
|Move To Next Keyframe