# SlitScan node¶

This documentation is for version 1.0 of SlitScan (net.sf.openfx.SlitScan).

## Description¶

Apply per-pixel retiming: the time is computed for each pixel from the retime function, which can be either a horizontal ramp, a vertical ramp, or a retime map.

The default retime function corresponds to a horizontal slit: it is a vertical ramp, which is a linear function of y, which is 0 at the center of the bottom image line, and 1 at the center of the top image line. Optionally, a vertical slit may be used (0 at the center of the leftmost image column, 1 at the center of the rightmost image column), or the optional single-channel “Retime Map” input may also be used.

This plugin requires to render many frames on input, which may require a lot of memory.

Note that the results may be on higher quality if the video is slowed fown (e.g. using slowmoVideo)

The parameters are:

• retime function (default = horizontal slit)
• offset for the retime function (default = 0)
• gain for the retime function (default = -10)
• absolute, a boolean indicating that the time map gives absolute frames rather than relative frames
• frame range, only used if the retime function is given by a retime map, because the actual frame range cannot be guessed without inspecting the retime map content (default = -10..0). If “absolute” is checked, this frame range is absolute, else it is relative to the current frame
• filter to handle time offsets that “fall between” frames. They can be mapped to the nearest frame, or interpolated between the nearest frames (corresponding to a shutter of 1 frame).

References:

## Inputs¶

Input Description Optional
Source   No
Retime Map   Yes

## Controls¶

Parameter / script name Type Default Function
Retime Function / retimeFunction Choice Horizontal Slit
The function that gives, for each pixel in the image, its time. The default retime function corresponds to a horizontal slit: it is a vertical ramp (a linear function of y) which is 0 at the center of the bottom image line, and 1 at the center of the top image line. Optionally, a vertical slit may be used (0 at the center of the leftmost image column, 1 at the center of the rightmost image column), or the optional single-channel “Retime Map” input may also be used.
Horizontal Slit (horizontalslit): A vertical ramp (a linear function of y) which is 0 at the center of the bottom image line, and 1 at the center of the top image line.
Vertical Slit (verticalslit): A horizontal ramp (alinear function of x) which is 0 at the center of the leftmost image line, and 1 at the center of the rightmost image line.
Retime Map (retimemap): The single-channel image from the “Retime Map” input (zero if not connected).
Retime Offset / retimeOffset Double 0 Offset to the retime map.
Retime Gain / retimeGain Double -10 Gain applied to the retime map (after offset). With the horizontal or vertical slits, to get one line or column per frame you should use respectively (height-1) or (width-1).
Absolute / retimeAbsolute Boolean Off If checked, the retime map contains absolute time, if not it is relative to the current frame.
Max. Frame Range / frameRange Integer min: -10 max: 0 Maximum input frame range to fetch images from (may be relative or absolute, depending on the “absolute” parameter). Only used if the Retime Map is used and connected.
Filter / filter Choice Nearest
How input images are combined to compute the output image.
Nearest (nearest): Pick input image with nearest integer time.
Linear (linear): Blend the two nearest images with linear interpolation.