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Chromakey compositing node

Mask or "key" an image based on its color.

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This COP is used to mask or "key" an image based on its color. The colors keyed lie in the hue range, the saturation range and the luminance range specified. Each rolloff region extends one of the ranges with a soft rolloff function (linear, ease in, ease out, ease in ease out and gaussian).

The key plane is used to determine the areas of the image to mask. The mask is then applied to all scoped planes, including the key plane (if it is scoped). Normally this key plane is color. The color can be picked on the image by following the viewport prompts.

Scoping

This operation may be restricted to certain planes, or components of planes. In addition, the operation may be applied to a subset of frames within the sequence. An image must have both its frame and plane scoped to be modified.

Images that are not modified are passed through, which does not take any memory or processing time.

Masking

This operation may be masked, which restricts the operation to an area of the image. The mask may be inverted, brightened or dimmed.

The mask input is on the side of the node. The label on the connector indicates the plane being used as a mask.

The mask input can also be scaled to fit the output image’s resolution, if they differ. If this node is changing constantly, and the mask is not, it is somewhat faster to put a Scale COP down to do the resize for the mask image. Otherwise, the scale will occur every time this node cooks.

Parameters

Hue/Saturation

The hue and saturation ranges of colors to key. The color wheel shows the key selection.

Luminance

Defines the luminance range of the colors to key.

Discard Keyed Region

If on, the keyed region is masked out (black). Otherwise the rest of the image is masked out.

Hue Rolloff

Specifies the sharpness of the hue cutoff. This extends the hue range on either side by the rolloff size.

Saturation Rolloff

Specifies the sharpness of the saturation cutoff.

Luminance Rolloff

Specifies the sharpness of the luminance cutoff.

Rolloff Function

Specifies the rolloff function of the rolloff regions.

Supersample

The number of subpixels sampled per pixel in one direction (2 samples 4 pixels, 3 samples 9). More subsamples produce finer edges, at the cost of performance.

Key Plane

Specifies the plane to key. All scoped planes will be masked based on the result of the Chromakey on this plane.

Add Alpha if Missing

If no alpha plane exists in the input, add it and fill it with the keying mask.

Mask

A mask can be chosen to limit the effect of the operator to areas defined by the mask. The mask can be taken from the mask input (side input) or from the first input itself.

Effect Amount

If no mask is present, this blends the output with the input by a constant amount (0 = all input, 1 = all output).

If a mask is present, this amount multiplies the mask.

Operation Mask

Selects the mask plane to use as a mask from the mask input. The mask can be selected from:

A mask can be a component of a plane or an entire plane. If a vector plane is supplied as a mask, its components are multiplied by the images' components.

Scalar Mask ('A', 'C.r')

C.r = I.r * M
C.g = I.g * M
C.b = I.b * M

Vector Mask ('C')

C.r = I.r * M.r
C.g = I.g * M.g
C.b = I.b * M.b

First Input

Useful for masking the operation to the image’s own alpha plane.

Mask Input

Selects the mask from the side mask input.

Off

Turns off masking, without requiring disconnection of the mask input (useful for temporarily disabling the mask).

Resize Mask to Fit Image

If the mask image is a different resolution than the output image, turning on this parameter will scale the mask to the output image’s resolution.

If this node is changing constantly, and the mask is not, it is somewhat faster to put a Scale COP down to do the resize for the mask image. Otherwise, the scale will occur every time this node cooks.

Invert Mask

Inverts the mask so that all fully 'masked' portions become unmasked. This saves you from inserting an Invert COP after the node with the mask.

Scope

Plane Scope

Specifies the scope for both the RGB components of Color, Alpha, and other planes. The (C)RGBA mask only affects Color components and Alpha. 'C' will toggle all the RGB components.

For planes other than Color and Alpha, the plane name (plus component, if applicable) should be specified in the string field. The pulldown menu can be used to select planes or components present in this node.

A plane is specified by its name. A component is specified by both its plane and component name. The '*' wildcard may be used to scope all extra planes. Any number of planes or components can be specified, separated by spaces.

Examples:

P
N.x N.y
P N Pz

Frame Scope

Frame Scope

Allows scoping of specific frames in the frame range. This is in addition to the plane scope (so a plane at a certain frame must be both plane scoped and frame scoped to be modified).

All Frames

All frames are scoped.

Inside Range

All frames inside a subrange are scoped.

Outside Range

All frames outside a subrange are scoped.

Even Frames

Even numbered frames are scoped.

Odd Frames

Odd numbered frames are scoped.

Specific Frames

A user-defined list of frames are scoped.

Frame Range

For Inside/Outside range, this parameter specifies the subrange of the sequence to scope (or unscope). This can be edited in Timeline viewer mode (⌃ Ctrl + 2 in viewer).

Frame Dropoff

For Inside/Outside Range, this parameter specifies certain number of frames before and after to slowly ramp up to scoped. The operation will be blended with its input to 'ease in' or 'ease out' the scoping effect over a number of frames. This can be edited in Timeline viewer mode (⌃ Ctrl + 2 in viewer).

Non-scoped Effect

For unscoped frames, this sets the blend factor between the input and modified images. Normally this is zero (use the input image). By setting this to a non-zero value, you can make unscoped frames be 'slightly' unscoped. The value can vary between 0 (unscoped) and 1 (scoped).

Frame List

The frame list for 'Specific Frames'. Frame numbers should be separated by spaces.

Automatically Adjust for Length Changes

If the sequence range changes, enabling this parameter will adjust the subrange and frame dropoff lengths to fit the new range.

Locals

L

Sequence length

S

Start of sequence

E

End of sequence

IL

Input sequence length

SR

Sequence frame rate

NP

Number of planes in sequence

W,H

Width and height of image

I

Image index (0 at start frame)

IT

Image time (0 at start frame)

AI

Current plane array index

PI

Current plane index

PC

Num of channels in current plane

CXRES

Composite Project X resolution

CYRES

Composite Project Y resolution

CPIXA

Composite Project pixel aspect ratio

CDEPTH

Composite Project raster depth

CBP

Composite Project black point

CWP

Composite Project white point

Examples

The following examples include this node.

Mask Example for Blur compositing node

See also

Compositing nodes

  • Add

    Adds two images together.

  • Anaglyph

    Creates an anaglyph from a pair of input images.

  • Atop

    Composites the first input (Foreground) over the second (background), but only where the background alpha exists.

  • Average

    Averages the foreground image and the background image.

  • Blend

    Blends frames from two sequences together using a simple linear blend.

  • Blur

    Blurs an image.

  • Border

    Adds a border to the image.

  • Bright

    Applies a brightness factor and bright shift to the first input.

  • Bump

    Builds a bump map from a plane.

  • Channel Copy

    Copy channels from any of inputs into the output image.

  • Chromakey

    Mask or "key" an image based on its color.

  • Color

    Creates a constant color image.

  • Color Correct

    Applies a variety of color corrections to the image

  • Color Curve

    Adjusts the R,G,B and/or A channels based on a user-defined curve.

  • Color Map

    Maps a range of color to a new range.

  • Color Replace

    Replace a color region in an image with another region.

  • Color Wheel

    Generates a simple HSV color wheel.

  • Composite

    Does a composite (over, under, inside, add, etc) between two images.

  • Contrast

    Increases or decreases the contrast of an image.

  • Convert

    Changes the data format of a plane.

  • Convolve

    Performs a generic convolve on the source image.

  • Corner Pin

    Fits an image into an arbitrary quadrilateral.

  • Corner Ramp

    Generates a four corner ramp.

  • Crop

    Crops an image and changes its resolution.

  • Cryptomatte

    Extracts matte from Cryptomatte image.

  • DSM Flatten

    Flattens a Deep Shadow/Camera Map into a flat 2D raster.

  • Defocus

    Defocuses an image similar to a real camera defocus.

  • Deform

    Deforms an image by moving the underlying UV coordinates.

  • Degrain

    Removes film grain from an image.

  • Deinterlace

    De-interlaces a frame of video by either averaging scanlines or copying a scanline.

  • Delete

    Removes planes or components from an input sequence.

  • Denoise

    Removes white noise from an image.

  • Depth Darken

    Darkens depth boundaries in an image.

  • Depth of Field

    Creates a depth-of-field mask, which describes how out of focus parts of the image are.

  • Diff

    Computes the difference between the foreground image and the background image.

  • Dilate/Erode

    Expands and shrinks mattes.

  • Drop Shadow

    Creates a blurred shadow offset of an image.

  • Edge Blur

    Blurs the edges of an image.

  • Edge Detect

    Detects edges in the input image.

  • Emboss

    Adds a lighting effect to the image by using a bump map.

  • Environment

    Applies an environment map to an image.

  • Equalize

    Equalizes colors by stretching or shifting the image histogram.

  • Error Function Table Generator

    Creates an image containing precomputed error function terms for hair albedo computation

  • Expand

    Expands and shrinks mattes.

  • Extend

    Extends the length of a sequence so that it can be animated beyond its frame range.

  • Fetch

    Fetches a sequence of images from another COP, even in another network.

  • Field Merge

    Merges two fields into one Interlaced Frame.

  • Field Split

    Splits an interlaced frame into two fields per frame (odd and even fields).

  • Field Swap

    Swaps the two fields containing the even and odd scanlines of the frame.

  • File

    Loads image files into Houdini.

  • Flip

    Flips the image horizontally and/or vertically.

  • Fog

    Adds a variety of atmospheric effects to an image, including fog, haze and heat waves.

  • Font

    Renders anti-aliased text.

  • Front Face

    Cleans up flipped normals by making them face the camera.

  • Function

    Performs a variety of mathematical functions on the input image.

  • Gamma

    Applies gamma correction to the image.

  • Geokey

    Keys out parts of the image based on pixel position or normal direction.

  • Geometry

    Renders geometry from a SOP as a single color image.

  • Gradient

    Computes the gradient of an image.

  • Grain

    Adds grain to an image.

  • HSV

    Converts between RGB and HSV color spaces, or applies hue and saturation modifications.

  • Hue Curve

    Adjusts the saturation or luminance of the image based on hue.

  • Illegal Pixel

    Detects illegal pixels, like NAN and INF, in images.

  • Inside

    Restricts the foreground color to the area of the background’s alpha matte.

  • Interleave

    Interleaves image sequences.

  • Invert

    Applies a photographic pixel inversion to the image.

  • Layer

    Layers a series of inputs together by compositing them one by one on the background image (input 1).

  • Levels

    Adjusts black point, white point, and midrange to increase, balance, or decrease contrast.

  • Lighting

    Adds a light to the image.

  • Limit

    Limits the pixel range at the high end, low end or both.

  • Lookup

    Applies a lookup table to the input.

  • Loop

    Cooks the subnet COPs multiple times in a loop, accumulating the results.

  • Luma Matte

    Sets the alpha to the luminance of the color.

  • Lumakey

    Keys the image based on luminance (or similar function).

  • Mask

    Masks out an area of an image.

  • Max

    Outputs the maximum value of the foreground and background images for each pixel, which tends to lighten the image.

  • Median

    Applies a 3 x 3 or 5 x 5 median filter to the input image.

  • Merge

    Merges the planes of several inputs together.

  • Metadata

    Applies metadata to an image sequence.

  • Min

    Outputs the minimum value of the foreground and background images for each pixel, which tends to darken the image.

  • Mono

    Converts a color or vector into a scalar quantity, like luminance or length.

  • Mosaic

    Takes a sequence of images and combines them into 1 image by tiling them.

  • Multiply

    Multiplies the foreground image with the background image.

  • Noise

    Generates continuous noise patterns.

  • Null

    Does nothing.

  • Outside

    Restricts the foreground color to the area outside of the background’s alpha matte.

  • Over

    Composites the first input (Foreground) over the second (background).

  • Pixel

    Modifies an image’s pixels using expressions.

  • Premultiply

    Allows colour to be converted to or from a premultiplied form.

  • Pulldown

    Performs a pulldown (cine-expand) on the input sequence.

  • Pushup

    Performs a pushup (cine-expand) on the input sequence.

  • Quantize

    Quantizes input data into discrete steps.

  • ROP File Output

    Renders frames out to disk.

  • Radial Blur

    Does a radial or angular blur.

  • Ramp

    Generates a variety of linear and radial ramps, which are fully keyframable.

  • Reference

    Copies the sequence information from its input.

  • Rename

    Change the name a plane.

  • Render

    Renders a mantra output driver directly into a composite network.

  • Reverse

    Simply reverses the frames in the sequence.

  • Rotoshape

    Draws one or more curves or shapes.

  • SOP Import

    Imports a 2d Volume from SOPs as planes into a composite network.

  • Scale

    Changes the resolution of the image.

  • Screen

    Adds two images together, saturating at white like photographic addition.

  • Sequence

    Sequences two or more inputs end to end.

  • Shape

    Generates simple shapes, such as circles, stars and regular N-sided polygons.

  • Sharpen

    Sharpens an image by enhancing the contrast of edges.

  • Shift

    Shifts an image sequence in time.

  • Shuffle

    Shuffle frames around to do out-of-order editing.

  • Sky Environment Map

    Creates sky and ground images for use as environment maps.

  • Snip

    Either removes frames from a sequence or allows you to order them in a user-defined order.

  • Streak Blur

    Streaks an image, adding a motion blur effect.

  • Subnetwork

    Contains networks of other COPs.

  • Subtract

    Subtracts the foreground image from the background image.

  • Switch

    Passes the input of one of its connected inputs through, acting like an exclusive switch.

  • Switch Alpha

    Replaces input 1's alpha with input 2's alpha.

  • Terrain Noise

    Generate noise suitable for terrain height maps.

  • Tile

    Tiles the image sequence with multiple copies of the input image.

  • Time Filter

    Blurs a pixel through several frames.

  • Time Machine

    Uses a second input to time warp the first input on a per pixel basis.

  • Time Scale

    Stretches or compresses a sequence in time.

  • Time Warp

    Warps time by slowing or speeding it up throughout the sequence.

  • Transform

    Translates, rotates and/or scales the input image without changing the image resolution.

  • Trim

    Trims an input sequence in time by adjusting the beginning or the end of the sequence.

  • UV Map

    Creates a UV map.

  • Under

    Composites the first input (Foreground) under the second (background).

  • Unpin

    Extracts an arbitrary quadrilateral area out of the input image.

  • VEX Filter

    Runs a VEX script on its input planes.

  • VEX Generator

    Runs a VEX script on the planes it generates.

  • VOP COP2 Filter

    Contains a VOP network that filters input image data.

  • VOP COP2 Generator

    Contains a VOP network that generates image data.

  • Vector

    Performs vector operations on the input.

  • Velocity Blur

    Blurs an image by using pixel velocity to produce a motion blur effect.

  • Window

    Cuts a small window out of a larger image.

  • Wipe

    Does a wipe between two input sequences.

  • Xor

    Makes two elements mutually exclusive; if their alpha mattes overlap, the overlap is removed.

  • Z Comp

    Does a Z composite of two images.