jit.chromakey
Description
Produces an chromakey effect based on a reference color. Tolerance and fade settings allow for control over the resulting combined image. An alternate mode outputs a matrix with the keying values, which can be used by other Jitter objects.
Examples
Discussion
The jit.chromakey object measures the chromatic distance of each of the left input's cells (pixels) with a reference color (a.k.a "green screening"). The total chromatic distance is calculated by summing the absolute value of each color channel's distance from the reference color's corresponding color channel.
If the distance is less than or equal to a tolerated distance (tol) value, the right input cell is multiplied by a maximum keying (maxkey) value.
If the distance is greater than the tolerated distance but less than the sum of the tolerated value and a set fade value (fade) an interpolated value between the some value between minkey and maxkey values is applied.
For values whose distance is greater than the sum of the tolerated and fade values, the right input cell is multiplied by the minkey value.
The left input is always multiplied by the additive inverse of the left input's multiplicand.
The jit.chromakey object has two modes of output; the first keys between the two input sources, and the second mode will output the keying values (i.e., the left input multiplicands) rather than applying the keying -- the left input is ignored. This is useful for outputting keying information for use with other Jitter objects. Keying can be inverted by swapping the minkey and maxkey values.
Matrix Operator
| Name | IOProc | Planelink | Typelink | Dimlink | Plane | Dim | Type |
|---|---|---|---|---|---|---|---|
| in2 | resamp | 1 | 1 | 1 | 1 | 1 | char long float32 float64 |
| out | n/a | 1 | 1 | 1 | 1 | 1 | char long float32 float64 |
More about Matrix Operators
The Jitter MOP
Since the matrix is Jitter's focus, it is not surprising that the majority of Jitter objects fall in this category of Matrix Operators. Every Matrix operator has some number of matrix inputs and some number of matrix outputs. Matrix inputs are referred to by the names "in", "in2", "in3", etc., from left to right, and matrix outputs are referred to by the names "out", "out2", "out3", etc., from left to right--i.e. the names are appended by the input/output number except for the first (leftmost) input and first (leftmost) output which are simply named "in" and "out". We will refer to the input or output name names as the "I/O-name".
Matrix inputs and outputs typically each have their own matrices internally where information is kept. This is necessary because Jitter is an asynchronous framework (i.e. all the matrices don't arrive at all inputs at the same time). Various aspects of matrix inputs and outputs can be set using the command [I/O-name] combined with one of the following suffixes: "_dim" which will set the dimensions of the specified I/O matrix, "_type" which will set the type of the specified matrix, "_planecount" which will set the plane of the specified matrix, or "_name" which will set the name of the specified matrix. There is one special case which does not have an internal matrix and this is the first input "in". This is the case since this special input actually triggers the calculation of the matrix operator, so it doesn't need to be cached until a calulation takes place, unlike the other inputs. Therefore there is no mechanism to set the dim, planecount, type, or name of "in".
Matrix operators accept what we'll refer to as "matrix args"--i.e. [planecount (int)] [ type (symbol)] [dim (int list)]. if these arguments are present, the adapt attribute will be turned off, otherwise it will be turned on. If adapt mode is turned on, each time a matrix is received in the first input, there will also be the equivalent of setting the dim, planecount, and type attributes to that of the input matrix. If the other inputs and outputs are linked to these attributes, this will affect their linked attributes as well. See the "MOP" table to determine which inputs and outputs will be linked to which attributes when adapt mode is turned on. For the leftmost input this is not applicable, and hence all columns are labelled "n/a".
The jit.matrix object is a named matrix which may be used to matrix data storage and retrieval, resampling, and matrix type and planecount conversion operations.
MOP Arguments
planecount [int]
Explicitly sets the number of planes for the output and any righthand inputs. If this is absent, the Matrix Operator will typically adapt to the lefthand incoming matrix attributes, except for special case operators.
type [symbol]
Explicitly sets the type of the matrix for the output and any righthand inputs. If this is absent, the Matrix Operator will typically adapt to the lefthand incoming matrix attributes, except for special case operators.
dimensions [list]
Explicitly sets the dimensions of the matrix for the output and any righthand inputs. If this is absent, the Matrix Operator will typically adapt to the lefthand incoming matrix attributes, except for special case operators.
MOP Attributes
adapt [int]
Matrix adaptation flag (default = 0 if matrix arguments are present, otherwise 1) When the flag is set, the jit.matrix object will adapt to the incoming matrix planecount, type, and dimensions.
[in/out]_dim [32 ints]
The matrix data dimensions (default = 1 1)
[in/out]_name [symbol]
The input or output name of the matrix (default = UID)
[in/out]_planecount [int]
The number of planes in matrix input our output data. Except in special cases, this value is equal to the planecount.
[in/out]_type [symbol]
The input or output matrix data type. Except in special cases, this value is equal to type.
outputmode [int]
Output mode (default = 1 (calculate and output matrix))
0 = No output (no calculation)
1 = Calculate and output the matrix
2 = Pass input (no calculation)
3 = Pass output (no calculation)
type [int]
The matrix data type (default = char
Supported data types are char, long, float32, or float64.
MOP Messages
bang
clear
exportattrs
Arguments
getattributes
getstate
importattrs
Arguments
jit_matrix
Arguments
outputmatrix
summary
Attributes
alphaignore [int]
Ignore alpha channel flag (default = 1)
0 = use alpha channel (plane 0) when calculating chromatic distance
1 = ignore alpha channel (plane 0) when calculating chromatic distance
color [32 floats]
The reference color to be used for keying (default = all 0.)
fade [float]
The amount of fade (default = 0.)
maxkey [float]
The maximum keying value (default = 1.)
minkey [float]
Minimum keying value
mode [int]
Output mode (default = 0)
0 = perform keying and output matrix
1 = output the key map for use elsewhere
2 = alpha contains key map, other planes are from left input
Possible values:
0 = 'Composite'
1 = 'Key Map in All Channels'
2 = 'Key Map in Alpha'
tol [float]
The tolerated distance -- the range of variance from which an input cell's absolute value can diverge when calculating keying (default = 0.)
Common Box Attributes
annotation [symbol]
Sets the text that will be displayed in the Clue window when the user moves the mouse over the object.
background [int] (default: 0)
Adds or removes the object from the patcher's background layer. background 1 adds the object to the background layer, background 0 removes it. Objects in the background layer are shown behind all objects in the default foreground layer.
color [4 floats]
Sets the color for the object box outline.
fontface [int]
Sets the type style used by the object. The options are:
plain
bold
italic
bold italic
Possible values:
0 = 'regular'
1 = 'bold'
2 = 'italic'
3 = 'bold italic'
fontname [symbol]
Sets the object's font.
fontsize [float]
Sets the object's font size (in points).
Possible values:
'8'
'9'
'10'
'11'
'12'
'13'
'14'
'16'
'18'
'20'
'24'
'30'
'36'
'48'
'64'
'72'
hidden [int] (default: 0)
Toggles whether an object is hidden when the patcher is locked.
hint [symbol]
Sets the text that will be displayed in as a pop-up hint when the user moves the mouse over the object in a locked patcher.
ignoreclick [int] (default: 0)
Toggles whether an object ignores mouse clicks in a locked patcher.
jspainterfile [symbol]
JS Painter File
patching_rect [4 floats] (default: 0. 0. 100. 0.)
Sets the position and size of the object in the patcher window.
position [2 floats]
Sets the object's x and y position in both patching and presentation modes (if the object belongs to its patcher's presentation), leaving its size unchanged.
presentation [int] (default: 0)
Sets whether an object belongs to the patcher's presentation.
presentation_rect [4 floats] (default: 0. 0. 0. 0.)
Sets the x and y position and width and height of the object in the patcher's presentation, leaving its patching position unchanged.
rect [4 floats]
Sets the x and y position and width and height of the object in both patching and presentation modes (if the object belongs to its patcher's presentation).
size [2 floats]
Sets the object's width and height in both patching and presentation modes (if the object belongs to its patcher's presentation), leaving its position unchanged.
textcolor [4 floats]
Sets the color for the object's text in RGBA format.
textjustification [int]
Sets the justification for the object's text.
Possible values:
0 = 'left'
1 = 'center'
2 = 'right'
varname [symbol]
Sets the patcher's scripting name, which can be used to address the object by name in pattr, scripting messages to thispatcher, and the js object.
See Also
| Name | Description |
|---|---|
| Working with Video in Jitter | Working with Video in Jitter |
| jit.alphablend | Blend two images with an alpha channel image |
| jit.keyscreen | Choke chromakey from 3 sources |
| jit.lumakey | Key based on distance from a luminance value |
| jit.op | Apply binary or unary operators |
| Tutorial 10: Chromakeying | Tutorial 10: Chromakeying |