feConvolveMatrix  R Documentation 
Apply a matrix convolution filter effect.
Description
A convolution combines pixels in the input image with neighbouring
pixels to produce a resulting image. A wide variety of imaging
operations can be achieved through convolutions, including blurring,
edge detection, sharpening, embossing and beveling.
Usage
feConvolveMatrix(input = NA, order = 3,
kernelMatrix = matrix(),
divisor = 1, bias = 0,
targetX = 1, targetY = 1,
edgeMode = c("duplicate", "wrap", "none"),
kernelUnitLength = NA, preserveAlpha = FALSE,
...)
Arguments
input 
Identifies an input for this filter primtive. See
filterInputs .

order 
A numeric vector of length 1 or 2. Indicates the number of cells in
each dimension for kernelMatrix . The values provided must be
integers greater than zero. The first number (orderX), indicates the
number of columns in the matrix. The second number (orderY),
indicates the number of rows in the matrix. If this is a vector of
length one then the number of rows is assumed to be same as the
number of columns specified.

kernelMatrix 
The kernel matrix for the convolution. The number of entries must
correspond with the values given by order .

divisor 
After applying the kernelMatrix to the input image to yield a
number, that number is divided by divisor to yield the final
destination colour value. A divisor that is the sum of all the
matrix values tends to have an evening effect on the overall colour
intensity of the result. It is an error to specify a divisor of
zero. The default value is the sum of all values in kernelMatrix,
with the exception that if the sum is zero, then the divisor is set
to 1.

bias 
After applying the kernelMatrix to the input image to yield a
number and applying the divisor , the bias attribute is
added to each component. One application of bias is when it
is desirable to have 0.5 gray value be the zero response of the
filter. The bias property shifts the range of the filter. This
allows representation of values that would otherwise be clamped to 0
or 1.

targetX 
Determines the positioning in X of the convolution matrix relative
to a given target pixel in the input image. The leftmost column of
the matrix is column number zero. The value must be such that:
0 <= targetX < orderX. By default, the
convolution matrix is centered in X over each pixel of the input
image (i.e., targetX =
floor( orderX / 2 )).

targetY 
Determines the positioning in Y of the convolution matrix relative
to a given target pixel in the input image. The topmost row of the
matrix is row number zero. The value must be such that: 0 <= targetY < orderY. By default, the
convolution matrix is centered in Y over each pixel of the input
image (i.e., targetY =
floor( orderY / 2)).

edgeMode 
Determines how to extend the input image as necessary with colour
values so that the matrix operations can be applied when the kernel
is positioned at or near the edge of the input image.

"duplicate" indicates that the input image is
extended along each of its borders as necessary by duplicating the
colour values at the given edge of the input image.

"wrap" indicates that the input image is extended by
taking the colour values from the opposite edge of the image.

"none" indicates that the input image is extended
with pixel values of zero for R, G, B and A.

kernelUnitLength 
The first number is the dx value. The second number is the
dy value. If the dy value is not specified, it
defaults to the same value as dx . Indicates the intended
distance in current filter units (i.e., units as determined by the
value of the filter effect container's primitiveUnits )
between successive columns and rows, respectively, in the
kernelMatrix . By specifying value(s) for
kernelUnitLength , the kernel becomes defined in a scalable,
abstract coordinate system. If kernelUnitLength is not
specified, the default value is one pixel in the offscreen bitmap,
which is a pixelbased coordinate system, and thus potentially not
scalable.

preserveAlpha 
A value of FALSE indicates that the convolution will apply to
all channels, including the alpha channel.
A value of TRUE indicates that the convolution will only
apply to the colour channels. In this case, the filter will
temporarily unpremultiply the colour component values, apply the
kernel, and then repremultiply at the end.

... 
Further arguments to be passed onto fe .

Details
For more information about this primitive, consult the reference to
the SVG specification.
Value
An fe.convolve.matrix
object.
Author(s)
Simon Potter
References
http://www.w3.org/TR/SVG/filters.html#feConvolveMatrixElement
See Also
filterEffect
, fe
.