feConvolveMatrix Filter Element¶
feConvolveMatrix applies a matrix convolution filter effect. A convolution combines pixels in the input image with neighboring 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.
For common properties see: Filter Primitives Overview
in – (see in attribute)
order – <number-optional-number>
Indicates the number of cells in each dimension for kernelMatrix. The values provided must be <integer>`s 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 <orderY> is not provided, it defaults to <orderX>.
If the attribute is not specified, the effect is as if a value of 3 were specified.
kernelMatrix – <list of numbers>
The list of <number>`s that make up the kernel matrix for the convolution. Values are separated by space characters and/or a comma. The number of entries in the list must equal `<orderX> times <orderY>.
divisor – <number>
After applying the kernelMatrix to the input image to yield a number, that number is divided by divisor to yield the final destination color value. 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 = <number>
After applying the kernelMatrix to the input image to yield a number and applying the divisor, the bias attribute is added to each component.
targetX – <integer>
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 – <integer>
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 )).
'duplicate | wrap | none'
Determines how to extend the input image as necessary with color 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 color values at the given edge of the input image.
'wrap'indicates that the input image is extended by taking the color 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.
If attribute edgeMode is not specified, then the effect is as if a value of
kernelUnitLength – <number-optional-number>
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 attribute 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 pixel-based coordinate system, and thus potentially not scalable. For some level of consistency across display media and user agents, it is necessary that a value be provided for at least one of filterRes and kernelUnitLength. In some implementations, the most consistent results and the fastest performance will be achieved if the pixel grid of the temporary offscreen images aligns with the pixel grid of the kernel. A negative or zero value is an error.
'false | true'
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 color channels. In this case, the filter will temporarily unpremultiply the color component values, apply the kernel, and then re-premultiply at the end.
If preserveAlpha is not specified, then the effect is as if a value of