W3cubDocs

/SVG

<feConvolveMatrix>

The <feConvolveMatrix> SVG filter primitive 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.

A matrix convolution is based on an n-by-m matrix (the convolution kernel) which describes how a given pixel value in the input image is combined with its neighboring pixel values to produce a resulting pixel value. Each result pixel is determined by applying the kernel matrix to the corresponding source pixel and its neighboring pixels. The basic convolution formula which is applied to each color value for a given pixel is:

COLORX,Y = ( SUM I=0 to [orderY-1] { SUM J=0 to [orderX-1] { SOURCE X-targetX+J, Y-targetY+I * kernelMatrixorderX-J-1, orderY-I-1 } } ) / divisor + bias * ALPHAX,Y

where "orderX" and "orderY" represent the X and Y values for the 'order' attribute, "targetX" represents the value of the 'targetX' attribute, "targetY" represents the value of the 'targetY' attribute, "kernelMatrix" represents the value of the 'kernelMatrix' attribute, "divisor" represents the value of the 'divisor' attribute, and "bias" represents the value of the 'bias' attribute.

Note in the above formulas that the values in the kernel matrix are applied such that the kernel matrix is rotated 180 degrees relative to the source and destination images in order to match convolution theory as described in many computer graphics textbooks.

To illustrate, suppose you have an input image which is 5 pixels by 5 pixels, whose color values for one of the color channels are as follows:

0    20  40 235 235
100 120 140 235 235
200 220 240 235 235
225 225 255 255 255
225 225 255 255 255

and you define a 3-by-3 convolution kernel as follows:

1 2 3
4 5 6
7 8 9

Let's focus on the color value at the second row and second column of the image (source pixel value is 120). Assuming the simplest case (where the input image's pixel grid aligns perfectly with the kernel's pixel grid) and assuming default values for attributes 'divisor', 'targetX' and 'targetY', then resulting color value will be:

(9*0   + 8*20  + 7*40 +
 6*100 + 5*120 + 4*140 +
 3*200 + 2*220 + 1*240) / (9+8+7+6+5+4+3+2+1)

Usage context

Categories Filter primitive element
Permitted content Any number of the following elements, in any order:
<animate>, <set>

Attributes

Global attributes

Specific attributes

DOM Interface

This element implements the SVGFEConvolveMatrixElement interface.

Example

SVG

<svg
  width="200"
  height="200"
  viewBox="0 0 200 200"
  xmlns="http://www.w3.org/2000/svg"
  xmlns:xlink="http://www.w3.org/1999/xlink">
  <defs>
    <filter id="emboss">
      <feConvolveMatrix
        kernelMatrix="3 0 0
                      0 0 0
                      0 0 -3" />
    </filter>
  </defs>

  <image
    xlink:href="mdn.svg"
    x="0"
    y="0"
    height="200"
    width="200"
    style="filter:url(#emboss);" />
</svg>

Result

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
feConvolveMatrix Yes 12 Yes Yes Yes No Yes Yes Yes No No Yes
bias No No No No No No No No No No No No
divisor No No No No No No No No No No No No
edgeMode No No No No No No No No No No No No
in Yes 12 Yes Yes Yes No Yes Yes Yes No No Yes
kernelMatrix Yes 12 Yes Yes Yes No Yes Yes Yes No No Yes
kernelUnitLength No No No No No No No No No No No No
order No No No No No No No No No No No No
preserveAlpha No No No No No No No No No No No No
targetX No No No No No No No No No No No No
targetY No No No No No No No No No No No No

See also

© 2005–2023 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/SVG/Element/feConvolveMatrix