SVG Filters 1.2, Part 2: Language

Abstract

SVG is language for describing vector graphics, however it's typically rendered on raster displays. SVG filter effects is a way of processing the generated raster image before it's displayed.

Although originally designed for use in SVG, filter effects are defined in XML and are accessed via a presentation property, and therefore could be used in other environments, such as HTML styled with CSS and XSL:FO.

This document defines the markup used by SVG filters.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This document is the First Public Working Draft of this specification. There is an accompanying SVG Filters 1.2, Part 1: Primer that lists the ways SVG filters may be used.

This document has been produced by the W3C SVG Working Group as part of the W3C Graphics Activity within the Interaction Domain. The Working Group expects to advance this Working Draft to Recommendation Status.

We explicitly invite comments on this specification. Please send them to www-svg@w3.org: the public email list for issues related to vector graphics on the Web (archives). Acceptance of the archiving policy is requested automatically upon first post to the list. To subscribe send an email to www-svg-request@w3.org with the word subscribe in the subject line.

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

How to read this document and give feedback

This draft of SVG Filters is essentially the filter chapter from SVG 1.1. One of the goals is that this specification can be re-used more easily by other specifications that want to have filter effects. Some things that have been changed are: error handling is more similar to SVG Tiny 1.2, the addition of a 'feDropShadow' filter primitive and the possibility to filter bitmap data with the DOM.

Sections have been marked with green sidebars if it's new since SVG 1.1, and in blue if it's been changed since SVG 1.1.

The main purpose of this document is to encourage public feedback. The best way to give feedback is by sending an email to public-svg-filters@w3.org. Please include some kind of keyword that identifies the area of the specification the comment is referring to in the subject line of your message (e.g "Section X.Y - the 'filter' property" or "Filtering primitive handling"). If you have comments on multiple areas of this document, then it is probably best to split those comments into multiple messages.

The public are welcome to comment on any aspect in this document, but there are a few areas in which the SVG Working Group are explicitly requesting feedback. These areas are noted in place within this document. There is also a specific area related to the specification that is listed here:

Table of Contents

• 1 Introduction
• 2 The 'filter'element
• 3 The 'filter'property
• 4 Filter effects region
  • 4.1 Filter Region extensions
• 5 Accessing the background image
  • 5.1 Accessing the background image in SVG
• 6 Filter primitives overview
  • 6.1 Overview
  • 6.2 Common attributes
  • 6.3 Filter primitive subregion
• 7 Light source elements and properties
  • 7.1 Introduction
  • 7.2 Light source 'feDistantLight'
  • 7.3 Light source 'fePointLight'
  • 7.4 Light source 'feSpotLight'
  • 7.5 The 'lighting-color' property
• 8 Filter primitive 'feBlend'
• 9 Filter primitive 'feColorMatrix'
• 10 Filter primitive 'feComponentTransfer'
• 11 Filter primitive 'feComposite'
• 12 Filter primitive 'feConvolveMatrix'
• 13 Filter primitive 'feDiffuseLighting'
• 14 Filter primitive 'feDisplacementMap'
• 15 Filter primitive 'feFlood'
• 16 Filter primitive 'feGaussianBlur'
• 17 Filter primitive 'feImage'
• 18 Filter primitive 'feMerge'
• 19 Filter primitive 'feMorphology'
• 20 Filter primitive 'feOffset'
• 21 Filter primitive 'feSpecularLighting'
• 22 Filter primitive 'feTile'
• 23 Filter primitive 'feTurbulence'
• 24 Filter primitive 'feDropShadow'
• 25 Filter primitive 'feDiffuseSpecular'
• 26 Filter primitive 'feCustom'
• 27 RelaxNG Schema for SVG Filters 1.2
• 28 DOM interfaces
  • 28.1 Interface ImageData
  • 28.2 Interface SVGFilterElement
  • 28.3 Interface SVGFilterPrimitiveStandardAttributes
  • 28.4 Interface SVGFEBlendElement
  • 28.5 Interface SVGFEColorMatrixElement
  • 28.6 Interface SVGFEComponentTransferElement
  • 28.7 Interface SVGComponentTransferFunctionElement
  • 28.8 Interface SVGFEFuncRElement
  • 28.9 Interface SVGFEFuncGElement
  • 28.10 Interface SVGFEFuncBElement
  • 28.11 Interface SVGFEFuncAElement
  • 28.12 Interface SVGFECompositeElement
  • 28.13 Interface SVGFEConvolveMatrixElement
  • 28.14 Interface SVGFEDiffuseLightingElement
  • 28.15 Interface SVGFEDistantLightElement
  • 28.16 Interface SVGFEPointLightElement
  • 28.17 Interface SVGFESpotLightElement
  • 28.18 Interface SVGFEDisplacementMapElement
  • 28.19 Interface SVGFEFloodElement
  • 28.20 Interface SVGFEGaussianBlurElement
  • 28.21 Interface SVGFEImageElement
  • 28.22 Interface SVGFEMergeElement
  • 28.23 Interface SVGFEMergeNodeElement
  • 28.24 Interface SVGFEMorphologyElement
  • 28.25 Interface SVGFEOffsetElement
  • 28.26 Interface SVGFESpecularLightingElement
  • 28.27 Interface SVGFETileElement
  • 28.28 Interface SVGFETurbulenceElement
  • 28.29 Interface SVGFEDropShadowElement
• 29 References
  • 29.1 Normative References
  • 29.2 Informative References

1 Introduction

This chapter describes a declarative filter effects feature set, which when combined with the other web technologies, like SVG or HTML, can describe much of the common artwork on the Web in such a way that client-side generation and alteration can be performed easily. In addition, the ability to apply filter effects to SVG graphics elements and container elements helps to maintain the semantic structure of the document, instead of resorting to images which aside from generally being a fixed resolution tend to obscure the original semantics of the elements they replace. This is especially true for effects applied to text. The various usage scenarios are listed in the SVG Filters Requirements document.

Note that even though this specification references parts of SVG 1.1 it does not require a complete SVG 1.1 implementation.

This document is normative.

This document contains explicit conformance criteria that overlap with some RNG definitions in requirements. If there is any conflict between the two, the explicit conformance criteria are the definitive reference.

A filter effect consists of a series of graphics operations that are applied to a given source graphic to produce a modified graphical result. The result of the filter effect is rendered to the target device instead of the original source graphic. The following illustrates the process:

2 The 'filter' element

The description of the 'filter' element follows:

Properties inherit into the 'filter' element from its ancestors; properties do not inherit from the element referencing the 'filter' element.

'filter' elements are never rendered directly; their only usage is as something that can be referenced using the 'filter' property. The 'display' property does not apply to the 'filter' element; thus, 'filter' elements are not directly rendered even if the 'display' property is set to a value other than none, and 'filter' elements are available for referencing even when the 'display' property on the 'filter' element or any of its ancestors is set to none.

3 The 'filter' property

The description of the 'filter' property is as follows:

<FuncXMLRI>

An IRI reference to a 'filter' element which defines the filter effects that shall be applied to this element.

none

Do not apply any filter effects to this element.

4 Filter effects region

A 'filter' element can define a region on the canvas to which a given filter effect applies and can provide a resolution for any intermediate continuous tone images used to process any raster-based filter primitives.

	<filter id="dropShadow" x="0" y="0" width="1" height="1"
			  filterMarginUnits="userSpaceOnUse"
			  mx="0" my="0" mw="5" mh="5" >
		  <feGaussianBlur stdDeviation="2" in="SourceAlpha" />
		  <feOffset dx="2" />
		  <feMerge>
			   <feMergeNode />
			   <feMergeNode in="SourceGraphic" />
		  </feMerge>
	</filter> 

The 'filter' element has the following attributes which work together to define the filter effects region:

• filterUnits={ userSpaceOnUse | objectBoundingBox }.
  
  Defines the coordinate system for attributes x, y, width, height.
  
  If filterUnits="userSpaceOnUse", x, y, width, height represent values in the current user coordinate system in place at the time when the 'filter' element is referenced (i.e., the user coordinate system for the element referencing the 'filter' element via a 'filter' property).
  
  If filterUnits="objectBoundingBox", then x, y, width, height represent fractions or percentages of the bounding box on the referencing element (see Object bounding box units ).
  
  If attribute filterUnits is not specified, then the effect is as if a value of objectBoundingBox were specified.
  
  Animatable:yes.
• x, y, width, height, which define a rectangular region on the canvas to which this filter applies.
  
  The amount of memory and processing time required to apply the filter are related to the size of this rectangle and the filterRes attribute of the filter.
  
  The coordinate system for these attributes depends on the value for attribute filterUnits.
  
  The bounds of this rectangle act as a hard clipping region for each filter primitive included with a given 'filter' element; thus, if the effect of a given filter primitive would extend beyond the bounds of the rectangle (this sometimes happens when using a 'feGaussianBlur' filter primitive with a very large stdDeviation), parts of the effect will get clipped.
  
  If x or y is not specified, the effect is as if a value of "-10%" were specified.
  
  If width or height is not specified, the effect is as if a value of "120%" were specified.
  
  Negative or zero values for width or height disable rendering of the element which referenced the filter.
  
  Animatable:yes.

• filterRes (which has the form x-pixels [y-pixels]) indicates the width and height of the intermediate images in pixels. If not provided, then a reasonable default resolution appropriate for the target device will be used. (For displays, an appropriate display resolution, preferably the current display's pixel resolution, is the default. For printing, an appropriate common printer resolution, such as 400dpi, is the default.)
  
  Care should be taken when assigning a non-default value to this attribute. Too small of a value may result in unwanted pixelation in the result. Too large of a value may result in slow processing and large memory usage.
  
  Negative or zero values disable rendering of the element which referenced the filter.
  
  Animatable:yes.

Note that both of the two possible value for filterUnits (i.e., objectBoundingBox and userSpaceOnUse) result in a filter region whose coordinate system has its X-axis and Y-axis each parallel to the X-axis and Y-axis, respectively, of the user coordinate system for the element to which the filter will be applied.

Sometimes implementers can achieve faster performance when the filter region can be mapped directly to device pixels; thus, for best performance on display devices, it is suggested that authors define their region such that the user agent can align the filter region pixel-for-pixel with the background. In particular, for best filter effects performance, avoid rotating or skewing the user coordinate system. Explicit values for attribute filterRes can either help or harm performance. If filterRes is smaller than the automatic (i.e., default) filter resolution, then filter effect might have faster performance (usually at the expense of quality). If filterRes is larger than the automatic (i.e., default) filter resolution, then filter effects performance will usually be slower.

It is often necessary to provide padding space because the filter effect might impact bits slightly outside the tight-fitting bounding box on a given object. For these purposes, it is possible to provide negative percentage values for x, y and percentages values greater than 100% for width, height. This, for example, is why the defaults for the filter effects region are x="-10%" y="-10%" width="120%" height="120%".

5 Accessing the background image

Two possible pseudo input images for filter effects are BackgroundImage and BackgroundAlpha, which each represent an image snapshot of the canvas under the filter region at the time that the 'filter' element is invoked. BackgroundImage represents both the color values and alpha channel of the canvas (i.e., RGBA pixel values), whereas BackgroundAlpha represents only the alpha channel.

Implementations will often need to maintain supplemental background image buffers in order to support the BackgroundImage and BackgroundAlpha pseudo input images. Sometimes, the background image buffers will contain an in-memory copy of the accumulated painting operations on the current canvas.

Because in-memory image buffers can take up significant system resources, content must explicitly indicate to the user agent that the document needs access to the background image before BackgroundImage and BackgroundAlpha pseudo input images can be used.

The property which enables access to the background image is 'enable-background':

Assume you have an element E in the document and that E has a series of ancestors A₁ (its immediate parent), A₂, etc. (Note: A₀ is E.) Each ancestor A_i will have a corresponding temporary background image offscreen buffer BUF_i. The contents of the background image available to a 'filter' referenced by E is defined as follows:

• Find the element A_i with the smallest subscript i (including A₀=E) for which the 'enable-background' property has the value new. (Note: if there is no such ancestor element, then there is no background image available to E, in which case a transparent black image will be used as E's background image.)
• For each A_i (from i=n to 1), initialize BUF_i to transparent black. Render all children of A_i up to but not including A_i-1 into BUF_i. The children are painted, then filtered, clipped, masked and composited using the various painting, filtering, clipping, masking and object opacity settings on the given child. Any filter effects, masking and group opacity that might be set on A_i do not apply when rendering the children of A_i into BUF_i.
  
  (Note that for the case of A₀=E, the graphical contents of E are not rendered into BUF₁ and thus are not part of the background image available to E. Instead, the graphical contents of E are available via the SourceGraphic and SourceAlpha pseudo input images.)
• Then, for each A_i (from i=1 to n-1), composite BUF_i into BUF_i+1.
• The accumulated result (i.e., BUF_n) represents the background image available to E.

Example: enable-background-01.svg

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="13.5cm" height="2.7cm" viewBox="0 0 1350 270"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <title>Example enable-background01</title>
  <desc>This test case shows five pictures which illustrate the rules
        for background image processing.</desc>

  <defs>
    <filter id="ShiftBGAndBlur" 
            filterUnits="userSpaceOnUse" x="0" y="0" width="1200" height="400">
      <desc>
        This filter discards the SourceGraphic, if any, and just produces
        a result consisting of the BackgroundImage shifted down 125 units
        and then blurred.
      </desc>
      <feOffset in="BackgroundImage" dx="0" dy="125" />
      <feGaussianBlur stdDeviation="8" />
    </filter>
    <filter id="ShiftBGAndBlur_WithSourceGraphic" 
            filterUnits="userSpaceOnUse" x="0" y="0" width="1200" height="400">
      <desc>
        This filter takes the BackgroundImage, shifts it down 125 units, blurs it,
        and then renders the SourceGraphic on top of the shifted/blurred background.
      </desc>
      <feOffset in="BackgroundImage" dx="0" dy="125" />
      <feGaussianBlur stdDeviation="8" result="blur" />
      <feMerge>
        <feMergeNode in="blur"/>
        <feMergeNode in="SourceGraphic"/>
      </feMerge>
    </filter>
  </defs>

  <g transform="translate(0,0)">
    <desc>The first picture is our reference graphic without filters.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>

  <g enable-background="new" transform="translate(270,0)">
    <desc>The second adds an empty 'g' element which invokes ShiftBGAndBlur.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"/>
    </g>
    <g filter="url(#ShiftBGAndBlur)"/>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>

  <g enable-background="new" transform="translate(540,0)">
    <desc>The third invokes ShiftBGAndBlur on the inner group.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g filter="url(#ShiftBGAndBlur)" opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>

  <g enable-background="new" transform="translate(810,0)">
    <desc>The fourth invokes ShiftBGAndBlur on the triangle.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"
               filter="url(#ShiftBGAndBlur)"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>

  <g enable-background="new" transform="translate(1080,0)">
    <desc>The fifth invokes ShiftBGAndBlur_WithSourceGraphic on the triangle.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"
               filter="url(#ShiftBGAndBlur_WithSourceGraphic)"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>
</svg>

    

The example above contains five parts, described as follows:

1. The first set is the reference graphic. The reference graphic consists of a red rectangle followed by a 50% transparent 'g' element. Inside the 'g' is a green circle that partially overlaps the rectangle and a a blue triangle that partially overlaps the circle. The three objects are then outlined by a rectangle stroked with a thin blue line. No filters are applied to the reference graphic.
2. The second set enables background image processing and adds an empty 'g' element which invokes the ShiftBGAndBlur filter. This filter takes the current accumulated background image (i.e., the entire reference graphic) as input, shifts its offscreen down, blurs it, and then writes the result to the canvas. Note that the offscreen for the filter is initialized to transparent black, which allows the already rendered rectangle, circle and triangle to show through after the filter renders its own result to the canvas.
3. The third set enables background image processing and instead invokes the ShiftBGAndBlur filter on the inner 'g' element. The accumulated background at the time the filter is applied contains only the red rectangle. Because the children of the inner 'g' (i.e., the circle and triangle) are not part of the inner 'g' element's background and because ShiftBGAndBlur ignores SourceGraphic, the children of the inner 'g' do not appear in the result.
4. The fourth set enables background image processing and invokes the ShiftBGAndBlur on the 'polygon' element that draws the triangle. The accumulated background at the time the filter is applied contains the red rectangle plus the green circle ignoring the effect of the 'opacity' property on the inner 'g' element. (Note that the blurred green circle at the bottom does not let the red rectangle show through on its left side. This is due to ignoring the effect of the 'opacity' property.) Because the triangle itself is not part of the accumulated background and because ShiftBGAndBlur ignores SourceGraphic, the triangle does not appear in the result.
5. The fifth set is the same as the fourth except that filter ShiftBGAndBlur_WithSourceGraphic is invoked instead of ShiftBGAndBlur. ShiftBGAndBlur_WithSourceGraphic performs the same effect as ShiftBGAndBlur, but then renders the SourceGraphic on top of the shifted, blurred background image. In this case, SourceGraphic is the blue triangle; thus, the result is the same as in the fourth case except that the blue triangle now appears.

6 Filter primitives overview

6.1 Overview

This section describes the various filter primtives that can be assembled to achieve a particular filter effect.

Unless otherwise stated, all image filters operate on premultiplied RGBA samples. Filters which work more naturally on non-premultiplied data (feColorMatrix and feComponentTransfer) will temporarily undo and redo premultiplication as specified. All raster effect filtering operations take 1 to N input RGBA images, additional attributes as parameters, and produce a single output RGBA image.

The RGBA result from each filter primitive will be clamped into the allowable ranges for colors and opacity values. Thus, for example, the result from a given filter primitive will have any negative color values or opacity values adjusted up to color/opacity of zero.

The color space in which a particular filter primitive performs its operations is determined by the value of property 'color-interpolation-filters' on the given filter primitive. A different property, 'color-interpolation' determines the color space for other color operations. Because these two properties have different initial values ('color-interpolation-filters' has an initial value of linearRGB whereas 'color-interpolation' has an initial value of sRGB), in some cases to achieve certain results (e.g., when coordinating gradient interpolation with a filtering operation) it will be necessary to explicitly set 'color-interpolation' to linearRGB or 'color-interpolation-filters' to sRGB on particular elements. Note that the examples below do not explicitly set either 'color-interpolation' or 'color-interpolation-filters', so the initial values for these properties apply to the examples.

6.2 Common attributes

The following attributes are available for most of the filter primitives:

6.3 Filter primitive subregion

x, y, width and height default to the union (i.e., tightest fitting bounding box) of the subregions defined for all referenced nodes. If there are no referenced nodes (e.g., for 'feImage' or 'feTurbulence'), or one or more of the referenced nodes is a standard input (one of SourceGraphic, SourceAlpha, BackgroundImage, BackgroundAlpha, FillPaint or StrokePaint), or for 'feTile' (which is special because its principal function is to replicate the referenced node in X and Y and thereby produce a usually larger result), the default subregion is 0%,0%,100%,100%, where percentages are relative to the dimensions of the filter region.

Example: filtersubregion00.svg

<svg width="400" height="400" xmlns="http://www.w3.org/2000/svg"> 
	<defs>
		<filter id="flood" x="0" y="0" width="100%" height="100%" primitiveUnits="objectBoundingBox">
		   <feFlood x="25%" y="25%" width="50%" height="50%"
					flood-color="green" flood-opacity="0.75"/>
		</filter>
		<filter id="blend" primitiveUnits="objectBoundingBox">
		   <feBlend x="25%" y="25%" width="50%" height="50%"
					in2="SourceGraphic" mode="multiply"/>
		</filter>
		<filter id="merge" primitiveUnits="objectBoundingBox">
		   <feMerge x="25%" y="25%" width="50%" height="50%">
				<feMergeNode in="SourceGraphic"/>
				<feMergeNode in="FillPaint"/>
		   </feMerge>
		</filter>
	</defs>
	
	<g fill="none" stroke="blue" stroke-width="4">
	   <rect width="200" height="200"/>
	   <line x2="200" y2="200"/>
	   <line x1="200" y2="200"/>
	</g>
	<circle fill="green" filter="url(#flood)" cx="100" cy="100" r="90"/>

	<g transform="translate(200 0)">
		<g fill="none" stroke="blue" stroke-width="4">
		   <rect width="200" height="200"/>
		   <line x2="200" y2="200"/>
		   <line x1="200" y2="200"/>
		</g>
		<circle fill="green" filter="url(#blend)" cx="100" cy="100" r="90"/>
	</g>
	
	<g transform="translate(0 200)">
		<g fill="none" stroke="blue" stroke-width="4">
		   <rect width="200" height="200"/>
		   <line x2="200" y2="200"/>
		   <line x1="200" y2="200"/>
		</g>
		<circle fill="green" fill-opacity="0.5" filter="url(#merge)" cx="100" cy="100" r="90"/>
	</g>
</svg>    

In the example above there are three rects that each have a cross and a circle in them. The circle element in each one has a different filter applied, but with the same filter primitive subregion. The filter output should be limited to the filter primitive subregion, so you should never see the circles themselves, just the rects that make up the filter primitive subregion.

• The upper left rect shows an 'feFlood' with flood-opacity="75%" so the cross should be visible through the green rect in the middle.
• The lower left rect shows an 'feMerge' that merges SourceGraphic with FillPaint. Since the circle has fill-opacity="0.5" it will also be transparent so that the cross is visible through the green rect in the middle.
• The upper right rect shows an 'feBlend' that has mode="multiply". Since the circle in this case isn't transparent the result is totally opaque. The rect should be dark green and the cross should not be visible through it.

7 Light source elements and properties

7.1 Introduction

The following sections define the elements that define a light source, 'feDistantLight', 'fePointLight' and 'feSpotLight', and property 'lighting-color', which defines the color of the light.

7.2 Light source 'feDistantLight'

7.3 Light source 'fePointLight'

7.4 Light source 'feSpotLight'

7.5 The 'lighting-color' property

The 'lighting-color' property defines the color of the light source for filter primitives 'feDiffuseLighting' and 'feSpecularLighting'.

8 Filter primitive 'feBlend'

This filter composites two objects together using commonly used imaging software blending modes. It performs a pixel-wise combination of two input images.

For all feBlend modes, the result opacity is computed as follows:

qr = 1 - (1-qa)*(1-qb)

For the compositing formulas below, the following definitions apply:

image A = in
image B = in2
cr = Result color (RGB) - premultiplied 
qa = Opacity value at a given pixel for image A 
qb = Opacity value at a given pixel for image B 
ca = Color (RGB) at a given pixel for image A - premultiplied 
cb = Color (RGB) at a given pixel for image B - premultiplied 

The following table provides the list of available image blending modes:

'normal' blend mode is equivalent to operator="over" on the 'feComposite' filter primitive, matches the blending method used by 'feMerge' and matches the simple alpha compositing technique used in SVG for all compositing outside of filter effects.

Example: feBlend.svg

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="5cm" height="5cm" viewBox="0 0 500 500"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <title>Example feBlend - Examples of feBlend modes</title>
  <desc>Five text strings blended into a gradient,
        with one text string for each of the five feBlend modes.</desc>
  <defs>
    <linearGradient id="MyGradient" gradientUnits="userSpaceOnUse"
            x1="100" y1="0" x2="300" y2="0">
      <stop offset="0" stop-color="#000000" />
      <stop offset=".33" stop-color="#ffffff" />
      <stop offset=".67" stop-color="#ff0000" />
      <stop offset="1" stop-color="#808080" />
    </linearGradient>
    <filter id="Normal">
      <feBlend mode="normal" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Multiply">
      <feBlend mode="multiply" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Screen">
      <feBlend mode="screen" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Darken">
      <feBlend mode="darken" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Lighten">
      <feBlend mode="lighten" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
  </defs>
  <rect fill="none" stroke="blue"  
        x="1" y="1" width="498" height="498"/>
  <g enable-background="new" >
    <rect x="100" y="20" width="300" height="460" fill="url(#MyGradient)" />
    <g font-family="Verdana" font-size="75" fill="#888888" fill-opacity=".6" >
      <text x="50" y="90" filter="url(#Normal)" >Normal</text>
      <text x="50" y="180" filter="url(#Multiply)" >Multiply</text>
      <text x="50" y="270" filter="url(#Screen)" >Screen</text>
      <text x="50" y="360" filter="url(#Darken)" >Darken</text>
      <text x="50" y="450" filter="url(#Lighten)" >Lighten</text>
    </g>
  </g>
</svg>

    

9 Filter primitive 'feColorMatrix'

This filter applies a matrix transformation:

| R' |     | a00 a01 a02 a03 a04 |   | R |
| G' |     | a10 a11 a12 a13 a14 |   | G |
| B' |  =  | a20 a21 a22 a23 a24 | * | B |
| A' |     | a30 a31 a32 a33 a34 |   | A |
| 1  |     |  0   0   0   0   1  |   | 1 |

on the RGBA color and alpha values of every pixel on the input graphics to produce a result with a new set of RGBA color and alpha values.

The calculations are performed on non-premultiplied color values. If the input graphics consists of premultiplied color values, those values are automatically converted into non-premultiplied color values for this operation.

These matrices often perform an identity mapping in the alpha channel. If that is the case, an implementation can avoid the costly undoing and redoing of the premultiplication for all pixels with A = 1.

Example: feColorMatrix.svg

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="8cm" height="5cm" viewBox="0 0 800 500"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <title>Example feColorMatrix - Examples of feColorMatrix operations</title>
  <desc>Five text strings showing the effects of feColorMatrix: 
        an unfiltered text string acting as a reference, 
        use of the feColorMatrix matrix option to convert to grayscale,
        use of the feColorMatrix saturate option,
        use of the feColorMatrix hueRotate option,
        and use of the feColorMatrix luminanceToAlpha option.</desc>
  <defs>
    <linearGradient id="MyGradient" gradientUnits="userSpaceOnUse"
            x1="100" y1="0" x2="500" y2="0">
      <stop offset="0" stop-color="#ff00ff" />
      <stop offset=".33" stop-color="#88ff88" />
      <stop offset=".67" stop-color="#2020ff" />
      <stop offset="1" stop-color="#d00000" />
    </linearGradient>
    <filter id="Matrix" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="matrix" in="SourceGraphic"
           values=".33 .33 .33 0 0 
                   .33 .33 .33 0 0 
                   .33 .33 .33 0 0 
                   .33 .33 .33 0 0"/>
    </filter>
    <filter id="Saturate40" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="saturate" in="SourceGraphic" values="40%"/>
    </filter>
    <filter id="HueRotate90" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="hueRotate" in="SourceGraphic" values="90"/>
    </filter>
    <filter id="LuminanceToAlpha" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="luminanceToAlpha" in="SourceGraphic" result="a"/>
      <feComposite in="SourceGraphic" in2="a" operator="in" />
    </filter>
  </defs>
  <rect fill="none" stroke="blue"  
        x="1" y="1" width="798" height="498"/>
  <g font-family="Verdana" font-size="75" 
            font-weight="bold" fill="url(#MyGradient)" >
    <rect x="100" y="0" width="500" height="20" />
    <text x="100" y="90">Unfiltered</text>
    <text x="100" y="190" filter="url(#Matrix)" >Matrix</text>
    <text x="100" y="290" filter="url(#Saturate40)" >Saturate</text>
    <text x="100" y="390" filter="url(#HueRotate90)" >HueRotate</text>
    <text x="100" y="490" filter="url(#LuminanceToAlpha)" >Luminance</text>
  </g>
</svg>

    

10 Filter primitive 'feComponentTransfer'

This filter primitive performs component-wise remapping of data as follows:

R' = feFuncR( R )
G' = feFuncG( G )
B' = feFuncB( B )
A' = feFuncA( A )

for every pixel. It allows operations like brightness adjustment, contrast adjustment, color balance or thresholding.

The calculations are performed on non-premultiplied color values. If the input graphics consists of premultiplied color values, those values are automatically converted into non-premultiplied color values for this operation. (Note that the undoing and redoing of the premultiplication can be avoided if feFuncA is the identity transform and all alpha values on the source graphic are set to 1.)

The specification of the transfer functions is defined by the sub-elements to 'feComponentTransfer':

'feFuncR', transfer function for red component of the input graphic

'feFuncG', transfer function for green component of the input graphic

'feFuncB', transfer function for blue component of the input graphic

'feFuncA', transfer function for alpha component of the input graphic

The attributes below apply to sub-elements 'feFuncR', 'feFuncG', 'feFuncB' and 'feFuncA' define the transfer functions.

Example: feComponentTransfer.svg

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="8cm" height="4cm" viewBox="0 0 800 400"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <title>Example feComponentTransfer - Examples of feComponentTransfer operations</title>
  <desc>Four text strings showing the effects of feComponentTransfer: 
        an identity function acting as a reference, 
        use of the feComponentTransfer table option,
        use of the feComponentTransfer linear option,
        and use of the feComponentTransfer gamma option.</desc>
  <defs>
    <linearGradient id="MyGradient" gradientUnits="userSpaceOnUse"
            x1="100" y1="0" x2="600" y2="0">
      <stop offset="0" stop-color="#ff0000" />
      <stop offset=".33" stop-color="#00ff00" />
      <stop offset=".67" stop-color="#0000ff" />
      <stop offset="1" stop-color="#000000" />
    </linearGradient>
    <filter id="Identity" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="identity"/>
        <feFuncG type="identity"/>
        <feFuncB type="identity"/>
        <feFuncA type="identity"/>
      </feComponentTransfer>
    </filter>
    <filter id="Table" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="table" tableValues="0 0 1 1"/>
        <feFuncG type="table" tableValues="1 1 0 0"/>
        <feFuncB type="table" tableValues="0 1 1 0"/>
      </feComponentTransfer>
    </filter>
    <filter id="Linear" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="linear" slope=".5" intercept=".25"/>
        <feFuncG type="linear" slope=".5" intercept="0"/>
        <feFuncB type="linear" slope=".5" intercept=".5"/>
      </feComponentTransfer>
    </filter>
    <filter id="Gamma" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="gamma" amplitude="2" exponent="5" offset="0"/>
        <feFuncG type="gamma" amplitude="2" exponent="3" offset="0"/>
        <feFuncB type="gamma" amplitude="2" exponent="1" offset="0"/>
      </feComponentTransfer>
    </filter>
  </defs>
  <rect fill="none" stroke="blue"  
        x="1" y="1" width="798" height="398"/>
  <g font-family="Verdana" font-size="75" 
            font-weight="bold" fill="url(#MyGradient)" >
    <rect x="100" y="0" width="600" height="20" />
    <text x="100" y="90">Identity</text>
    <text x="100" y="190" filter="url(#Table)" >TableLookup</text>
    <text x="100" y="290" filter="url(#Linear)" >LinearFunc</text>
    <text x="100" y="390" filter="url(#Gamma)" >GammaFunc</text>
  </g>
</svg>

    

11 Filter primitive 'feComposite'

This filter performs the combination of the two input images pixel-wise in image space using one of the Porter-Duff [PORTERDUFF] compositing operations: over, in, atop, out, xor. Additionally, a component-wise arithmetic operation (with the result clamped between [0..1]) can be applied.

The arithmetic operation is useful for combining the output from the 'feDiffuseLighting' and 'feSpecularLighting' filters with texture data. It is also useful for implementing dissolve. If the arithmetic operation is chosen, each result pixel is computed using the following formula:

result = k1*i1*i2 + k2*i1 + k3*i2 + k4

For this filter primitive, the extent of the resulting image might grow as described in the section that describes the filter primitive subregion.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="330" height="195" viewBox="0 0 1100 650" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <title>Example feComposite - Examples of feComposite operations</title>
  <desc>Four rows of six pairs of overlapping triangles depicting
        the six different feComposite operators under different
        opacity values and different clearing of the background.</desc>
	<defs>
    <desc>Define two sets of six filters for each of the six compositing operators.
          The first set wipes out the background image by flooding with opaque white.
          The second set does not wipe out the background, with the result
          that the background sometimes shines through and is other cases
          is blended into itself (i.e., "double-counting").</desc>
    <filter id="overFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="over" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="inFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="in" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="outFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="out" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="atopFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="atop" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="xorFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="xor" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="arithmeticFlood" filterUnits="objectBoundingBox" 
            x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" result="comp"
                   operator="arithmetic" k1=".5" k2=".5" k3=".5" k4=".5"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="overNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="over" result="comp"/>
    </filter>
    <filter id="inNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="in" result="comp"/>
    </filter>
    <filter id="outNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="out" result="comp"/>
    </filter>
    <filter id="atopNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="atop" result="comp"/>
    </filter>
    <filter id="xorNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="xor" result="comp"/>
    </filter>
    <filter id="arithmeticNoFlood" filterUnits="objectBoundingBox" 
            x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" result="comp"
                   operator="arithmetic" k1=".5" k2=".5" k3=".5" k4=".5"/>
    </filter>
    <path id="Blue100" d="M 0 0 L 100 0 L 100 100 z" fill="#00ffff" />
    <path id="Red100" d="M 0 0 L 0 100 L 100 0 z" fill="#ff00ff" />
    <path id="Blue50" d="M 0 125 L 100 125 L 100 225 z" fill="#00ffff" fill-opacity=".5" />
    <path id="Red50" d="M 0 125 L 0 225 L 100 125 z" fill="#ff00ff" fill-opacity=".5" />
    <g id="TwoBlueTriangles">
      <use xlink:href="#Blue100"/>
      <use xlink:href="#Blue50"/>
    </g>
    <g id="BlueTriangles">
      <use transform="translate(275,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(400,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(525,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(650,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(775,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(900,25)" xlink:href="#TwoBlueTriangles"/>
    </g>
  </defs>

  <