filter

This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for the proper prefixes to use in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the spec changes.

Summary

The CSS filter property provides for effects like blurring or color shifting on an element’s rendering before the element is displayed. Filters are commonly used to adjust the rendering of an image, a background, or a border.

Included in the CSS standard are several functions that achieve predefined effects. You can also reference a filter specified in SVG with a URL to an SVG filter element.

Note: Older versions (4.0 through 9.0) of the Windows Internet Explorer browser supported a non-standard "filter" that has since been deprecated.

Syntax

With a function, use the following:

filter: <filter-function> [<filter-function>]* | none

For a reference to an SVG <filter> element, use the following:

filter: url(svg-url#element-id)

Examples

Examples of using the predefined functions are shown below. See each function for a specific example.

.mydiv { filter: grayscale(50%) }

/* gray all images by 50% and blur by 10px */
img {
  filter: grayscale(0.5) blur(10px);
}

Examples of using the URL function with an SVG resource are shown below.

.target { filter: url(#c1); }

.mydiv { filter: url(commonfilters.xml#large-blur) }

Functions

To use the CSS filter property, you specify a value for one of the following functions. If the value is invalid, the function returns "none." Except where noted, the functions that take a value expressed with a percent sign (as in 34%) also accept the value expressed as decimal (as in 0.34).

url()

The url() function takes the location of an XML file that specifies an SVG filter, and may include an anchor to a specific filter element.

filter: url(resources.svg#c1)

blur()

Applies a Gaussian blur to the input image. The value of ‘radius’ defines the value of the standard deviation to the Gaussian function, or how many pixels on the screen blend into each other, so a larger value will create more blur. If no parameter is provided, then a value 0 is used. The parameter is specified as a CSS length, but does not accept percentage values.

filter: blur(5px)

<svg height="0" xmlns="http://www.w3.org/2000/svg">
  <filter id="svgBlur" x="-5%" y="-5%" width="110%" height="110%">
    <feGaussianBlur in="SourceGraphic" stdDeviation="5"/>
  </filter>
</svg>

brightness()

Applies a linear multiplier to input image, making it appear more or less bright. A value of 0% will create an image that is completely black. A value of 100% leaves the input unchanged. Other values are linear multipliers on the effect. Values of an amount over 100% are allowed, providing brighter results. If the ‘amount’ parameter is missing, a value of 100% is used.

filter: brightness(0.5)
<svg height="0" xmlns="http://www.w3.org/2000/svg">
 <filter id="brightness">
    <feComponentTransfer>
        <feFuncR type="linear" slope="[amount]"/>
        <feFuncG type="linear" slope="[amount]"/>
        <feFuncB type="linear" slope="[amount]"/>
    </feComponentTransfer>
  </filter>
</svg>

contrast()

Adjusts the contrast of the input. A value of 0% will create an image that is completely black. A value of 100% leaves the input unchanged. Values of amount over 100% are allowed, providing results with less contrast. If the ‘amount’ parameter is missing, a value of 100% is used.

filter: contrast(200%)

<svg height="0" xmlns="http://www.w3.org/2000/svg">
  <filter id="contrast">
    <feComponentTransfer>
      <feFuncR type="linear" slope="[amount]" intercept="-(0.5 * [amount]) + 0.5"/>
      <feFuncG type="linear" slope="[amount]" intercept="-(0.5 * [amount]) + 0.5"/>
      <feFuncB type="linear" slope="[amount]" intercept="-(0.5 * [amount]) + 0.5"/>
    </feComponentTransfer>
  </filter>
</svg>

drop-shadow()

Applies a drop shadow effect to the input image. A drop shadow is effectively a blurred, offset version of the input image's alpha mask drawn in a particular color, composited below the image. The function accepts a parameter of type <shadow> (defined in CSS3 Backgrounds), with the exception that the ‘inset’ keyword is not allowed. This function is similar to the more established box-shadow property; the difference is that with filters, some browsers provide hardware acceleration for better performance. The parameters of the <shadow> property are as follows.

<offset-x> <offset-y> (required)
This are two <length> values to set the shadow offset. <offset-x> specifies the horizontal distance. Negative values place the shadow to the left of the element. <offset-y> specifies the vertical distance. Negative values place the shadow above the element. See <length> for possible units.
If both values are 0, the shadow is placed behind the element (and may generate a blur effect if <blur-radius> and/or <spread-radius> is set).
<blur-radius> (optional)
This is a third <length> value. The larger this value, the bigger the blur, so the shadow becomes bigger and lighter. Negative values are not allowed. If not specified, it will be 0 (the shadow's edge is sharp).
<spread-radius> (optional)
This is a fourth <length> value. Positive values will cause the shadow to expand and grow bigger, negative values will cause the shadow to shrink. If not specified, it will be 0 (the shadow will be the same size as the element). 
Note: Webkit, and maybe other browsers, do not support this 4th length, it will not render if added.
 
<color> (optional)
See <color> values for possible keywords and notations.
If not specified, the color depends on the browser. In Gecko (Firefox), Presto (Opera) and Trident (Internet Explorer), the value of the color property is used. On the other hand, WebKit's shadow is transparent and therefore useless if <color> is omitted.
filter: drop-shadow(16px 16px 10px black)
<svg height="0" xmlns="http://www.w3.org/2000/svg">
 <filter id="drop-shadow">
    <feGaussianBlur in="SourceAlpha" stdDeviation="[radius]"/>
    <feOffset dx="[offset-x]" dy="[offset-y]" result="offsetblur"/>
    <feFlood flood-color="[color]"/>
    <feComposite in2="offsetblur" operator="in"/>
    <feMerge>
      <feMergeNode/>
      <feMergeNode in="SourceGraphic"/>
    </feMerge>
  </filter>
</svg>

grayscale()

Converts the input image to grayscale. The value of ‘amount’ defines the proportion of the conversion. A value of 100% is completely grayscale. A value of 0% leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. If the ‘amount’ parameter is missing, a value of 100% is used.

filter: grayscale(100%)

hue-rotate()

Applies a hue rotation on the input image. The value of ‘angle’ defines the number of degrees around the color circle the input samples will be adjusted. A value of 0deg leaves the input unchanged. If the ‘angle’ parameter is missing, a value of 0deg is used. Maximum value is 360deg.

filter: hue-rotate(90deg)

invert()

Inverts the samples in the input image. The value of ‘amount’ defines the proportion of the conversion. A value of 100% is completely inverted. A value of 0% leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. If the ‘amount’ parameter is missing, a value of 100% is used.

filter: invert(100%)

opacity()

Applies transparency to the samples in the input image. The value of ‘amount’ defines the proportion of the conversion. A value of 0% is completely transparent. A value of 100% leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. This is equivalent to multiplying the input image samples by amount. If the ‘amount’ parameter is missing, a value of 100% is used. This function is similar to the more established opacity property; the difference is that with filters, some browsers provide hardware acceleration for better performance.

filter: opacity(50%)

saturate()

Saturates the input image. The value of ‘amount’ defines the proportion of the conversion. A value of 0% is completely un-saturated. A value of 100% leaves the input unchanged. Other values are linear multipliers on the effect. Values of amount over 100% are allowed, providing super-saturated results. If the ‘amount’ parameter is missing, a value of 100% is used.

filter: saturate(200%)

sepia()

Converts the input image to sepia. The value of ‘amount’ defines the proportion of the conversion. A value of 100% is completely sepia. A value of 0 leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. If the ‘amount’ parameter is missing, a value of 100% is used.

filter: sepia(100%)

Combining functions

You may combine any number of functions to manipulate the rendering. The following example enhances the contrast and brightness of the image.

filter: contrast(175%) brightness(3%)

Specifications

Specification Status Comment
Filter Effects 1.0 Working Draft Initial definition.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 18.0-webkit Not supported
 (see note)		 Not supported (see note) 17.0 -webkit (Yes)-webkit
Feature Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? ? ? ?

?

Gecko notes

Gecko currently only implements the url() form of the filter property.

Internet Explorer notes

Internet Explorer 4.0 to 9.0 implemented a non-standard filter property. The syntax was completely different from this one and is not documented here.

Chrome notes

In Chrome 18 to 19, saturate() function only takes integers instead of decimal or percentage values. This bug is fixed in Chrome 20 and further.

See also

Attachments

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