CSS Filters are a powerful tool that authors can use to achieve varying and visual effects (sort of like Photoshop filters for the browser). The CSS filter property provides tools to effects like blur 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.
The syntax is:
Where is one of:
- blur()
- brightness()
- contrast()
- drop-shadow()
- grayscale()
- hue-rotate()
- invert()
- opacity()
- saturate()
- sepia()
- url() – for applying SVG filters
- custom() – “coming soon”
Multiple functions can be used, space is separated.
Example of a single filter is used:
Example of multiple filters is used:
Filter Functions
To use the CSS filter property, you specify a value for one of the following functions listed above. If the value is invalid, the function will return “none.” Except where noted, the functions that take a value expressed with a percent sign (as in 34%) also accept the value expressed by decimal (as in 0.34).
Below we’ll use a variety of different filter functions on this image:
grayscale()
Convert 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 being missed, a value of 100% will be used. Negative values are not allowed.
Example
Result
sepia()
Convert 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 being missed, a value of 100% is used. Negative values are not allowed.
Example
Result
saturate()
Saturate 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 being missed, a value of 100% will be used. Negative values are not allowed.
Example
Result
hue-rotate()
Apply 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 being missed, a value of 0deg will be used. Maximum value is 360deg.
Example
Result
invert()
Invert 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 being missed, a value of 100% will be used. Negative values are not allowed.
Example
Result
opacity()
Apply 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 being missed, a value of 100% will be 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. Negative values are not allowed.
Example
Result
brightness()
Apply 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 being missed, a value of 100% will be used.
Example
Result
contrast()
Adjust 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.
Example
Result
blur()
Apply 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.
Example
Result
drop-shadow()
Apply 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 (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.
Example
Result
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.
Example
Notes
You may combine any number of functions to manipulate the rendering, but order still matters (i.e., using grayscale() after sepia() will result in completely gray output).
A computed value of other than “none” results in the creation of a stacking context the same way that CSS opacity does. The filter property has no effect on the geometry of the target element’s box model, even though filters can cause painting outside of an element’s border box. Any parts of the target element are affected by filter functions. This includes any content, background, borders, text decoration, outline and visible scrolling mechanism of the element to which the filter is applied, and those of its descendants. Filters can also be applied to inline content, such as individual text spans.
The specification also introduces a filter(image-URL, filter-functions) wrapper function for an image. It will allow you to filter any image at the time you use it within CSS. For example, you could blur a background image without blurring the text. This filter function is not yet supported in browsers. In the meantime, you can apply both the background and the filter to a pseudo-element to create a similar effect.
The IE proprietary filter stuff
Also used the filter property, like:
Mostly used for opacity when you need to support IE 8 and down.