我們的志工尚未將此文章翻譯為 正體中文 (繁體) 版本。加入我們，幫忙翻譯！
<circle> this attribute defines the radius of the element. A value of zero disables rendering of the circle.
<radialgradient> element, this attribute defines the radius of the largest (i.e., outermost) circle for the radial gradient. The gradient will be drawn such that the 100% gradient stop is mapped to the perimeter of this largest (i.e., outermost) circle. A value of zero will cause the area to be painted as a single color using the color and opacity of the last gradient
<stop>. If the attribute is not specified, the effect is as if a value of 50% were specified.
|Normative document||SVG 1.1 (2nd Edition): The circle element |
SVG 1.1 (2nd Edition): The radialGradient element
A length is a distance measurement, given as a number along with a unit. Lengths are specified in one of two ways. When used in a stylesheet, a <length> is defined as follows:
length ::= number (~"em" | ~"ex" | ~"px" | ~"in" | ~"cm" | ~"mm" | ~"pt" | ~"pc")?
See the CSS2 specification for the meanings of the unit identifiers.
For properties defined in CSS2, a length unit identifier must be provided. For length values in SVG-specific properties and their corresponding presentation attributes, the length unit identifier is optional. If not provided, the length value represents a distance in the current user coordinate system. In presentation attributes for all properties, whether defined in SVG1.1 or in CSS2, the length identifier, if specified, must be in lower case.
When lengths are used in an SVG attribute, a <length> is instead defined as follows:
length ::= number ("em" | "ex" | "px" | "in" | "cm" | "mm" | "pt" | "pc" | "%")?
The unit identifiers in such <length> values must be in lower case.
Note that the non-property <length> definition also allows a percentage unit identifier. The meaning of a percentage length value depends on the attribute for which the percentage length value has been specified. Two common cases are:
- when a percentage length value represents a percentage of the viewport width or height
- when a percentage length value represents a percentage of the bounding box width or height on a given object.
The following code snippet demonstrates the "r" attribute of the <circle> element.
<?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 xmlns="http://www.w3.org/2000/svg" version="1.1"> <circle cx="200" cy="150" r="50" stroke-width="1" fill="blue" /> </svg>
The following elements can use the