CSS不透明度プロパティ
例
<div>要素の不透明度レベルを設定します。
div
{
opacity: 0.5;
}
以下の「自分で試してみてください」の例をもっと見てください。
定義と使用法
このopacity
プロパティは、要素の不透明度レベルを設定します。
不透明度レベルは透明度レベルを表します。1はまったく透明ではなく、0.5は50%の透けて見え、0は完全に透明です。
Note: When using the opacity
property to add transparency to
the background of an element, all of its child elements become transparent as
well. This can make the text inside a fully transparent element hard to read. If
you do not want to apply opacity to child elements, use RGBA color values
instead (See "More Examples" below).
Default value: | 1 |
---|---|
Inherited: | no |
Animatable: | yes, see individual properties. Read about animatable |
Version: | CSS3 |
JavaScript syntax: | object.style.opacity="0.5" |
Browser Support
The numbers in the table specify the first browser version that fully supports the property.
Property | |||||
---|---|---|---|---|---|
opacity | 4.0 | 9.0 | 2.0 | 3.1 | 9.0 |
Note: IE8 and earlier versions supports an alternative, the filter property. Like: filter:Alpha(opacity=50).
CSS Syntax
opacity: number|initial|inherit;
Property Values
Value | Description | Play it |
---|---|---|
number | Specifies the opacity. From 0.0 (fully transparent) to 1.0 (fully opaque) | |
initial | Sets this property to its default value. Read about initial | |
inherit | Inherits this property from its parent element. Read about inherit |
More Examples
Example
The opacity property adds transparency to the background of an element, and to all of its child elements as well. This makes the text inside a transparent element hard to read:
div.first {
opacity: 0.1;
}
div.second {
opacity: 0.3;
}
div.third {
opacity: 0.6;
}
Example
To not apply opacity to child elements (like in the example above) use RGBA color values instead. The following example sets the opacity for the background color, but not for the text:
div.first {
background: rgba(76, 175, 80, 0.1);
}
div.second {
background: rgba(76, 175, 80, 0.3);
}
div.third {
background: rgba(76, 175, 80,
0.6);
}
Tip: Learn more about RGBA Colors in CSS RGBA Colors.
Example
How to use JavaScript to change the opacity for an element:
function myFunction(x) {
// Return the text of the selected option
var opacity = x.options[x.selectedIndex].text;
var el = document.getElementById("p1");
if (el.style.opacity !== undefined) {
el.style.opacity = opacity;
} else {
alert("Your browser doesn't support this example!");
}
}
Related Pages
CSS Tutorial: CSS Opacity / Transparency
CSS Tutorial: CSS RGBA Colors
HTML DOM Reference: opacity property