Web/CSS/shape-image-threshold

The shape-image-threshold CSS property sets the alpha channel threshold used to extract the shape using an image as the value for shape-outside.

Any pixels whose alpha component's value is greater than the threshold are considered to be part of the shape for the purposes of determining its boundaries. For example, a value of 0.5 means that the shape will enclose all the pixels that are more than 50% opaque.

Syntax

/* <number> value */
shape-image-threshold: 0.7;

/* Global values */
shape-image-threshold: inherit;
shape-image-threshold: initial;
shape-image-threshold: unset;

Values

<alpha-value>: Sets the threshold used for extracting a shape from an image. The shape is defined by the pixels whose alpha value is greater than the threshold. Values outside the range 0.0 (fully transparent) to 1.0 (fully opaque) are clamped to this range.

Formal definition

Initial value	`0.0`
Applies to	floats
Inherited	no
Computed value	The same as the specified value after clipping the `<number>` to the range [0.0, 1.0].
Animation type	a number

Formal syntax

<alpha-value>where <alpha-value> = <number> | <percentage>

Examples

Aligning text to a gradient

This example creates a <div> block with a gradient background image. The gradient is established as a CSS shape using shape-outside, so that pixels within the gradient which are at least 20% opaque (that is, those pixels with an alpha component greater than 0.2) are considered part of the shape.

HTML

<div id="gradient-shape"></div>

<p>
  Lorem ipsum dolor sit amet, consectetur adipisicing elit. Vel at commodi 
  voluptates enim, distinctio officia. Saepe optio accusamus doloribus sint 
  facilis itaque ab nulla, dolor molestiae assumenda cum sit placeat 
  adipisci, libero quae nihil porro debitis laboriosam inventore animi 
  impedit nostrum nesciunt quisquam expedita! Dolores consectetur iure atque 
  a mollitia dicta repudiandae illum exercitationem aliquam repellendus 
  ipsum porro modi, id nemo eligendi, architecto ratione quibusdam iusto 
  nisi soluta? Totam inventore ea eum sed velit et eligendi suscipit 
  accusamus iusto dolore, at provident eius alias maxime pariatur non 
  deleniti ipsum sequi rem eveniet laboriosam magni expedita?
</p>

CSS

#gradient-shape {
  width: 150px;
  height: 150px;
  float: left;
  background-image: linear-gradient(30deg, black, transparent 80%,
      transparent);
  shape-outside: linear-gradient(30deg, black, transparent 80%,
      transparent);
  shape-image-threshold: 0.2;
}

The shape is established here using background-image with a linear gradient rather than an image file. The same gradient is also used as the image from which the shape is derived for establishing the float area, using the shape-outside property.

The 20% opacity threshold for treating gradient pixels as part of the shape is then established using shape-image-threshold with a value of 0.2.

Result

Specifications

Specification	Status	Comment
CSS Shapes Module Level 1The definition of 'shape-image-threshold' in that specification.	Candidate Recommendation	Initial definition

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`shape-image-threshold`	Chrome Full support 37	Edge Full support 79	Firefox Full support 62 Full support 62 No support 61 — 62 Disabled' Disabled' From version 61 until version 62 (exclusive): this feature is behind the `layout.css.shape-outside.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera Full support 24	Safari Full support 10.1	WebView Android Full support 37	Chrome Android Full support 37	Firefox Android Full support 62 Full support 62 No support 61 — 62 Disabled' Disabled' From version 61 until version 62 (exclusive): this feature is behind the `layout.css.shape-outside.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android Full support 24	Safari iOS Full support 10.3	Samsung Internet Android Full support 3.0
Support for percentage opacity values	Chrome Full support 78	Edge Full support 79	Firefox Full support 70	IE No support No	Opera No support No	Safari No support No	WebView Android Full support 78	Chrome Android Full support 78	Firefox Android No support No	Opera Android No support No	Safari iOS No support No	Samsung Internet Android Full support 12.0

Legend

Full support: Full support
No support: No support
User must explicitly enable this feature.': User must explicitly enable this feature.