Alpha channel
An alpha channel is a color or image component that specifies the opacity or transparency of each color or pixel.
Web Design Playground, Second Edition
An alpha channel is a color component that specifies the degree of transparency or opacity.
- How it is used
- Controls text and color transparency when designing CSS effects while preserving enough readability for the page.
- How deep it goes
- Defines decimal and hexadecimal alpha ranges with examples, but stops short of deeper compositing behavior.
- Examples
- Uses partially transparent text and #rrggbbaa notation, including 00 and ff hexadecimal endpoints.
- What you can do after
- Apply it via CSS color functions and hexadecimal codes to make text or colors partly transparent.
Read how Web Design Playground, Second Edition explains alpha channel →
Math for Web Design
Alpha is a graphics channel value from zero to one that represents a color's opacity or coverage during compositing.
- How it is used
- Specifies transparency in CSS colors and supplies the weighting used when foreground and background colors are composited.
- How deep it goes
- Defines alpha ranges and notation, then derives source-over compositing per channel with a worked example.
- Examples
- Uses semitransparent purple and blue-over-red examples across rgb(), hexadecimal, and lab() color notation.
- What you can do after
- Apply alpha through CSS rgb(), hexadecimal, or lab() notation and predict the resulting color over an opaque background.
Get Programming with JavaScript Next: New features of ECMAScript 2015, 2016, and beyond
The transparency component of a color or image, typically represented as an opacity value from fully transparent to fully opaque.
- How it is used
- Uses alpha to fade images into a canvas gallery.
- How deep it goes
- Implements alpha-based redrawing with requestAnimationFrame and promise completion, without detailing rendering internals.
- Examples
- Demonstrates fading a gallery image from alpha 0.1 to 0.99.
- What you can do after
- Apply alpha to canvas images and signal fade completion with a promise.
Related concepts
- transparencyconfigures · Transparency is the degree to which underlying content is visible through an element or relevant information, processes, and decisions are accessible and understandable to observers.
- hexadecimal color notationconfigured by · Hexadecimal color notation is a textual representation of color components using hexadecimal digits, typically encoding red, green, blue, and optionally alpha.
- rgba()used by · The CSS rgba() function specifies a color using red, green, and blue components together with an alpha value controlling opacity.
- HSL methodused by · The HSL method represents colors using hue, saturation, and lightness within a color model or notation system.
- opacityconfigures · Opacity is the degree to which a rendered element or color appears solid rather than transparent.
- RGBA colorpart of · An RGBA color is a color representation specifying red, green, blue, and alpha channel values.
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