# brightness

> Applies a `filter: brightness(...)`, scaling every pixel's lightness.

```ts
import { brightness } from "@sdxc/u/effects";
```

Applies a `filter: brightness(...)`, scaling every pixel's lightness. Values
below `1` darken and above `1` brighten; `0` is solid black. Composes with
every other filter utility through the shared composite `filter`.

## Quick reference

Every documented call, beside the CSS it emits.

| Call | CSS |
| --- | --- |
| `u.brightness(1.1)` | `css({ "--ui-filter-brightness": "1.1", filter: "blur(var(--ui-filter-blur, 0px)) brightness(var(--ui-filter-brightness, 1)) ..." })` |

## Examples

### Basic example

Use `brightness(n)` to scale an element's lightness, where values below `1` darken it and values above `1` brighten it:

```tsx
<div mix={[...]}>
	<div mix={[...]}>
		<img mix={[brightness(0.5), ...]} src={...} alt="" />
		<span mix={[...]}>brightness(0.5)</span>
	</div>
	<div mix={[...]}>
		<img mix={[brightness(1), ...]} src={...} alt="" />
		<span mix={[...]}>brightness(1)</span>
	</div>
	<div mix={[...]}>
		<img mix={[brightness(1.5), ...]} src={...} alt="" />
		<span mix={[...]}>brightness(1.5)</span>
	</div>
</div>
```

### Brightening on hover

Combine it with `hover()` and `transition()` to light up a clickable image. Hover the photograph:

```tsx
<a href="/gallery/landscape">
	<img
		mix={[hover(brightness(1.25)), transition("filter"), ...]}
		src={...}
		alt="Landscape"
	/>
</a>
```

## Using a custom value

Every scale argument also takes a raw CSS value, which passes through untouched.

```ts
u.brightness("2.75rem")
```

## Applying on a state

Wrap the call in a state utility to scope it to one selector.

```ts
u.hover(u.brightness(1.1))
```

## Responsive design

Wrap the call in a container query to scope it to one width.

```ts
u.at("md", u.brightness(1.1))
```

## Signature

```ts
u.brightness(value?: number | (string & {}))
```