# Image Compare (Lumen Halo): prompt.md (v1.0.0)

- id: `lumen-image-compare` · version 1.0.0 · component · pro (Pro)
- category: Media & effects
- build: Base UI (one set of files; its dependencies follow the build)
- install (this build): `npx shadcn@latest add @beautiful-ui-pro/lumen-image-compare`
- npm dependencies: none
- registry dependencies: utils, https://beautiful-ui.dev/r/lumen-foundation.json
- docs: https://beautiful-ui.dev/components/lumen-image-compare
- The install command carries everything this item needs (files, CSS, tokens, npm and registry dependencies). Prefer it to copying source by hand.

Two images in one frame with a divider between them: drag anywhere or click to jump, or focus the handle and use the arrow keys. It's a slider, so it is named and says how much of each image shows.

## Build it
- Stack: React 19 (`ref` is a plain prop), TypeScript, Tailwind CSS v4 utilities, a shadcn-initialised project with the `@/*` alias.
- Packages: none beyond React.
- Files: `components/ui/lumen/controls/image-compare.tsx`.
- Registry dependencies, installed with it automatically: shadcn `utils` (cn), `lumen-foundation`.
- Builds: one set of files for both, but its dependencies come in Base UI and Radix builds. Install the one that matches the project (see Install): a free item's bare URL installs the Base UI build of it and its dependencies.
- Exports to keep: `ImageCompare`, `(before / after)`, `(handle)`, and every exported type.
- CSS: the install merges this item's rules (the registry `css` field) into your global stylesheet, in `@layer components`, and adds the lumen foundation (tokens, keyframes, motion levels) once. Nothing to import by hand.
- Re-running `add` (or `--overwrite`) re-applies those rules: put overrides in your own CSS, never in the installed rules.
- Tokens: retheme with the `--lumen-*` custom properties (`--lumen-accent`, `--lumen-accent-foreground`, `--lumen-accent-text`, `--lumen-bad`, `--lumen-bad-text`, `--lumen-chart-accent`, `--lumen-chart-accent-foreground`, `--lumen-chart-accent-text`, `--lumen-focus`, `--lumen-good`, `--lumen-good-text`, `--lumen-hairline`, `--lumen-ink`, `--lumen-muted-ink`, `--lumen-series-1`, `--lumen-series-2`, `--lumen-series-3`, `--lumen-series-4`, `--lumen-series-5`, `--lumen-series-6`, `--lumen-warn`, `--lumen-warn-text`); this item's CSS also reads `--lumen-font-mono`, `--lumen-radius-k`. Never add Tailwind colour classes inside the component.

```tsx
import { ImageCompare } from "@/components/ui/lumen/controls/image-compare";
```

## Parts

| Part | data-slot | What it is for |
|---|---|---|
| `ImageCompare` | — | The frame. |
| `(before / after)` | — | The two layers (image-compare-after for the other). |
| `(handle)` | — | The slider on the divider. |

## Sound
- Keep every `data-slot` and `data-sound` attribute: the sound layer reads them.
- Installing this item adds no audio. Nothing plays until the app mounts `GlassSoundProvider` once (install: `npx shadcn@latest add https://beautiful-ui.dev/r/glass-sound.json`, import from `@/components/beautiful-ui/glass-sound`); `GlassSoundToggle` is its mute control. Without a provider the audio engine never loads.

## Match the original
- Read `components/ui/lumen/controls/image-compare.tsx` as the reference implementation before changing or recreating anything, and match it: sizes, colours per theme, motion timings, copy and behaviour.
- If you deviate (a prop you can't honour, a style you changed, a dependency you swapped), say so in your reply, part by part.
- Keep the accessibility contract, the keyboard map and the motion levels listed below.

## Use it when
- image compare, before and after, comparison slider, image slider, before after photo, diff images, visual regression
- Before and after: a photo edit, a redesign, an upscaler, a visual regression
- Two renders of the same thing, aligned

### Not when
- Images that aren't the same size and framing: the divider only makes sense on aligned pictures
- More than two versions: use a carousel or tabs

## Mistakes
- Size the frame (aspect ratio or height): the images fill it
- Use images of the same framing, or the comparison misleads

## Usage

```tsx
"use client";

import { ImageCompare } from "@/components/ui/lumen/controls/image-compare";

export function GradeComparison() {
  return (
    <ImageCompare
      className="aspect-[3/2] w-full max-w-2xl"
      before={<img src="/photos/raw.jpg" alt="The photo as shot" />}
      after={<img src="/photos/graded.jpg" alt="The photo after grading" />}
    />
  );
}
```

## Props

| Prop | Type | Default | What it does |
|---|---|---|---|
| `before / after` | `ReactNode` |  | The two images (img, picture, video, svg…). Give each its own alt text. |
| `value / defaultValue / onValueChange` | `number / number / (value: number) => void` | `50` | How much of before shows, 0–100. |
| `orientation` | `"horizontal" \| "vertical"` | `"horizontal"` | A vertical divider moving sideways, or a horizontal one moving up and down. |
| `step / largeStep` | `number` | `1 / 10` | Arrow key step, and Shift+arrow or Page Up/Down. |
| `showLabels` | `boolean` | `true` | Before and After in the corners; each steps aside when the divider comes near. |
| `labels` | `Partial<{ handle, before, after, valueText }>` |  | The words, for other languages. |

Full docs: https://beautiful-ui.dev/components/lumen-image-compare

## Customising
- Colours: set the `--lumen-*` tokens on `:root`, or on a container with the `lumen-scope` class to retheme one area. Add the `lumen-inherit` class to follow your shadcn palette instead (`--chart-N`, `--destructive`).
- Dark mode follows the `.dark` class on an ancestor (the shadcn and next-themes convention).
- Update later by re-running the install with `--overwrite` (review the diff if you edited it). Changelog: https://beautiful-ui.dev/r/changelog.json

## Keyboard

| Keys | Action |
|---|---|
| Arrow keys | Move the divider 1% (Shift: 10%) |
| Page Up / Page Down | Move 10% |
| Home / End | All after / all before |

## Motion inventory

| Interaction | What moves |
|---|---|
| Drag | The divider follows the pointer exactly; the handle grows slightly while held, and the labels fade as the divider nears them |

## Accessibility contract (preserve when editing)
- The handle is a slider named Comparison divider, with its value as words ("60% before")
- Each image keeps its own alt text
- Dragging works anywhere in the frame; the keyboard reaches every position

## Install

```bash
npx shadcn@latest add @beautiful-ui-pro/lumen-image-compare
```

Pro item: needs the `@beautiful-ui-pro` registry in `components.json` and `BEAUTIFUL_UI_TOKEN` in `.env.local` (https://beautiful-ui.dev/account). Setup: https://beautiful-ui.dev/docs/pro. Your components.json `style` picks the build: radix-*, new-york and default get Radix, base-* gets Base UI.

## Credits
- Built on shadcn/ui (https://ui.shadcn.com)

The lumen foundation (the tokens listed above, keyframes and motion levels) installs once with the first component; its CSS is public at https://beautiful-ui.dev/r/lumen-foundation.json.