# Media and visual

Colours, image and page sizes, video and audio formats and subtitles.

## Topics

| Page | What it covers |
|---|---|
| [Colour](/docs/colour.md) | `Colour` is a colour as a web page uses it: written as CSS writes a hex colour, `#1e6fd9`, and held as its red, green, blue and alpha channels. |
| [Media](/docs/media.md) | The media types describe images, video, audio and captions: an image's size, a frame rate, a timecode, a subtitle cue, a film's age rating. |

## Types

| Type | What it is |
|---|---|
| [`Colour`](/docs/types/type-colour.md) | A colour, written `#1e6fd9`, or `#1e6fd980` when it isn't fully opaque. |
| [`ImageDimensions`](/docs/types/type-image-dimensions.md) | An image's width and height in pixels: `1920x1080`. |
| [`AspectRatio`](/docs/types/type-aspect-ratio.md) | Width to height in whole numbers: `16:9`. |
| [`Rect`](/docs/types/type-rect.md) | A rectangle by its top-left corner and its size, written like an SVG `viewBox`: `0 0 300 200`. |
| [`Insets`](/docs/types/type-insets.md) | Space inside each edge, written in CSS's order: `8 16 8 16`. |
| [`PaperSize`](/docs/types/type-paper-size.md) | A paper size: `A4`, `Letter` and so on. |
| [`ExifOrientation`](/docs/types/type-exif-orientation.md) | How a stored photo must be turned to look upright, as a camera records it. |
| [`AltText`](/docs/types/type-alt-text.md) | What an image shows, for someone who can't see it. |
| [`FrameRate`](/docs/types/type-frame-rate.md) | Frames a second, as an exact fraction: `25/1`, or `30000/1001` for 29.97. |
| [`VideoResolution`](/docs/types/type-video-resolution.md) | A video's frame size in pixels: `1920x1080`. |
| [`VideoCodec`](/docs/types/type-video-codec.md) | A video format as browsers name it: `avc1.42001E`, `vp09.00.10.08`. |
| [`AudioCodec`](/docs/types/type-audio-codec.md) | An audio format as browsers name it: `mp4a.40.2`, `opus`. |
| [`Timecode`](/docs/types/type-timecode.md) | An address of one frame in a video: hours, minutes, seconds and frames. |
| [`SubtitleCue`](/docs/types/type-subtitle-cue.md) | A timed caption: when it starts and ends, and its text. |
| [`ContentRating`](/docs/types/type-content-rating.md) | An age rating and the body that gave it: `BBFC 12A`. |
| [`ContentRatingScheme`](/docs/types/type-content-rating-scheme.md) | A body that rates films or games for age: `BBFC`, `MPA`, `PEGI` or `ESRB`. |