bare-media

A set of media APIs for Bare

Install

npm i bare-media

Usage

Image:

import { image } from 'bare-media'

const preview = await image(path)
  .decode({ maxFrames })
  .resize({ maxWidth, maxHeight })
  .encode({ mimetype: 'image/webp' })

Video:

import { video } from 'bare-media'

const frames = video(path).extractFrames({ frameIndex })

Each method can also be used independently:

const rgba = await image.decode(buffer, { maxFrames })

Image API

decode()

Decode an image to RGBA

Parameter	Type	Description
buffer	object	The encoded image
opts.maxFrames	number	Max number of frames to decode in case of animated images

encode()

Encodes an image to a specific format

Parameter	Type	Description
buffer	object	The rgba image
opts.mimetype	string	The mimetype of the output image
opts.maxBytes	number	Max bytes for the encoded image (reduces quality or fps in case of animated images)
opts...	any	Additional encoder-specific options

crop()

Crop an image

Parameter	Type	Description
buffer	object	The rgba image
opts.left	number	Offset from left edge
opts.top	number	Offset from top edge
opts.width	number	Width of the region to crop
opts.height	number	Height of the region to crop

resize()

Resize an image

Parameter	Type	Description
buffer	object	The rgba image
opts.maxWidth	number	Max width of the output rgba
opts.maxHeight	number	Max height of the output rgba

slice()

Limits an animated image to a subset of frames. If the image is not animated, it returns the same rgba.

Parameter	Type	Description
buffer	object	The rgba image
opts.start	number	Frame index at which to start extraction. Default 0.
opts.end	number	Frame index at which to end extraction. Defaults to end of the animation

orientate()

Apply EXIF orientation.

Parameter	Type	Description
buffer	object	The rgba image
opts.file	Buffer	Optional. Input image used to extract EXIF metadata.
opts.exif	number	Optional. EXIF orientation value.
opts.transform	object	Optional. Transform object with rotate, flipH, and flipV.

At least one of opts.file, opts.exif, or opts.transform is required. In a pipeline, orientate() can be called without options:

const rgba = await image(path).decode().orientate()

rotate()

Rotate an image in 90-degree multiples.

Parameter	Type	Description
buffer	object	The rgba image
opts.deg	number	Rotation in degrees. Allowed values: [0, 90, 180, 270]

flip()

Flip an image horizontally or vertically.

Parameter	Type	Description
buffer	object	The rgba image
opts.h	boolean	Optional. Flip horizontally. Default true
opts.v	boolean	Optional. Flip vertically

read()

Read an image from a file path, URL, or buffer.

Parameter	Type	Description
input	object	File path, http(s) URL, or raw image buffer

save()

Write an encoded image buffer to a file.

Parameter	Type	Description
filename	string	Destination file path
buffer	object	Encoded image buffer
opts	object	Options passed through to fs.writeFile

metadata()

Important

This feature is experimental. The API is subject to change and may break at any time.

Read image metadata.

const data = await image(path).metadata()
const orientation = await image(path).metadata({ tag: 'orientation' })

Parameter	Type	Description
opts.tag	string	Optional. Read a single tag by name

Supported formats: jpeg, tiff.

metadata.strip()

Important

This feature is experimental. The API is subject to change and may break at any time.

Strip metadata from an image returning a new image buffer.

await image(path).metadata.strip().save(outPath)

Parameter	Type	Description
opts.keepColor	boolean	Keep color-transform metadata to avoid color shifts. Default true
opts.keepOrientation	boolean	Keep orientation to avoid image rotations. Default false

Check with isStripMetadataSupported() for supported types, only jpeg at the moment.

Video API

extractFrames()

Extracts frames from a video in RGBA

Parameter	Type	Description
opts.frameIndex	number	Number of the frame to extract

metadata()

Basic metadata for the primary video stream

Returns:

Field	Type	Description
width	number	Width of the primary video stream
height	number	Height of the primary video stream
codec.id	number	FFmpeg codec id of the primary video stream
codec.name	string	FFmpeg codec name of the primary video stream
duration	number	Stream duration in seconds
avgFramerate.numerator	number	Average frame rate numerator
avgFramerate.denominator	number	Average frame rate denominator
displayRotation	number	Rotation stored in display metadata
rotation	number	Corrective rotation to display the video upright
flipH	boolean	Whether the display metadata applies a horizontal flip
flipV	boolean	Whether the display metadata applies a vertical flip

Throws if the input has no video stream.

transcode()

Important

This feature is experimental. The API is subject to change and may break at any time.

Transcode a media file to a different format

Parameter	Type	Description
opts.format	string	Output format name (e.g., mp4, webm, matroska). Default mp4
opts.width	number	Width of the output video
opts.height	number	Height of the output video

Supported formats: mp4 (VP9+Opus), webm (VP9+Opus), matroska/mkv (VP9+Opus)

Example

import { video } from 'bare-media'

for await (const chunk of video('input.mkv').transcode({
  format: 'mp4',
  width: 1280,
  height: 720
})) {
  console.log('Received chunk:', chunk.buffer.length)
}

CLI

bare-media [flags] [command]

Flags:
  --version|-v   Print version
  --help|-h      Show help

Commands:
  metadata       Print image or video metadata (experimental)
  convert        Convert an image
  transcode      Transcode a video
  types          List supported MIME types

Supported Types

Helpers to check supported media types are exposed in bare-media/types:

• supportedImageMimetypes: list of supported image mimetypes.
• supportedVideoMimetypes: list of supported video mimetypes.
• isImageSupported(mimetype): returns true if the mimetype is a supported image format.
• isVideoSupported(mimetype): returns true if the mimetype is a supported video format.
• isMediaSupported(mimetype): returns true if the mimetype is either a supported image or video format.
• isStripMetadataSupported(mimetype): returns true if metadata.strip() supports the mimetype.

Detect the MIME type of a buffer:

import { detectMimeType } from 'bare-media'

const mimetype = detectMimeType(buffer)

This may return non-media MIME types, use isMediaSupported() to validate support.

License

Apache-2.0