bun:image

Sharp-class image module — JPEG / PNG / WebP, resize, blur, sharpen, edges, rotate, crop, color adjust, alpha compositing.

import image from "bun:image";

A from-scratch image module with the codecs and operations Sharp covers, baked into the runtime. libjpeg-turbo, libpng, libwebp, and libsharpyuv are vendored statically — no npm install sharp, no Node-ABI-versioned binary distribution.

Images are Image objects: { width, height, channels, data: Uint8Array | Uint8ClampedArray }. Most operations return a new Image; the source is unchanged.

Codec I/O

decode(bytes)

Auto-detects format from magic bytes. JPEG, PNG, and WebP supported. Returns an Image with the file's native channel layout (RGB, RGBA, grayscale, grayscale-alpha).

const bytes = await Bun.file("photo.jpg").bytes();
const img = image.decode(bytes);
// { width: 1920, height: 1280, channels: 3, data: Uint8Array }

encode(img, opts)

const webp = image.encode(img, { format: "webp", quality: 85 });
const png  = image.encode(img, { format: "png" });
const jpg  = image.encode(img, { format: "jpeg", quality: 92, progressive: true });
await Bun.write("photo.webp", webp);

Geometric transforms

resize(img, opts)

const small = image.resize(img, { width: 800, height: 600, kernel: "lanczos" });
const fit   = image.resize(img, { width: 800, fit: "contain" });

rotate(img, degrees, opts?)

90 / 180 / 270 are exact transposes; arbitrary angles use bilinear interpolation. opts.background for the corner fill on non-quadrant rotations.

flip(img, axis)

axis is "horizontal", "vertical", or "both".

crop(img, { x, y, width, height })

Bounds are clamped to the image; out-of-bounds reads return the edge pixel.

Filters

blur(img, { sigma })

Separable Gaussian. Two 1-D passes. Edge mode: clamp.

boxBlur(img, { radius })

Faster, lower-quality alternative — good enough for cheap previews and the prefilter in sharpen.

sharpen(img, opts?)

Unsharp mask:

const sharp = image.sharpen(img, { amount: 1.5, sigma: 1.0, threshold: 0 });

edgeDetect(img, opts?)

Sobel. Returns a single-channel image of gradient magnitude. opts.normalize rescales the output to [0, 255].

Color

adjust(img, { brightness?, contrast?, saturation? })

Each value is a multiplier — 1.0 is no change, 1.5 is 50% boost. Saturation operates in HSL; brightness / contrast are linear in the RGB space.

hueShift(img, degrees)

YIQ rotation matrix. Preserves luma + saturation, rotates the chrominance angle. Pure hue shift; nothing else moves.

toGrayscale(img)

ITU-R BT.601 luma weights (0.299 R + 0.587 G + 0.114 B). Returns a single-channel image.

invert(img) / threshold(img, value)

Component-wise. threshold returns binary 0/255 per pixel based on luma.

histogram(img)

Returns { r: Uint32Array(256), g: Uint32Array(256), b: Uint32Array(256), a?: Uint32Array(256) } — per-channel value distribution. Useful for auto-levels / tone curves.

Compositing

composite(dst, src, opts?)

Porter-Duff source-over. Both images can have alpha.

const stamped = image.composite(canvas, watermark, { x: 20, y: 20, opacity: 0.6 });

Pipeline — chained operations

For longer chains, image.pipeline(img) returns a builder that defers work until the terminal call. This is where Sharp's lazy decode→transform→encode buffer sharing happens — operations short-circuit allocations of intermediate images.

const out = await image.pipeline(img)
  .resize({ width: 1024 })
  .blur({ sigma: 1.5 })
  .sharpen({ amount: 1.2 })
  .encode({ format: "webp", quality: 85 });

await Bun.write("processed.webp", out);

The terminal calls are .encode(opts), .toBuffer() (raw bytes), or .toImage() (back to a plain Image).

Performance

CPU release build, 4096² RGBA on a 16-core x86:

The kernel speedups are on isolated operations. End-to-end Sharp wins because libvips's lazy buffer chaining short-circuits intermediate decode + transform + encode allocations; image.pipeline closes most of that gap.

Limits

• AVIF decode/encode lands when libavif + aom (or dav1d) are vendored. Tracked.
• TIFF, GIF (animated), HEIF: not yet.
• ICC color management: not yet — output is sRGB-assumed.
• The pipeline builder fuses adjacent compatible kernels (e.g. resize + sharpen) but not all of them. This expands over time.