Raster is a composable image processing framework for building real-time still-image and video pipelines on Metal.

It is the actively maintained continuation of MetalPetal. Raster keeps the framework's lazy image model and established MTI* API vocabulary, while giving platform maintenance, documentation, and new development a clear home.

Raster 2.x changes the package, product, and module identity to Raster. MetalPetal 1.26 remains available from this repository as the final compatibility release under the MetalPetal product and module names. The migration guide explains the boundary and the small source change required to cross it.

What Raster does

An MTIImage is an immutable recipe rather than an eagerly rendered bitmap. Filters compose those recipes into a render graph, and an MTIContext evaluates the graph only when an application asks for pixels. That separation lets Raster reuse pipeline state, pool transient textures, share graph dependencies, and combine compatible render work before it reaches the GPU.

Raster includes render and compute kernels, a broad built-in filter set, two-image and multilayer compositing, explicit alpha and color handling, HDR-aware blend and CLAHE paths, Core Image and scene-framework bridges, CVPixelBuffer I/O, and typed Swift filter graphs.

Installation

Raster 2.x is distributed through Swift Package Manager:

.package(
    url: "https://github.com/aldealabs/raster.git",
    from: "2.0.0"
)

Select the Raster product for your target, then import the framework:

import Metal
import Raster

let device = MTLCreateSystemDefaultDevice()!
let context = try MTIContext(device: device)

let input = MTIImage(cgImage: sourceImage, isOpaque: true)
let output = input
    .adjusting(saturation: 0.8)
    .adjusting(exposure: 0.35)

let rendered = try context.makeCGImage(from: output)

Raster 2.x uses the Raster product and module; use the 1.26.0 tag when an application still needs import MetalPetal.

Documentation

The dedicated Raster documentation serves two audiences without mixing their level of abstraction:

• Framework users get installation, first-render, image I/O, composition, custom shader, video, HDR, interop, and performance guides.
• Framework maintainers get the promise resolver, graph optimizer, pipeline cache, shader generator, texture lifetime, concurrency, testing, and release contracts.

The site is a self-contained Next/MDX app. Run it locally with:

cd docs
npm ci
npm run dev

Examples

RasterExamples.xcodeproj contains iOS and macOS examples for still-image filters, live camera processing, blend modes, multilayer composition, CLAHE, bokeh, SceneKit, custom shaders, and video workflows.

Platform and package support

Raster supports iOS, macOS, tvOS, and Mac Catalyst. Swift Package Manager is the sole supported package manager. Device-specific Metal, Metal Performance Shaders, YCbCr, memoryless-texture, and programmable-blending capabilities are exposed through MTIContext.

Contributing and support

Read CONTRIBUTING.md before changing framework source or generated files. Use SUPPORT.md for support scope and SECURITY.md for private vulnerability reporting.

Raster is maintained by Aldea Labs. MetalPetal was created and developed primarily by YuAo; its authorship and history remain part of this repository and its license.

License

Raster is available under the MIT License. Files under RasterExamples/ use their separate example license.