Modules

Ink API is modularized, so you can use only what you need.

Strokes

笔画模块是 Ink API 的基础。此模块中的关键数据类型包括：

• StrokeInputBatch：表示一系列指针输入，包括其位置、时间戳，以及可选的压力、倾斜度和方向。
• InProgressStroke：表示正在绘制的笔画。InProgressStroke 用于以低延迟渲染部分笔画，并在输入完成后构建最终的 Stroke，之后该对象可以重复使用。 InProgressStroke 由 InProgressStrokes 可组合项使用。
• Stroke：已完成的笔画的不可变表示形式，具有固定的几何形状。每个 Stroke 都有一个 ImmutableStrokeInputBatch（输入点）、一个 Brush（样式）和一个 PartitionedMesh（几何形状）。您可以在应用中存储、处理和渲染笔画。

Geometry

The Geometry module supports geometric operations on primitive shapes (using dedicated classes like Box and Vec), as well as arbitrary shapes (using PartitionedMesh), including intersection detection and transformation. PartitionedMesh can also hold additional data to support rendering.

Brush

The brush module defines the style of strokes. It consists of two main parts:

• Brush: Specifies the style of a stroke including base color, base size, and BrushFamily. BrushFamily is analogous to a font family, it defines a stroke's style. For example, a BrushFamily can represent a specific style of marker or highlighter, allowing strokes with different sizes and colors to share that style.
• StockBrushes: Provides factory functions for creating ready-to-use BrushFamily instances.

Authoring

The Compose Authoring module lets you capture user touch input and render it as low-latency strokes on the screen in real time. This is achieved through the InProgressStrokes composable, which processes motion events and displays the strokes as they are drawn.

Once a stroke is completed, the composable notifies the client application using an InProgressStrokesFinishedListener callback. This allows the application to retrieve the finished strokes for rendering or storage.

In Compose, InProgressStrokes takes this callback in the onStrokesFinished parameter. Pass the finished strokes to another composable to commit them to the screen using the rendering module.

Rendering

The Rendering module simplifies drawing ink strokes onto an Android Canvas. It provides CanvasStrokeRenderer for Compose and ViewStrokeRenderer for view-based layouts. These renderers optimize rendering performance and help deliver high-quality visuals, including antialiasing.

To render strokes, call the create() method to get a CanvasStrokeRenderer instance, and then call the draw() method to render either finished (Stroke) or in-progress (InProgressStroke) strokes onto a Canvas.

You can transform the canvas when you draw a stroke. Examples include panning, zooming, and rotating. To render the stroke correctly, you must also pass the canvas transform to CanvasStrokeRenderer.draw.

To avoid tracking the canvas transform separately, use ViewStrokeRenderer instead.

Storage

The storage module provides utilities for efficiently serializing and deserializing stroke data, primarily focusing on StrokeInputBatch.

The module uses protocol buffers and optimized delta compression techniques, resulting in significant storage savings compared to naive methods.

The storage module simplifies saving, loading, and sharing strokes.