realsense-napi

Native N-API addon (C++) that wraps the Intel RealSense librealsense2 SDK so a TypeScript/Node.js CLI can capture depth + RGB frames from a D435i with a one-line call.

Requirements

• macOS (Apple Silicon tested) with the D435i connected via USB
• librealsense (2.58.4): brew install librealsense
• Node.js ≥ 18

macOS note: camera USB access requires root. Run your program with sudo.

Install & build

npm install        # installs deps and builds the native .node addon
npm run build      # or: node-gyp rebuild && tsc

You get:

• build/Release/realsense.node — the C++ native addon
• dist/ — compiled TS (wrapper, CLI, types)

Using it from TypeScript

import { capture, captureSync } from "./dist/realsense.js";

// async (non-blocking, worker thread)
const result = await capture({
  frames: 30,                                   // number of frames to grab
  depth: { width: 848, height: 480, fps: 10 },  // streaming modes
  color: { width: 1280, height: 720, fps: 15 },
});

const { color, depth, stats, device } = result;
console.log(device.name, device.serial);
console.log(`center distance: ${stats.centerMm} mm`);

// raw pixels
const rgb: Buffer = color.data;      // width*height*3 bytes, RGB order
const z16: Buffer = depth.data;      // width*height*2 bytes, uint16 LE
const m = (millimeters: number) => millimeters * depth.scale; // depth units

Sync version

const result = captureSync({ frames: 10 }); // blocks the event loop while capturing

API

All options are optional.

interface CaptureOptions {
  frames?: number;   // frames to average over (default 30, min 1)
  warmup?: number;   // frames to discard before measuring (default 5)
  depth?:  StreamConfig;
  color?:  StreamConfig;
}
interface StreamConfig { width?: number; height?: number; fps?: number; }

interface CaptureResult {
  device: { name: string; serial: string };
  color:  FrameInfo;               // width, height, data: Buffer (RGB8)
  depth:  DepthFrameInfo;          // width, height, data: Buffer (Z16), scale
  stats:  CaptureStats;
}
interface CaptureStats {
  fps: number;        // measured capture rate
  centerMm: number;   // depth at the center pixel (mm)
  validPct: number;   // pixels with valid depth (%)
  minM: number; meanM: number; maxM: number;  // depth range (meters)
}

Functions

| Function | Returns | Description | | ------------- | ---------- | --------------------------------------------- | | capture(options?) | Promise<CaptureResult> | Async capture on a worker thread | | captureSync(options?) | CaptureResult | Blocking capture (same result) | | getVersion() | string | SDK version string |

CLI

npm run build
sudo node dist/cli.js --out captures --frames 30 --depth 848x480@10 --color 1280x720@15

Saves a PPM (color) and PGM (16-bit depth) snapshot to captures/ and prints device + stats. Run sudo node dist/cli.js --help for options.

Working with the raw buffers

There is no image decoding in the addon — you get raw buffers and do whatever you want on the TS side:

import * as fs from "fs";
import { capture } from "./realsense";
import { PNG } from "pngjs";          // e.g. any encoder you like

const { color, depth } = await capture();

// wrap raw RGB into a PNG
const png = new PNG({ width: color.width, height: color.height });
Buffer.from(color.data).copy(png.data);       // rgb -> png synchronizes order
fs.writeFileSync("shot.png", PNG.sync.write(png));

Depth is in 16-bit Z16 (mm when depth.scale is 0.001). Apply data[i] * depth.scale to get meters.

Notes on this macOS setup

• Stable stream combo: depth 848×480@10 + color 1280×720@15 (not every mode/fps works)
• The IMU (gyro/accel) is not accessible on macOS — not exposed through the addon
• Some mode combos fail with failed to set power state right after plug-in; re-run or physically re-plug the camera