Merge branch 'fix-jpeg-signatures' into 'master'

Fix camera jpeg signatures

See merge request meat-n-potatoes/pi-camera-connect!2

Author: gregnr

package.json

@@ -22,6 +22,9 @@
     "test": "jest --runInBand",
     "prepublishOnly": "yarn clean && yarn build"
   },
+  "dependencies": {
+    "systeminformation": "4"
+  },
   "devDependencies": {
     "@lcdev/eslint-config": "0.2",
     "@lcdev/jest": "0.2",

src/lib/still-camera.test.ts

@@ -5,5 +5,5 @@ test('takeImage() returns JPEG', async () => {
 
   const jpegImage = await stillCamera.takeImage();
 
-  expect(jpegImage.indexOf(StillCamera.jpegSignature)).toBe(0);
+  expect(jpegImage.indexOf(await StillCamera.getJpegSignature())).toBe(0);
 });

src/lib/still-camera.ts

@@ -1,5 +1,6 @@
+import * as si from 'systeminformation';
+import { Flip, Rotation } from '..';
 import { spawnPromise } from '../util';
-import { Rotation, Flip } from '..';
 
 export interface StillOptions {
   width?: number;
@@ -10,20 +11,6 @@ export interface StillOptions {
 }
 
 export default class StillCamera {
-  static readonly jpegSignature = Buffer.from([
-    0xff,
-    0xd8,
-    0xff,
-    0xe1,
-    0x64,
-    0x1a,
-    0x45,
-    0x78,
-    0x69,
-    0x66,
-    0x00,
-  ]);
-
   private readonly options: StillOptions;
 
   constructor(options: StillOptions = {}) {
@@ -35,6 +22,20 @@ export default class StillCamera {
     };
   }
 
+  static async getJpegSignature() {
+    const systemInfo = await si.system();
+    switch (systemInfo.model) {
+      case 'BCM2835 - Pi 3 Model B':
+      case 'BCM2835 - Pi 3 Model B+':
+      case 'BCM2835 - Pi 4 Model B':
+        return Buffer.from([0xff, 0xd8, 0xff, 0xe1]);
+      default:
+        throw new Error(
+          `Could not determine JPEG signature. Unknown system model '${systemInfo.model}'`,
+        );
+    }
+  }
+
   async takeImage() {
     try {
       return await spawnPromise('raspistill', [

src/lib/stream-camera.test.ts

@@ -11,7 +11,7 @@ test('Method takeImage() grabs JPEG from MJPEG stream', async () => {
 
   await streamCamera.stopCapture();
 
-  expect(jpegImage.indexOf(StreamCamera.jpegSignature)).toBe(0);
+  expect(jpegImage.indexOf(await StreamCamera.getJpegSignature())).toBe(0);
 });
 
 test('Method createStream() returns a stream of video data', async () => {