From 2b649137530566a598977bbfdeb2bd979c302575 Mon Sep 17 00:00:00 2001
From: Christoph Reiter <reiter.christoph@gmail.com>
Date: Mon, 19 Oct 2020 11:41:50 +0200
Subject: [PATCH] qr-scanner: only check max 5 times per second for a QR code
Still raw the image and everything all the time to keep the experience smooth.
One more improvement would be to also skip the image data extraction, but that can
be done after the clipping work.
---
.../qr-code-scanner/src/qr-code-scanner.js | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/packages/qr-code-scanner/src/qr-code-scanner.js b/packages/qr-code-scanner/src/qr-code-scanner.js
index 820cf39a..796f2371 100644
--- a/packages/qr-code-scanner/src/qr-code-scanner.js
+++ b/packages/qr-code-scanner/src/qr-code-scanner.js
@@ -221,6 +221,9 @@ export class QrCodeScanner extends ScopedElementsMixin(DBPLitElement) {
requestAnimationFrame(tick);
}).catch((e) => { console.log(e); that.askPermission = true;});
+ let lastVideoTime = -1;
+ let lastCode = null;
+
function tick() {
if (that.sourceChanged) {
video.srcObject.getTracks().forEach(function(track) {
@@ -291,9 +294,19 @@ export class QrCodeScanner extends ScopedElementsMixin(DBPLitElement) {
imageData = canvas.getImageData(maskStartX , maskStartY, maskWidth, maskHeight);
}
- var code = jsQR(imageData.data, imageData.width, imageData.height, {
- inversionAttempts: "dontInvert",
- });
+ let code = null;
+ // We only check for QR codes 5 times a second to improve performance
+ let shouldAnalyze = Math.abs(lastVideoTime - video.currentTime) >= 1/5;
+ if (shouldAnalyze) {
+ lastVideoTime = video.currentTime;
+ code = jsQR(imageData.data, imageData.width, imageData.height, {
+ inversionAttempts: "dontInvert",
+ });
+ lastCode = code;
+ } else {
+ code = lastCode;
+ }
+
if (code) {
let topLeftCorner = code.location.topLeftCorner;
let topRightCorner = code.location.topRightCorner;
--
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