📚 break down documentation for github pages

docs/qr-codes.md

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+---
+layout: post
+title: QR Codes
+---
+
+An alternative way of communicating the secret to the user is through the use of [QR Codes](http://en.wikipedia.org/wiki/QR_code) which most if not all authenticator mobile apps can scan.
+
+This can avoid accidental typing errors and also pre-set some text values within the users app.
+
+You can display the QR Code as a base64 encoded image using the instance as follows, supplying the users name or other public identifier as the first argument
+
+````php
+<p>Scan the following image with your app:</p>
+<img src="<?php echo $tfa->getQRCodeImageAsDataUri('Bob Ross', $secret); ?>">
+````
+
+You can also specify a size as a third argument which is 200 by default.
+
+**Note:** by default, the QR code returned by the instance is generated from a third party across the internet. If the third party is encountering problems or is not available from where you have hosted your code, your user will likely experience a delay in seeing the QR code, if it even loads at all. This can be overcome with offline providers configured when you create the instance.
+
+## Online Providers
+
+[QRServerProvider](qr-codes/qr-server.html) (default)
+
+[ImageChartsQRCodeProvider](qr-codes/image-charts.html)
+
+[QRicketProvider](qr-codes/qrickit.html)
+
+## Offline Providers
+
+[EndroidQrCodeProvider](qr-codes/endroid.html) and EndroidQrCodeWithLogoProvider
+
+[BaconQRCodeProvider](qr-codes/bacon.html)
+
+**Note:** offline providers may have additional PHP requirements in order to function, you should study what is required before trying to make use of them.
+
+## Custom Provider
+
+If you wish to make your own QR Code provider to reference another service or library, it must implement the [IQRCodeProvider interface](https://github.com/RobThree/TwoFactorAuth/blob/master/lib/Providers/Qr/IQRCodeProvider.php).
+
+It is recommended to use similar constructor arguments as the included providers to avoid big shifts when trying different providers.
+
+## Using a specific provider
+
+If you do not want to use the default QR code provider, you can specify the one you want to use when you create your instance.
+
+```php
+use RobThree\Auth\TwoFactorAuth;
+
+$qrCodeProvider = new YourChosenProvider();
+
+$tfa = new TwoFactorAuth(
+	null,
+	6,
+	30,
+	'sha1',
+	$qrCodeProvider
+);
+```
+
+As you create a new instance of your provider, you can supply any extra configuration there.