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https://github.com/g0dkar/qrcode-kotlin

QRCode Generator implemented in pure Kotlin
https://github.com/g0dkar/qrcode-kotlin

android java jvm kotlin qr-code qrcode qrcode-generator

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QRCode Generator implemented in pure Kotlin

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README 

        
# QRCode-Kotlin



[![License](https://img.shields.io/github/license/g0dkar/qrcode-kotlin)](LICENSE)

[![Maven Central](https://img.shields.io/maven-central/v/io.github.g0dkar/qrcode-kotlin.svg?label=Maven%20Central)](https://search.maven.org/search?q=g:%22io.github.g0dkar%22%20AND%20a:%22qrcode-kotlin%22)



💚 [_**Disponível em Português (Brasil)**_](README.pt-br.md) 💛



![QRCode Kotlin Logo](examples/kotlin/project-banner.png)



Creating QRCodes in Kotlin (and Java) is harder than it should be. **QRCode-Kotlin aims to bring a simple,

straightforward and customizable way to create QRCodes**, especially in the backend.



It is with this mission in mind that we keep doing our best to learn how developers use this library and their goals so

that we can provide a better library/API for them. Please, feel free to share if and how you're using this project ^^



* **Pure Kotlin:** Rewritten on pure Kotlin from a reference implementation of the QRCode spec

  by [Kazuhiko Arase](https://github.com/kazuhikoarase/qrcode-generator)

* **Lightweight:** No dependencies, `~115KB` and it does what it says on the tin.

* **Easy to use:** Quickly and easily implement QRCodes with few lines of code.

* **Good-looking:** Many developers don't have time and sometimes knowledge to implement the perfect QRCode,

  so this library tries to generate good-looking QRCodes by default.

* **Server friendly:** The JVM version is mainly focused on a personal use-case where I needed to generate QRCodes on

  the backend, but all libraries I found were either complex or huge, usually both.

* **Multiplatform:** This is a KMP library with support to Java, JavaScript, Android, iOS and tvOS.



## Table of Contents



* [Installation](#installation)

* [Usage](#usage)

    * [Spring Framework and/or Spring Boot](#spring-framework-andor-spring-boot)

* [License](#license)

* [Thanks and Acknowledgements](#thanks-and-acknowledgements)

* [Support and Links](#support-and-links)



## 1. Installation



The library is available

from [Maven Central](https://search.maven.org/artifact/io.github.g0dkar/qrcode-kotlin/4.1.0/qrcode-kotlin)

and [NPM JS](https://www.npmjs.com/package/qrcode-kotlin), so you can add it to your project as a dependency like any

other:



**Gradle:**



```groovy

// Use this for both Android and JVM

implementation("io.github.g0dkar:qrcode-kotlin:4.1.1")

```



**Maven - JVM:**



```xml



    io.github.g0dkar

    qrcode-kotlin-jvm

    4.1.1



```



**Maven - Android:**



```xml



    io.github.g0dkar

    qrcode-kotlin-android

    4.1.1



```



**NodeJS:**



```shell

npm install [email protected]

```



**Browser:**



```html



```



## Usage



To create QRCodes, the main class that should be used is the `qrcode.render.QRCode` class. It has static methods to help

you create a QRCode the way you want:



```kotlin

// Use one of these:



val squares = QRCode.ofSquares()



val circles = QRCode.ofCircles()



val roundedSquares = QRCode.ofRoundedSquares()

```



With that, you'll have a [QRCodeBuilder](src/commonMain/kotlin/qrcode/QRCodeBuilder.kt) instance. It has methods to

adjust colors, size, spacing, add a logo and more! Also, make sure to check

the [Colors](src/commonMain/kotlin/qrcode/color/Colors.kt) class as well.



Here's a code to get you started:



```kotlin

val helloWorld = QRCode.ofSquares()

    .withColor(Colors.DEEP_SKY_BLUE) // Default is Colors.BLACK

    .withSize(10) // Default is 25

    .build("Hello world!")



// By default, QRCodes are rendered as PNGs.

val pngBytes = helloWorld.render()



FileOutputStream("hello-world.png").use { it.write(pngBytes) }

```



We highly recommend that you check out some examples:



* [All sorts of shapes](examples/kotlin/src/main/kotlin/Example01-Shapes.kt): Squares, Circles, Rounded Squares and

  Custom shapes

* [All about colors](examples/kotlin/src/main/kotlin/Example02-Colors.kt): Foreground, Background, Transparent

  backgrounds, Linear Gradient colors

* [Adding a Logo](examples/kotlin/src/main/kotlin/Example03-Logo.kt): Add a logo and remove the cells behind it, or

  don't :)

* [SVG QRCodes](examples/kotlin/src/main/kotlin/Example04-SVG.kt): How to extend the renderer to render SVG (uses [JFree SVG](https://github.com/jfree/jfreesvg))

* [The banner on the top of this README](examples/kotlin/src/main/kotlin/ProjectLogo.kt): Yup, all done with the

  library ^^



The examples show pretty much all that can be done with the library! Even how to extend it so that it can create SVG

QRCodes ;)



You can mix and match all those together. Try generating the library logo and banner with gradients and all in SVG ;)



### Spring Framework and/or Spring Boot



As said earlier, one of the main reasons I developed this library was to use it on a backend application. So it is only

natural to show how to do that :)



This Spring Framework/Boot controller method can generate QRCodes of a given content:



```kotlin

import org.springframework.core.io.ByteArrayResource

import org.springframework.http.HttpHeaders.CONTENT_DISPOSITION

import org.springframework.http.MediaType.IMAGE_PNG_VALUE



@GetMapping("/qrcode")

fun generateQrCode(content: String): ResponseEntity {

    val pngData = QRCode().ofSquares()

        .build(content)

        .render()

    val resource = ByteArrayResource(pngData, IMAGE_PNG_VALUE)



    return ResponseEntity.ok()

        .header(CONTENT_DISPOSITION, "attachment; filename=\"qrcode.png\"")

        .body(resource)

}

```



## Changes from v3



The main changes coming from `v3.3.0` are:



1. The main package of the classes was changed from `io.github.g0dkar.qrcode` to simply `qrcode`

    * The old name doesn't help languages that don't have the "package" concept, and other Kotlin libraries already name

      their main package this way.

2. The old `QRCode` class was rewritten to be easier to create better looking QRCodes . The previous `QRCode` class was

   renamed to [QRCodeProcessor](src/commonMain/kotlin/qrcode/raw/QRCodeProcessor.kt), with very minor API changes.

    * **For most of the simple cases, the new `QRCode` class is compatible with the old one!**

3. A bunch of optimizations on how the QRCode is drawn. Previously, we'd had a canvas for each square, which would then

   be copied into the QRCode. This was changed to have just one large canvas where each square will be individually

   drawn directly.

4. iOS and tvOS Support: Starting from `v4.0.7` an initial implementation of the `QRCodeGraphics` so that iOS and tvOS

   are now supported. **Any and all [feedback](https://github.com/g0dkar/qrcode-kotlin/issues/85) are very welcome!** -

   Thanks a lot to [ruicanas](https://github.com/ruicanas) for all his contributions to this feature :D



## License



Copyright since 2021 Rafael M. Lins, Licensed under the [MIT License](https://rafaellins.mit-license.org/2021/).



QR Code is trademarked by Denso Wave, Inc.



## Thanks and Acknowledgements



* [Kazuhiko Arase](https://github.com/kazuhikoarase): For his reference implementation!

* [Paul Varry](https://github.com/pvarry): for opening the first few issues on the repo and helping to make the library

  even better for everyone! :grin:

* [Renan Lukas](https://github.com/RenanLukas): For his friendship, patience and help with Android, Gradle and a bunch

  of other stuff during the development of v2.0.0 and v3.0.0!

* [Doomsdayrs](https://github.com/Doomsdayrs): For pointing out how the library could be improved using Kotlin

  Multiplatform, and helping out implementing it into the project.

* An awesome, furry friend for all the support through all these years :)

* [ruicanas](https://github.com/ruicanas): For not only pointing out some issues with the iOS implementation, but also

  fixing them! Thank you so much ^^



## Support and Links



* If you found any bugs,

  please [open an Issue](https://github.com/g0dkar/qrcode-kotlin/issues/new?assignees=g0dkar&labels=bug&template=bug_report.md&title=)

  😁

* Have any suggestions? You

  can [make them](https://github.com/g0dkar/qrcode-kotlin/issues/new?assignees=&labels=&template=feature_request.md&title=)

  as well!



If you enjoyed the library and want to get me some coffee, use the buttons below :love_you_gesture:



[Buy me a coffee over at Ko-fi!](https://ko-fi.com/g0dkar)



[Buy me a coffee over at PayPal!](https://www.paypal.com/donate/?business=EFVC68BFJQWSC&no_recurring=0&item_name=Rafael+is+working+on+Open+Source+software+in+his+free+time.+This+helps+him+keep+this+up+for+longer%2C+and+with+higher+quality%21&currency_code=BRL)