https://github.com/twsl/kaptcha.net

Kaptcha.NET is simple captcha library for .NET Core projects
https://github.com/twsl/kaptcha.net

captcha captcha-alternative netcore netstandard

Last synced: 27 days ago
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Kaptcha.NET is simple captcha library for .NET Core projects

• Host: GitHub
• URL: https://github.com/twsl/kaptcha.net
• Owner: twsl
• License: mit
• Created: 2019-07-01T18:35:29.000Z (almost 6 years ago)
• Default Branch: master
• Last Pushed: 2020-08-10T12:29:02.000Z (almost 5 years ago)
• Last Synced: 2025-04-02T09:51:16.214Z (about 2 months ago)
• Topics: captcha, captcha-alternative, netcore, netstandard
• Language: C#
• Size: 758 KB
• Stars: 5
• Watchers: 0
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

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README

        
# Kaptcha.NET

[![Build Status](https://dev.azure.com/twsl/Kaptcha.NET/_apis/build/status/twsI.Kaptcha.NET?branchName=master)](https://dev.azure.com/twsl/Kaptcha.NET/_build/latest?definitionId=6&branchName=master) ![Nuget](https://img.shields.io/nuget/v/Kaptcha.NET.svg) ![Nuget (with prereleases)](https://img.shields.io/nuget/vpre/Kaptcha.NET.svg)

Kaptcha.NET is simple captcha library for .NET Core projects.

## Motivation

With Google's [reCAPTCHA](https://en.wikipedia.org/wiki/ReCAPTCHA) beeing the de facto standard solution for captchas nowadays, it is pretty much the opposite of a privacy respecting solution. It collects substantial information which can be used to track users and makes complying with GDPR much more complicated.

Therefore I wanted to create a minimalistic, privacy respecting solution, which is simple to implement, yet sufficiently difficult to solve.

## Examples

| | | | |

|-|-|-|-|

|![alt-text-1](./img/1.png "Example 1") | ![alt-text-2](./img/2.png "Example 2") | ![alt-text-3](./img/3.png "Example 3") | ![alt-text-4](./img/4.png "Example 4") |

|![alt-text-5](./img/5.png "Example 5") | ![alt-text-6](./img/6.png "Example 6") | ![alt-text-7](./img/7.png "Example 7") | ![alt-text-8](./img/8.png "Example 8") |

## Install

Install the nuget package `Kaptcha.NET`.

## Getting Started

* Add the required captcha services via the service collection extension. You have to use a Cache Provider. You can use SQL Server Cache, In Memory Cache or Distributed Cache (like a Redis).

```csharp

public void ConfigureServices(IServiceCollection services)

{

	//...

	services.AddDistributedMemoryCache(); // Required for the specific default implementation of ICaptchaStorageService

	services.AddCatpcha(Configuration);

	//...

}

```

* In case you prefer to create and use your own, custom implementation of any service, replace '.AddCatpcha(Configuration)' with the following and use your own classes:

```csharp

public void ConfigureServices(IServiceCollection services)

{

	//...

	services.AddCatpchaOptions(configuration);

			.AddCaptchaFontGenerator();

			.AddCaptchaEffect();

			.AddCaptchaKeyGenerator();

			.AddCatpchaGenerator();

			.AddCaptchaStorage();

			.AddCaptchaValidator();

			.AddScoped(typeof(ValidateCaptchaFilter));

	//...

}

```

* Add the TagHelper to the `_ViewImports.cshtml`

```csharp

@addTagHelper *, Kaptcha.NET

```

* Actually adding the captcha into the ViewPage afterwards is as simple as 

```html

```

* If you want to provide a direkt link to a captcha, add a new controller and inherit from `Controllers\CaptchaController.cs`, which provides all requied methods.

```razor

@{

	var captcha = await generator.CreateCaptchaAsync();

}

```

* Or you can use controller and actions instead of a direct link and let the TagHelper generate the captcha on it'S own.

```html

```

## Configuration

You can configure the following options:

* Image height (default: `250`)

* Image Width (default: `100`)

* Scaling (default: `2`)

* Background color (default: `Color.White`)

* Foreground color (default: `Color.Black`)

* Number of characters (default: `5 - 8`)

* Charset (default: `"abcdefghijklmnopqrstuvwxyz"`)

* Rotation angle (default: `-30 - 30`)

* Imageformt (default: `PNG`)

* Validation Timeout (default: `5min`)

* Font family (default: `Arial`)

* Font size (default: `22 - 30`)

* Font style (default: `regular`)

To change the default values you need to set the appropriate properties in eigher the `CaptchaOptions` or `FontOptions`. 

Moreover you can enable different effects within the `EffectOptions`.

* `BlobEffect`

* `BoxEffect`

* `LineEffect`

* `NoiseEffect`

* `RippleEffect`

* `WaveEffect`

In ASP.NET Core projects, you can do this via the `appsettings.json` file, an example is provided under `test\Kaptcha.NET.Web`.

## TODO

Currently, `System.Drawing.Common` is used. I plan on replacing it in the future. To use it on Linux, add the following commands to your docker file

```

sudo apt install libc6-dev 

sudo apt install libgdiplus

```

and consider checking out this [blog post](https://www.hanselman.com/blog/HowDoYouUseSystemDrawingInNETCore.aspx) by Scott Hanselman.