Captcha4jk

Captcha4jk is a (Kotlin/Java) library for generating CAPTCHA challenge/answer pairs. Captcha4jk is intended to be easy to implement and use sensible defaults, while providing easily-accesssible hooks for customization.

Using the library

You can download and create the library source code as you like. Or use the jar file.

• Kotlin

val captcha = Captcha().builder(250, 100, "./", Color.white)
        .addLines(10, 10, 1, Color.black)
        .addNoise(false, Color.black)
        .setFont("Arial", 50, Font.BOLD)
        .setText(6, Color.black)
        .build()

captcha.answer // String
captcha.image  // File

• Java

Captcha captcha = new Captcha().builder(250, 100, "./", Color.white)
        .addLines(10, 10, 1, Color.black)
        .addNoise(false, Color.black)
        .setFont("Arial", 50, Font.BOLD)
        .setText(6, Color.black)
        .build();

captcha.getAnswer(); // String
captcha.getImage();  // File

Result

Methods

• builder

  Name	Type	Description
  width	Int	Image (CAPTCHA) width, default = 250
  height	Int	Image (CAPTCHA) height, default = 35
  path	String?	Image (CAPTCHA) path, If the path is null, the image will be saved as a temporary file
  background	Color?	Image (CAPTCHA) background color, If the background is null, a random RGB color will be used

• setFont

  Name	Type	Description
  name	String	The name of the font used to write the captcha, default = Arial
  size	Int	The font size used in the captcha, default = 24
  style	Int	Font style used in the captcha, default = Font.BOLD

• addLines

  Name	Type	Description
  vertical	Int	Number of vertical random lines, default = 10
  horizontal	Int	Number of horizontal random lines, default = 10
  width	Int	Width of lines, default = 1
  color	Color?	Lines color, If the color is null, a random RGB color will be used

  removeLines() : to remove lines.

• setText

  Name	Type	Description
  length	Int	CAPTCHA text length (in letters), default = 6
  color	Color?	Text color, If the color is null, a random RGB color will be used
  chars	List	The captcha text is randomly generated from a series of characters. The characters used can be customized as using numbers only or only letters. default = list('a'..'z' + '0'..'9')

• addNoise

  Name	Type	Description
  fill	Boolean	If you want to fill the image (CAPTCHA) with noises or make it random points, default = false
  color	Color?	Noise color, If the color is null, a random RGB color will be used

  removeNoises() : to remove noises.

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MIT License

Copyright (c) 2021 Merabet4mine

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.