Wakabtcha consists of two independend modules: for generating random text (captcha answers) and for generating images from text (captcha questions). It doesn't have any database handling and verification logic, just challenge itself. It is an accurate port of captcha.pl from original Wakaba written by Dag Ågren (!WAHa.06x36) and produces 100% identical result on binary level. Customisation capabilities include user-defined fonts, grammar, level of randomization and styling.

Basic usage

const wakabtcha = require('wakabtcha');
const fs = require('fs');

const answer = wakabtcha.generateAnswer();
const image = wakabtcha.generateImage(answer);
// save buffer to file system
fs.writeFile(`${answer}.gif`, image, console.log);

generateAnswer options

wakabtcha.generateAnswer(start = '%W%', grammar = DEFAULT_GRAMMAR)

generateImage options

wakabtcha.generateImage(str, options)

Answers generation can be changed, for example, to generate answers with different writing systems or character sets. Generation of answers based on L-system. L-system starts with axiom string, that acts as a template. Grammar object describes rules of L-system. All substrings in initial axiom enclosed in % symbols (e.g. "%W%") are recursively replaced by random string from array from grammar object's field where key matches substring. Example: "%W%" => "%C%%T%" => "l%V%%F%" => "lock"

Example 1: Default configuration

const DEFAULT_GRAMMAR = {
  'W': ['%C%%T%', '%C%%T%', '%C%%X%', '%C%%D%%F%', '%C%%V%%F%%T%', '%C%%D%%F%%U%', '%C%%T%%U%', '%I%%T%', '%I%%C%%T%', '%A%'],
  'A': ['%K%%V%%K%%V%tion'],
  'K': ['b', 'c', 'd', 'f', 'g', 'j', 'l', 'm', 'n', 'p', 'qu', 'r', 's', 't', 'v', 's%P%'],
  'I': ['ex', 'in', 'un', 're', 'de'],
  'T': ['%V%%F%', '%V%%E%e'],
  'U': ['er', 'ish', 'ly', 'en', 'ing', 'ness', 'ment', 'able', 'ive'],
  'C': ['b', 'c', 'ch', 'd', 'f', 'g', 'h', 'j', 'k', 'l', 'm', 'n', 'p', 'qu', 'r', 's', 'sh', 't', 'th', 'v', 'w', 'y', 's%P%', '%R%r', '%L%l'],
  'E': ['b', 'c', 'ch', 'd', 'f', 'g', 'dg', 'l', 'm', 'n', 'p', 'r', 's', 't', 'th', 'v', 'z'],
  'F': ['b', 'tch', 'd', 'ff', 'g', 'gh', 'ck', 'll', 'm', 'n', 'n', 'ng', 'p', 'r', 'ss', 'sh', 't', 'tt', 'th', 'x', 'y', 'zz', 'r%R%', 's%P%', 'l%L%'],
  'P': ['p', 't', 'k', 'c'],
  'Q': ['b', 'd', 'g'],
  'L': ['b', 'f', 'k', 'p', 's'],
  'R': ['%P%', '%Q%', 'f', 'th', 'sh'],
  'V': ['a', 'e', 'i', 'o', 'u'],
  'D': ['aw', 'ei', 'ow', 'ou', 'ie', 'ea', 'ai', 'oy'],
  'X': ['e', 'i', 'o', 'aw', 'ow', 'oy']
};

Example 2: Simple numeric code

const numbersGrammar = {
  'N': [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]
};

// will generate 6-digit code
wakabtcha.generateAnswer('%N%%N%%N%%N%%N%%N%', numbersGrammar)

Appearance of every letter is described by font object. Keys of this object are characters, characters that are missing in font will not be rendered. Values are array where first element is character width, and subseuqet elements are strokes. Stroke is 1-dimensional array of coordinates that form path of series of straight lines in form [x0,y0, x1,y1, x2,y2, ..., xN,yN]. Coordinate system origin is top left corner.

Example 1: Default font

const DEFAULT_FONT = {
  'a': [4, [0, 2, 1, 1, 2, 1, 3, 2, 3, 5, 4, 6], [3, 3, 1, 3, 0, 4, 0, 5, 1, 6, 2, 6, 3, 5]],
  'b': [3, [0, 0, 0, 6, 2, 6, 3, 5, 3, 4, 2, 3, 0, 3]],
  'c': [3, [3, 6, 1, 6, 0, 5, 0, 4, 1, 3, 3, 3]],
  'd': [3, [3, 0, 3, 6, 1, 6, 0, 5, 0, 4, 1, 3, 3, 3]],
  'e': [3, [3, 6, 1, 6, 0, 5, 0, 3, 1, 2, 3, 2, 3, 3, 2, 4, 0, 4]],
  'f': [3, [1, 6, 1, 1, 2, 0, 3, 0], [0, 3, 2, 3]],
  'g': [3, [3, 6, 1, 6, 0, 5, 0, 4, 1, 3, 3, 3, 3, 7, 2, 8, 0, 8]],
  'h': [3, [0, 0, 0, 6], [0, 3, 2, 3, 3, 4, 3, 6]],
  'i': [2, [1, 3, 1, 6], [1, 1, 1.5, 1.5, 1, 2, 0.5, 1.5]],
  'j': [3, [2, 3, 2, 7, 1, 8, 0, 7], [2, 1, 2.5, 1.5, 2, 2, 1.5, 1.5]],
  'k': [3, [0, 0, 0, 6], [0, 4, 1, 4, 2, 2], [0, 4, 1, 4, 3, 6]],
  'l': [2, [0.5, 0, 0.5, 5, 1.5, 6]],
  'm': [4, [0, 6, 0, 3, 1, 3, 2, 4], [2, 6, 2, 3, 3, 3, 4, 4, 4, 6]],
  'n': [3, [0, 3, 0, 6], [0, 4, 1, 3, 2, 3, 3, 4, 3, 6]],
  'o': [3, [0, 4, 1, 3, 2, 3, 3, 4, 3, 5, 2, 6, 1, 6, 0, 5, 0, 4]],
  'p': [3, [0, 8, 0, 3, 2, 3, 3, 4, 3, 5, 2, 6, 0, 6]],
  'q': [3, [3, 6, 1, 6, 0, 5, 0, 4, 1, 3, 3, 3, 3, 8], [2, 7, 4, 7]],
  'r': [3, [0, 3, 0, 6], [0, 4, 1, 3, 2, 3]],
  's': [3, [0, 6, 2, 6, 3, 5, 0, 4, 1, 3, 3, 3]],
  't': [3, [1, 1, 1, 5, 2, 6], [0, 3, 2, 3]],
  'u': [3, [0, 3, 0, 6, 2, 6, 3, 5, 3, 3]],
  'v': [3, [0, 3, 1.5, 6, 3, 3]],
  'w': [4, [0, 3, 0, 5, 1, 6, 2, 5, 3, 6, 4, 5, 4, 3]],
  'x': [3, [0, 3, 3, 6], [0, 6, 3, 3]],
  'y': [3, [0, 3, 0, 5, 1, 6, 3, 6], [3, 3, 3, 7, 2, 8, 0, 8]],
  'z': [3, [0, 3, 3, 3, 0, 6, 3, 6], [0.5, 4.5, 2.5, 4.5]],
  ' ': [3],
};

Example 2: Font with numbers

Font by @OMOTO-TK

const myFont = {
	'1': [2,[1,1,1,6],[-1,2,1,1]],
	'0': [3,[0,4,1,2,2,2,3,3,3,5,2,6,1,6,0,5,0,4]],
	'2': [3,[-1,3,1,1,3,1],[3,1,0,5],[0,5,5,5]],
	'3': [3,[-1,3,1,1,3,1],[3,1,1,4],[1,4,3,5],[3,5,-1,7]],
	'4': [3,[0,0,0,3],[0,3,4,3],[4,3,4,0],[4,3,4,8]],
	'5': [3,[5,0,0,0],[0,0,0,2],[0,2,3,2],[3,2,3,6],[3,6,0,6]],
	'6': [3,[5,0,4,1,3,2,2,3,1,4],[1,4,0,5,0,6,3,6,3,5,1,4]],
	'7': [3,[0,0,6,0],[6,0,0,6]],
	'8': [3,[0,4,1,3,2,3,3,4,3,5,2,6,1,6,0,5,0,4],[1,3,2,3,3,3,3,2,2,0,1,0,0,2,0,3,1,3]],
	'9': [3,[1,3,2,3,3,3,3,2,2,0,1,0,0,2,0,3,1,3],[3,3,0,7]],
	' ': [3],
};

wakabtcha.generateImage('123456', { font: myFont });