add and document options for manipulating path

README.md

@@ -66,6 +66,17 @@ If no option is passed, you will get a random string of four characters and corr
 * `stroke`: 'black' // style/color of the svg path stroke
 * `fill`: 'black' // style/color of the svg strokes fill  
 
+Options that change the variation of the path:
+
+* `nodeDeviation: 0.1
+* `truncateLineProbability`: 0.5 
+* `truncateCurveProbability`: 0.5
+* `truncateCurvePositionMin`: 0.4
+* `truncateCurvePositionMax`: 0.6
+* `connectionPathDeviation` : 10.0
+
+(when using fill, set connectionPathDeviation far lower as it covers parts of the paths and is harder for humans to read - and consider converting it [to PNG](https://morioh.com/p/2a17965187b6) before serving, to stop bots from being able to read those obstructed paths)
+
 This function returns an object that has the following property:
 * `data`: string // svg path data
 * `text`: string // captcha text

index.d.ts

@@ -66,6 +66,36 @@ declare class ConfigObject {
 	 * max value of the math expression
 	 */
 	mathMax?: number;
+  /**
+   * default: 0.5
+   * changing line probabilities
+   */
+  truncateLineProbability?: number;
+  /**
+   * default: 0.5
+   * changing line probabilities
+   */
+  truncateCurveProbability?: number;
+  /**
+   * default: 0.4
+   * changing line probabilities
+   */
+  truncateCurvePositionMin?: number;
+  /**
+   * default: 0.6
+   * changing line probabilities
+   */
+  truncateCurvePositionMax?: number;
+  /**
+   * default: 10.0
+   * changing line probabilities
+   */
+  connectionPathDeviation?: number;
+  /**
+   * default: 0.2
+   * changing line probabilities
+   */
+  nodeDeviation?: number;
 }
 /**
  * result of captcha generation

lib/index.js

@@ -53,7 +53,7 @@ const createCaptcha = function (text, options) {
   /* Randomize nodes and randomly split them */
 	path = randomizePath(path, options);
   /* Join characters with random lines */
-	path = randomizePath.removeGaps(path);
+	path = randomizePath.removeGaps(path, options);
 
   /* Create xml */
 	const start = `<svg xmlns="http://www.w3.org/2000/svg" width="${width}" height="${height}" viewBox="0,0,${width},${height}">`;

lib/option-manager.js

@@ -21,7 +21,9 @@ const options = {
 	truncateLineProbability: 0.5,
 	truncateCurveProbability: 0.5,
 	truncateCurvePositionMin: 0.4,
-	truncateCurvePositionMax: 0.6
+	truncateCurvePositionMax: 0.6,
+  connectionPathDeviation: 10.0,
+  nodeDeviation: 0.2,
 };
 
 const loadFont = filepath => {

lib/randomize-path.js

@@ -1,8 +1,8 @@
 'use strict';
 const assert = require('assert');
 
-function rndPathCmd(cmd) {
-	const r = (Math.random() * 0.2) - 0.1;
+function rndPathCmd(cmd, deviation) {
+	const r = (Math.random() * deviation * 2) - deviation;
 
 	switch (cmd.type) {
 		case 'M':
@@ -145,7 +145,7 @@ function randomizePathNodes(commands, opts) {
  * @param qDist ratio of curves to lines
  * @return array of path commands
  */
-function connectPoints(xa, ya, xb, yb, qDist, avgDist) {
+function connectPoints(xa, ya, xb, yb, qDist, avgDist, deviation) {
 	const dist = distance(xa, ya, xb, yb);
 	const min = avgDist / 15;
 	const max = avgDist * 4;
@@ -155,12 +155,16 @@ function connectPoints(xa, ya, xb, yb, qDist, avgDist) {
 	const path = [];
 	while (drawDist < dist) {
 		const ratio = drawDist / dist;
-		const x = (xb - xa) * ratio + xa + Math.random() * 10 - 5;
-		const y = (yb - ya) * ratio + ya + Math.random() * 10 - 5;
+		const x = (xb - xa) * ratio + xa + Math.random()
+      * deviation * 2 - deviation;
+		const y = (yb - ya) * ratio + ya + Math.random()
+      * deviation * 2 - deviation;
 		const point = {};
 		if (Math.random() < qDist) {
-			const x1 = randomRange(xp, x) + Math.random() * 4 - 2;
-			const y1 = randomRange(yp, y) + Math.random() * 4 - 2;
+			const x1 = randomRange(xp, x) + Math.random()
+        * deviation - deviation / 2;
+			const y1 = randomRange(yp, y) + Math.random()
+        * deviation - deviation / 2;
 			point.type = 'Q';
 			point.x1 = x1;
 			point.y1 = y1;
@@ -181,7 +185,7 @@ function connectPoints(xa, ya, xb, yb, qDist, avgDist) {
 /*
  * Removes gaps in path (Z and following M command)
  */
-function removeGaps(path) {
+function removeGaps(path, options) {
 	if (!path.commands.length) {
 		return path;
 	}
@@ -234,6 +238,7 @@ function removeGaps(path) {
         prevCommand.x, prevCommand.y,
         nextCommand.x, nextCommand.y,
         qDist, avgDist,
+        options.connectionPathDeviation,
       );
 			commands = commands.concat(points);
 		} else {
@@ -247,7 +252,7 @@ function removeGaps(path) {
 
 module.exports = function (path, opts) {
 	// Randomize path commands
-	path.commands.forEach(rndPathCmd);
+	path.commands.forEach((c) => rndPathCmd(c, opts.nodeDeviation));
 	path.commands = randomizePathNodes(path.commands, opts);
 	return path;
 };

package.json

@@ -1,6 +1,6 @@
 {
   "name": "ppfun-captcha",
-  "version": "1.6.1",
+  "version": "1.6.2",
   "description": "Generate single-path svg captcha in node.js or express.js",
   "main": "index.js",
   "scripts": {