Solves Math Captcha on the SkillRack website using Tesseract.js.
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// ==UserScript==
// @name SkillRack Math Captcha Solver
// @namespace http://tampermonkey.net/
// @version 0.4
// @description Solves Math Captcha on the SkillRack website using Tesseract.js.
// @author Bit-Blazer
// @license GNU GPLv3
// @match https://www.skillrack.com/faces/candidate/codeprogram.xhtml
// @match https://www.skillrack.com/faces/candidate/tutorprogram.xhtml
// @icon https://envs.sh/GiG.png
// @require https://cdn.jsdelivr.net/npm/tesseract.js@5/dist/tesseract.min.js
// @grant none
// ==/UserScript==
(function () {
"use strict";
// Define the IDs of the captcha image, input field, and proceed button
const CAPTCHA_INPUT = "capval";
const PROCEED_BTN = "proceedbtn";
/**
* Inverts the colors of the Captcha Image for better OCR results.
* This is useful for enhancing the text recognition capability of Tesseract.js.
* @param {HTMLImageElement} image - The image to be inverted.
* @returns {string} - Base64 encoded data URL of the inverted image.
*/
function invertColors(image) {
const canvas = document.createElement("canvas");
const ctx = canvas.getContext("2d");
canvas.width = image.width;
canvas.height = image.height;
ctx.drawImage(image, 0, 0);
ctx.globalCompositeOperation = "difference"; // Invert colors
ctx.fillStyle = "white"; // Set background to white
ctx.fillRect(0, 0, canvas.width, canvas.height); // Fill the canvas
return canvas.toDataURL(); // Return the inverted image as a data URL
}
/**
* Extracts the username from the span element.
* This function looks for the username pattern in the badge label.
* @returns {string} - The extracted username or an empty string if not found.
*/
function getUsername() {
const usernameElement = document.querySelector(".ui-badge-label"); // Select the username element
const match = usernameElement
? usernameElement.textContent.match(/(\d{12}@\w{3})/)
: null; // Match the username pattern
return match ? match[0] : ""; // Return the matched username or empty string
}
/**
* Solves the captcha by extracting numbers and performing the calculation.
* @param {string} text - The OCR result from the captcha image.
* @param {string} username - The username to be removed from the OCR text.
* @returns {number|null} - The result of the addition or null if not found.
*/
function solveCaptcha(text, username) {
// Remove the username from the OCR text and trim whitespace
const cleanedText = text.replace(new RegExp(username, "gi"), "").trim();
// Match the addition pattern in the cleaned text
const match = cleanedText.match(/(\d+)\s*\+\s*(\d+)/);
// Return the sum of the two numbers if a match is found
return match ? parseInt(match[1], 10) + parseInt(match[2], 10) : null;
}
/**
* Handles the captcha-solving process.
* This function orchestrates the overall captcha solving by coordinating image processing and user interactions.
*/
async function handleCaptcha() {
// Get the captcha elements from the DOM
const captchaImage = document.querySelector("img[src*='data:image']");
const captchaInput = document.getElementById(CAPTCHA_INPUT);
const proceedBtn = document.getElementById(PROCEED_BTN);
// Log an error and exit if any elements are not found
if (!captchaImage || !captchaInput || !proceedBtn) {
console.log("Captcha or input elements not found.");
return; // Stop execution
}
// Get the username from the UI
const username = getUsername();
// Invert the colors of the captcha image for better OCR processing
const invertedImg = invertColors(captchaImage);
try {
// Process the inverted image using Tesseract.js for OCR
const {
data: { text },
} = await Tesseract.recognize(invertedImg, "eng", {
whitelist:
"1234567890+=abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ@ ", // Allowed characters
psm: 6, // Page segmentation mode
});
// Solve the Captcha using the OCR text and username
const result = solveCaptcha(text, username);
// Notify if the captcha could not be solved
if (result === null) {
console.log("Unable to solve Captcha. Please try again.");
return; // Stop execution
}
// Fill the captcha input with the calculated result
captchaInput.value = result;
// Click the submit button to proceed
proceedBtn.click();
} catch (error) {
// Log any errors encountered during the OCR process
console.error("Error processing captcha:", error);
alert(
"An error occurred while processing the captcha. Please try again."
); // Notify user
}
}
// Wait for the window to fully load before handling the captcha
window.addEventListener("load", handleCaptcha);
})();