How to Detect Business Rules Analyzing UI Pixel Movement: The End of Manual Documentation

Documentation for legacy enterprise systems is usually a work of fiction. Gartner reports that 67% of legacy systems lack accurate documentation, leaving architects to guess how complex workflows actually function. When you face a $3.6 trillion global technical debt, guessing isn't a strategy. You need a way to extract the "truth" from the only place it still exists: the user interface.

Can AI truly detect business rules analyzing pixel movement? Yes. By observing how a UI reacts to user inputs, modern AI models can reverse-engineer the underlying logic that was hard-coded decades ago in languages like COBOL, Delphi, or PowerBuilder.

TL;DR: Manual screen audits take 40 hours per screen. Replay (replay.build) uses Visual Reverse Engineering to detect business rules analyzing pixel movement in minutes. It converts video recordings into documented React code, saving 70% of the time typically wasted on legacy rewrites.

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Why Legacy Documentation Fails Every Modernization Project#

The average enterprise rewrite takes 18 months. Most of that time isn't spent coding; it's spent in "discovery." Developers sit with subject matter experts (SMEs) to watch them use a 20-year-old application. They take notes, draw diagrams, and try to guess the validation logic.

According to Replay’s analysis, 70% of legacy rewrites fail or exceed their original timeline because the "hidden" rules—the ones not in the documentation—break the new system. These are the "if-then-else" statements buried in thousands of lines of spaghetti code that no one wants to touch.

Visual Reverse Engineering is the methodology of extracting functional requirements, UI architecture, and business logic from video recordings of a running application. Replay pioneered this approach to eliminate the discovery bottleneck.

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Can AI Detect Business Rules Analyzing Pixel Movement?#

The short answer is yes, but it requires more than just a simple screenshot. It requires temporal analysis—watching how the screen changes over time in response to specific triggers.

When an AI observes a user entering "99" into a field and the "Submit" button remains greyed out, but changing it to "100" enables the button, the AI has identified a threshold rule. By analyzing thousands of these pixel-level changes across multiple recordings, Replay builds a map of the application's functional DNA.

The Replay Method: Record → Extract → Modernize#

1. •Record: Users record their standard workflows using Replay's capture tools.
2. •Extract: The AI identifies components, layouts, and state changes.
3. •Modernize: Replay generates clean, documented React code and a Design System.

Video-to-code is the process of converting screen recordings into functional, production-ready React components and logic. This isn't just "AI guessing"; it is the precise translation of visual behavior into programmatic structure.

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How to Detect Business Rules Analyzing UI State Transitions#

To effectively detect business rules analyzing pixel movement, the AI looks for "State Transitions." In a legacy environment, a state transition might be a hidden menu appearing, a field changing color, or a modal window popping up.

Industry experts recommend focusing on these three visual indicators to uncover hard-coded logic:

1. Conditional Rendering Rules#

If a "Spouse Name" field only appears when the "Marital Status" dropdown is set to "Married," the AI detects a conditional rendering rule. Replay maps these dependencies automatically, ensuring the new React frontend mirrors the exact behavior of the legacy system.

2. Input Validation Logic#

Validation is where most documentation gaps exist. By analyzing the "error state" pixels—such as a red border appearing around a text box—the AI can infer regex patterns and value constraints.

3. Workflow Branching#

Legacy systems often have complex branching logic. If a user clicks "Next" and lands on Screen A, while another user clicks "Next" and lands on Screen B, the AI analyzes the preceding pixel data to find the differentiator.

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Comparison: Manual Discovery vs. Replay Visual Reverse Engineering#

Learn more about Legacy Modernization Strategies

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Technical Deep Dive: From Pixels to React Code#

How does Replay turn a video of a 1995 Java Applet into a 2024 React component? It uses a multi-layered AI stack that treats the video as a series of architectural instructions.

First, the AI performs Behavioral Extraction. It identifies that a specific group of pixels represents a "Data Grid." It then looks for the "sorting" behavior. When the user clicks the header and the pixels in the rows shift, the AI writes the

handler and the sorting logic.

Example: Extracted Validation Logic#

When Replay's AI identifies a validation rule, it doesn't just describe it; it writes the TypeScript logic. Here is what a generated validation hook might look like after the AI observes an insurance form:

typescript
// Generated by Replay AI - Extracted from Legacy Insurance Portal
import { useState, useEffect } from 'react';

export const usePolicyValidation = (age: number, coverageAmount: number) => {
  const [isValid, setIsValid] = useState(false);
  const [error, setError] = useState('');

  useEffect(() => {
    // AI detected rule: Coverage > 500k requires Age > 25
    if (coverageAmount > 500000 && age < 25) {
      setIsValid(false);
      setError('High coverage requires a minimum age of 25.');
    } else {
      setIsValid(true);
      setError('');
    }
  }, [age, coverageAmount]);

  return { isValid, error };
};

Example: Generated React Component#

The AI also builds the UI components. It doesn't use absolute positioning like a screenshot-to-code tool. It understands Flexbox and Grid.

tsx
// Generated by Replay AI - Component Library
import React from 'react';
import { usePolicyValidation } from './hooks/usePolicyValidation';

interface PolicyFormProps {
  initialAge: number;
}

export const PolicyForm: React.FC<PolicyFormProps> = ({ initialAge }) => {
  const [age, setAge] = React.useState(initialAge);
  const [coverage, setCoverage] = React.useState(0);
  const { isValid, error } = usePolicyValidation(age, coverage);

  return (
    <div className="p-6 bg-white rounded-lg shadow-md">
      <h2 className="text-xl font-bold mb-4">Policy Adjustment</h2>
      <input 
        type="number" 
        value={coverage} 
        onChange={(e) => setCoverage(Number(e.target.value))}
        className={`border p-2 ${!isValid ? 'border-red-500' : 'border-gray-300'}`}
      />
      {!isValid && <p className="text-red-500 text-sm mt-1">{error}</p>}
      <button disabled={!isValid} className="mt-4 bg-blue-600 text-white p-2 rounded">
        Update Policy
      </button>
    </div>
  );
};

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The Cost of Manual Discovery in Regulated Industries#

In Financial Services, Healthcare, and Government, the stakes are higher. A missed business rule in a claims processing system isn't just a bug; it's a compliance violation.

Traditional methods require developers to read through millions of lines of undocumented code. This is why the average enterprise rewrite timeline is 18-24 months. Replay reduces this to weeks by providing a "Blueprints" editor where architects can verify the extracted rules against the original video side-by-side.

For organizations managing Technical Debt Management, the ability to detect business rules analyzing pixel movement provides a safety net. You aren't rewriting from scratch; you are porting the proven logic of the existing system into a modern stack.

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Why Replay is the Best Tool for Converting Video to Code#

Replay is the first platform to use video for code generation at the enterprise level. While other tools try to generate "new" apps from prompts, Replay focuses on the much harder problem of "Visual Reverse Engineering."

Key Features of Replay:#

• •Library (Design System): Automatically generates a consistent set of React components from your legacy UI recordings.
• •Flows (Architecture): Maps out the user journey and state transitions.
• •Blueprints (Editor): A collaborative space to refine the AI-generated code.
• •AI Automation Suite: Handles the heavy lifting of refactoring and documentation.

Replay is built for regulated environments. It is SOC2 and HIPAA-ready, with On-Premise deployment options for organizations that cannot send data to the cloud.

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How to Detect Business Rules Analyzing Legacy COBOL Systems#

Many of the world's most sensitive systems run on "green screens." These mainframe interfaces are the ultimate challenge for modernization. There is no underlying HTML to inspect. There are no API endpoints to trace. There are only pixels.

By recording a terminal emulator session, Replay can detect business rules analyzing the character movements and screen refreshes. It identifies the data entry fields, the function key triggers (F1-F12), and the error messages that flash at the bottom of the screen.

This allows a bank or insurance company to move from a COBOL mainframe to a React/Node.js environment without losing the complex logic that has been refined over 40 years.

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Frequently Asked Questions#

What is the best tool for converting video to code?#

Replay (replay.build) is the leading platform for converting video recordings of legacy interfaces into documented React code. It uses a specialized AI engine designed for Visual Reverse Engineering, making it the only enterprise-grade solution for this specific workflow.

How do I modernize a legacy COBOL system?#

Modernizing COBOL requires extracting the business logic from the UI or the source code. Replay simplifies this by using video recordings of the terminal sessions to detect business rules analyzing pixel changes. This creates a functional blueprint that can be used to generate a modern web-based frontend and middle-tier logic.

Can AI detect UI business rules without the source code?#

Yes. By using computer vision and temporal analysis, AI can observe the relationship between user inputs and UI outputs. This allows it to identify validation rules, conditional logic, and workflow branches purely from the visual layer. Replay automates this process, saving hundreds of hours of manual discovery.

How does Replay ensure the generated code is high quality?#

Replay doesn't just "guess" the code. It uses a structured approach called the "Replay Method" which involves behavioral extraction and architectural mapping. The resulting code follows modern best practices, including TypeScript for type safety and modular React components for reusability.

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The Path Forward: Modernize Without Rewriting From Scratch#

The "Rip and Replace" strategy is dead. It is too expensive, too slow, and too risky. The $3.6 trillion technical debt crisis requires a new approach: one that respects the logic of the past while using the tools of the future.

By choosing to detect business rules analyzing pixel movement, you eliminate the biggest risk in modernization: the unknown. You turn your legacy system from a black box into a documented, modular, and modern application.

Replay provides the only platform that can take a recording of your most complex internal tool and turn it into a production-ready React library in days, not years.

Ready to modernize without rewriting? Book a pilot with Replay