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Build an image comparison tool

Written by

Bernardo Palos

in

Here’s a basic implementation of an Image Comparison Tool using HTML, CSS, and JavaScript. This tool allows you to compare two images using a slider that reveals one image over another.

html
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
  <title>Image Comparison Tool</title>
  <style>
    * {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      font-family: Arial, sans-serif;
      background: #f4f4f4;
      display: flex;
      justify-content: center;
      align-items: center;
      height: 100vh;
    }

    .container {
      position: relative;
      width: 700px;
      max-width: 100%;
      overflow: hidden;
      box-shadow: 0 5px 15px rgba(0,0,0,0.2);
    }

    .img-wrapper {
      position: relative;
      width: 100%;
    }

    .img-wrapper img {
      width: 100%;
      display: block;
    }

    .overlay {
      position: absolute;
      top: 0;
      left: 0;
      overflow: hidden;
      width: 50%;
    }

    .slider {
      position: absolute;
      top: 0;
      left: 50%;
      width: 4px;
      height: 100%;
      background: #fff;
      cursor: ew-resize;
      z-index: 10;
    }

    .slider::before {
      content: '';
      position: absolute;
      top: 50%;
      left: -8px;
      width: 20px;
      height: 20px;
      background: #007BFF;
      border-radius: 50%;
      transform: translateY(-50%);
      box-shadow: 0 2px 6px rgba(0,0,0,0.3);
    }
  </style>
</head>
<body>
  <div class="container" id="compareContainer">
    <div class="img-wrapper">
      <img src="image1.jpg" alt="Image 1">
      <div class="overlay" id="imgOverlay">
        <img src="image2.jpg" alt="Image 2">
      </div>
      <div class="slider" id="slider"></div>
    </div>
  </div>

  <script>
    const container = document.getElementById('compareContainer');
    const slider = document.getElementById('slider');
    const overlay = document.getElementById('imgOverlay');

    let isDown = false;

    slider.addEventListener('mousedown', () => isDown = true);
    slider.addEventListener('touchstart', () => isDown = true);

    window.addEventListener('mouseup', () => isDown = false);
    window.addEventListener('touchend', () => isDown = false);

    window.addEventListener('mousemove', drag);
    window.addEventListener('touchmove', drag);

    function drag(e) {
      if (!isDown) return;

      const rect = container.getBoundingClientRect();
      const x = e.touches ? e.touches[0].clientX : e.clientX;
      let position = x - rect.left;

      if (position < 0) position = 0;
      if (position > rect.width) position = rect.width;

      overlay.style.width = position + 'px';
      slider.style.left = position + 'px';
    }
  </script>
</body>
</html>

How to Use:

  • Replace image1.jpg and image2.jpg with paths to your own images.

  • Open the HTML file in a browser to interact with the comparison slider.

Let me know if you need this in a React or Vue component, or want features like zoom, annotation, or mobile responsiveness.

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