Add Image Stitcher web application

[simonw]

Summary

Add a complete web-based image stitching tool that allows users to horizontally stitch multiple images together with precise vertical alignment control.

Key Features

• Image Loading: Drag-and-drop or click-to-select multiple images (PNG, JPEG, WebP, GIF)
• Visual Alignment:
  • Drag images vertically to adjust alignment
  • Arrow keys for fine-tuning (1px or 10px increments)
  • Auto-align using edge luminance cross-correlation
• Interactive Editor:
  • Reorder images with left/right buttons
  • Real-time overlap previews showing seam areas (3x zoom)
  • Live stitched result canvas
  • Selection and nudge controls
• Export Options: Download as PNG or JPEG with adjustable quality
• Responsive Design: Works on desktop and mobile devices

Implementation Details

• Auto-alignment algorithm: Analyzes right edge of one image and left edge of the next using luminance-based cross-correlation to find optimal vertical offset
• Overlap previews: Shows 60px from each side of adjacent images at 3x zoom with a red seam line indicator
• Drag interaction: Uses Pointer Events API with capture for smooth dragging and visual feedback
• Performance: Throttled rendering during drag operations using requestAnimationFrame
• Accessibility: Keyboard shortcuts (arrow keys, Delete), semantic HTML, visually hidden file input

Technical Stack

• Vanilla JavaScript (no dependencies)
• HTML5 Canvas for image processing and rendering
• CSS Grid/Flexbox for responsive layout
• FileReader API for image loading

https://claude.ai/code/session_01Cf9UUauF9ZfjvFwnZMLs4F

[claude]

Claude finished @simonw's task —— View job

---

PR Review: Image Stitcher Web Application

I've completed a comprehensive review of the image stitcher web application. This is a well-implemented tool with impressive functionality for horizontal image stitching. Here's my detailed feedback:

Review Progress

• Read and analyze the image-stitcher.html file
• Review code quality and best practices
• Check for potential bugs or issues
• Evaluate performance considerations
• Assess security concerns
• Review test coverage
• Provide comprehensive review feedback

---

✅ Strengths

Code Quality & Architecture

• Well-structured vanilla JS: Clean separation of concerns with state management, event handling, and rendering functions
• Modern web APIs: Excellent use of Pointer Events, FileReader, Canvas APIs, and CSS Grid/Flexbox
• Accessibility: Good practices with semantic HTML, visually hidden file input, keyboard shortcuts (arrow keys, Delete)
• Responsive design: Mobile-friendly with media queries and touch-action CSS

Advanced Features

• Auto-alignment algorithm: Sophisticated luminance-based cross-correlation for edge matching (image-stitcher.html:366-444)
• Real-time overlap previews: Innovative 3x zoom view showing seam areas between images (image-stitcher.html:574-653)
• Smooth interactions: Proper pointer capture, throttled rendering during drag operations
• Export flexibility: PNG/JPEG with quality control

---

⚠️ Issues & Recommendations

Performance Considerations

1. Memory usage for large images (image-stitcher.html:673-674):

   resultCanvas.width = totalW;
   resultCanvas.height = totalH;

   • Issue: No limits on canvas size - could exceed browser memory limits
   • Recommendation: Add max canvas size validation (e.g., 32K x 32K pixels) and offer to downscale

2. Auto-align computation (image-stitcher.html:385-443):

   • Issue: Creates temporary canvases for each image pair without cleanup
   • Recommendation: Reuse canvas elements or add explicit cleanup

3. Image loading (image-stitcher.html:332-364):

   • Issue: All images loaded into memory simultaneously
   • Recommendation: Consider progressive loading for many/large images

Potential Bugs

1. Division by zero risk (image-stitcher.html:439):

   const mse = sse / count;

   • Issue: If count is 0, this creates NaN
   • Recommendation: Add if (count === 0) continue; before the division

2. Canvas context loss (image-stitcher.html:675):

   • Issue: No handling of WebGL context loss events
   • Recommendation: Add context loss detection and recovery

3. File input state (image-stitcher.html:263):

   • Issue: Input value cleared immediately, preventing same file re-selection
   • Current implementation: Actually handles this correctly with e.target.value = '';

Security Considerations

1. File type validation (image-stitcher.html:339):

   if (!file.type.startsWith('image/')) return;

   • Good: Basic MIME type checking
   • Enhancement: Consider magic number validation for additional security

2. Memory exhaustion (image-stitcher.html:695-705):

   • Issue: No limits on blob size or canvas dimensions
   • Recommendation: Add size limits to prevent DoS-style memory exhaustion

3. URL cleanup (image-stitcher.html:704):

   setTimeout(() => URL.revokeObjectURL(url), 3000);

   • Good: Proper cleanup of object URLs

Code Quality Improvements

1. Magic numbers (image-stitcher.html:244-245):

   const OVERLAP_PX = 60;
   const ZOOM_FACTOR = 3;

   • Good: Constants are properly defined
   • Enhancement: Consider making these user-configurable

2. Error handling:

   • Missing: No try-catch blocks around image operations
   • Recommendation: Add error handling for canvas operations and file reading

Test Coverage

• Current state: No automated tests present
• Recommendations:
  • Unit tests for auto-alignment algorithm
  • Integration tests for drag-and-drop functionality
  • Visual regression tests for rendering accuracy
  • Performance tests for large image handling

---

🔧 Suggested Improvements

1. Add canvas size limits:

   const MAX_CANVAS_AREA = 268435456; // 16K x 16K
   if (totalW * totalH > MAX_CANVAS_AREA) {
     // Offer to downscale or show warning
   }

2. Improve error handling:

   try {
     ctx.drawImage(im.img, x, im.offsetY - minY);
   } catch (e) {
     console.error('Canvas operation failed:', e);
     // Handle gracefully
   }

3. Add progress indicators for large operations (auto-align, rendering)

4. Memory optimization: Add option to work with downscaled previews and only render full resolution on export

---

📋 Overall Assessment

This is high-quality, production-ready code with impressive functionality. The auto-alignment algorithm is particularly sophisticated and the UI/UX is well-designed. The main concerns are around handling edge cases with very large images and adding comprehensive error handling.

Recommendation: ✅ Approve with minor enhancements

The code demonstrates excellent understanding of web APIs and image processing. The suggested improvements are mostly about robustness and edge case handling rather than fundamental issues.

[cloudflare-workers-and-pages]

Deploying tools with    Cloudflare Pages

Latest commit:	908ae3d
Status:	✅  Deploy successful!
Preview URL:	https://4f0e78f6.tools-b1q.pages.dev
Branch Preview URL:	https://claude-image-stitching-tool.tools-b1q.pages.dev

View logs

[claude]

Claude finished @simonw's task —— View job

---

PR Review: Image Stitcher Web Application

I've completed a comprehensive review of the image stitcher web application. This is a well-implemented tool with impressive functionality for horizontal image stitching. Here's my detailed feedback:

Review Progress

• Read and analyze the image-stitcher.html file
• Review code quality and best practices
• Check for potential bugs or issues
• Evaluate performance considerations
• Assess security concerns
• Review test coverage
• Provide comprehensive review feedback

---

✅ Strengths

Code Quality & Architecture

• Well-structured vanilla JS: Clean separation of concerns with state management, event handling, and rendering functions
• Modern web APIs: Excellent use of Pointer Events, FileReader, Canvas APIs, and CSS Grid/Flexbox
• Accessibility: Good practices with semantic HTML, visually hidden file input, keyboard shortcuts (arrow keys, Delete)
• Responsive design: Mobile-friendly with media queries and touch-action CSS

Advanced Features

• Auto-alignment algorithm: Sophisticated luminance-based cross-correlation for edge matching (image-stitcher.html:366-444)
• Real-time overlap previews: Innovative 3x zoom view showing seam areas between images (image-stitcher.html:574-653)
• Smooth interactions: Proper pointer capture, throttled rendering during drag operations
• Export flexibility: PNG/JPEG with quality control

---

⚠️ Issues & Recommendations

Performance Considerations

1. Memory usage for large images (image-stitcher.html:673-674):

   resultCanvas.width = totalW;
   resultCanvas.height = totalH;

   • Issue: No limits on canvas size - could exceed browser memory limits
   • Recommendation: Add max canvas size validation (e.g., 32K x 32K pixels) and offer to downscale

2. Auto-align computation (image-stitcher.html:385-443):

   • Issue: Creates temporary canvases for each image pair without cleanup
   • Recommendation: Reuse canvas elements or add explicit cleanup

3. Image loading (image-stitcher.html:332-364):

   • Issue: All images loaded into memory simultaneously
   • Recommendation: Consider progressive loading for many/large images

Potential Bugs

1. Division by zero risk (image-stitcher.html:439):

   const mse = sse / count;

   • Issue: If count is 0, this creates NaN
   • Recommendation: Add if (count === 0) continue; before the division

2. Canvas context loss (image-stitcher.html:675):

   • Issue: No handling of WebGL context loss events
   • Recommendation: Add context loss detection and recovery

3. File input state (image-stitcher.html:263):

   • Issue: Input value cleared immediately, preventing same file re-selection
   • Current implementation: Actually handles this correctly with e.target.value = '';

Security Considerations

1. File type validation (image-stitcher.html:339):

   if (!file.type.startsWith('image/')) return;

   • Good: Basic MIME type checking
   • Enhancement: Consider magic number validation for additional security

2. Memory exhaustion (image-stitcher.html:695-705):

   • Issue: No limits on blob size or canvas dimensions
   • Recommendation: Add size limits to prevent DoS-style memory exhaustion

3. URL cleanup (image-stitcher.html:704):

   setTimeout(() => URL.revokeObjectURL(url), 3000);

   • Good: Proper cleanup of object URLs

Code Quality Improvements

1. Magic numbers (image-stitcher.html:244-245):

   const OVERLAP_PX = 60;
   const ZOOM_FACTOR = 3;

   • Good: Constants are properly defined
   • Enhancement: Consider making these user-configurable

2. Error handling:

   • Missing: No try-catch blocks around image operations
   • Recommendation: Add error handling for canvas operations and file reading

Test Coverage

• Current state: No automated tests present
• Recommendations:
  • Unit tests for auto-alignment algorithm
  • Integration tests for drag-and-drop functionality
  • Visual regression tests for rendering accuracy
  • Performance tests for large image handling

---

🔧 Suggested Improvements

1. Add canvas size limits:

   const MAX_CANVAS_AREA = 268435456; // 16K x 16K
   if (totalW * totalH > MAX_CANVAS_AREA) {
     // Offer to downscale or show warning
   }

2. Improve error handling:

   try {
     ctx.drawImage(im.img, x, im.offsetY - minY);
   } catch (e) {
     console.error('Canvas operation failed:', e);
     // Handle gracefully
   }

3. Add progress indicators for large operations (auto-align, rendering)

4. Memory optimization: Add option to work with downscaled previews and only render full resolution on export

---

📋 Overall Assessment

This is high-quality, production-ready code with impressive functionality. The auto-alignment algorithm is particularly sophisticated and the UI/UX is well-designed. The main concerns are around handling edge cases with very large images and adding comprehensive error handling.

Recommendation: ✅ Approve with minor enhancements

The code demonstrates excellent understanding of web APIs and image processing. The suggested improvements are mostly about robustness and edge case handling rather than fundamental issues.