Version 1.9.1.92 represents the most significant update to AltaLux since its initial release. This version brings critical bug fixes, substantial performance improvements, comprehensive documentation, and enhanced user experience.
🎯 Critical Bug Fix: Color Preservation
The Problem
Previous versions used an incorrect algorithm for preserving color when applying luminance enhancements. The old additive approach (R' = R + ΔY) changed color ratios, causing:
- Hue shifts: Colors changed their actual hue (blue → cyan, red → orange)
- Desaturation: Vibrant colors became washed out
- Unnatural results: Enhanced images looked artificial
Example of the bug:
Original pixel: RGB(50, 100, 200) - Deep blue
Old algorithm: RGB(100, 150, 250) - Shifted to cyan/white ❌
New algorithm: RGB(100, 200, 400→255) - Preserved blue hue ✅The Fix
I have completely rewritten the color preservation algorithm to use multiplicative scaling:
// Old (WRONG): Additive method
R' = R + ΔY
G' = G + ΔY
B' = B + ΔY
// New (CORRECT): Multiplicative method
scale = Y_new / Y_old
R' = R × scale
G' = G × scale
B' = B × scaleThis preserves the exact color ratios, maintaining hue and saturation perfectly while applying the enhancement.
Impact: All processed images now maintain their original colors while benefiting from improved local contrast. This was the most critical fix in this release.
🎨 User Experience Improvements
Native Dark Mode Support
AltaLux now fully supports Windows 10/11 dark mode with automatic theme detection:
- Automatic detection: Reads Windows registry to detect user’s theme preference
- Native rendering: Uses proper dark mode colors for dialogs and controls
- Fallback support: Works on older Windows versions without dark mode
Enhanced Interactive Preview
The preview system has been significantly improved:
- Clickable variations: Click any preview to apply those settings instantly
- Original reset: Click the original image to reset both sliders to minimum
- Centered captions: Better readability with centered, light gray labels
- Real-time updates: Smooth, responsive preview rendering
Resizable Dialog Window
The main dialog is now fully resizable, allowing you to:
- Expand the preview for better detail inspection
- Fit the dialog to your screen size
- Maintain aspect ratio of preview images
📚 Comprehensive Documentation
This release includes extensive documentation in multiple formats:
README.md (User Guide)
- Complete installation and usage instructions
- Parameter guidelines and recommendations
- Use cases and troubleshooting
- Performance characteristics and benchmarks
API_REFERENCE.md (Developer Guide)
- Detailed class documentation
- Method signatures and descriptions
- Complete code examples
- Thread safety guidelines
- Performance tips
DOCUMENTATION_GUIDE.md
- How to navigate and use all documentation
- Quick reference cards
- Common questions and answers
- IDE integration tips
🎓 Use Cases
AltaLux 1.9.1 excels at:
Photography
- Backlit subjects: Reveal detail in shadows without blowing highlights
- Night photography: Bring out hidden detail in dark areas
- HDR-like effects: Single-image enhancement without tone mapping artifacts
Document Processing
- Scanned documents: Improve readability of faded or poorly-lit scans
- Historical photos: Enhance detail while preserving authenticity
- Technical drawings: Improve contrast in fine details
Professional Applications
- Medical imaging: Enhance tissue detail without amplifying noise
- Surveillance footage: Improve visibility in low-light conditions
- Scientific imaging: Reveal subtle features in microscopy
🚀 Migration Guide
For Users
No action required! Simply replace your old AltaLux.dll with the new version:
- Download the new DLL
- Copy to IrfanView’s
Pluginsfolder - Restart IrfanView
Your existing settings in the INI file will be preserved and continue working.
For Developers
Breaking change: The color preservation algorithm has changed. If you were using AltaLux programmatically via the IrfanView plugin API:
- Expected behavior change: Colors will now be preserved more accurately
- No API changes: Same function signatures and parameters
- No code changes needed: Drop-in replacement
🙏 Acknowledgments
Special thanks to:
- Karel Zuiderveld for the original CLAHE algorithm
- Irfan Skiljan for IrfanView and the plugin architecture
- The community for feedback, testing, and bug reports
- Contributors who identified issues and suggested improvements
📥 Download
Latest Release: AltaLux v1.9.1.92
Requirements:
- IrfanView 4.50 or later
- Windows 7 or later
- 32-bit or 64-bit (match your IrfanView installation)
📝 Full Changelog
Added
- Comprehensive documentation (README, API_REFERENCE, DOCUMENTATION_GUIDE)
- Native dark mode support for Windows 10/11
- Lookup table optimization for color scaling (1.8-2.5× speedup)
- Early-exit optimization for disabled filter
- Memory alignment (16-byte) for all buffers
- Resizable dialog window
- Clickable preview variations
Fixed
- Corrected color preservation algorithm (multiplicative vs additive)
- Race condition in lookup table initialization
- All compiler warnings (C4244, C4101, C4996, C4018, C4267)
- Misleading exception handling around _aligned_free/_aligned_malloc
- Preview image caption alignment and readability
Changed
- Improved code comments and inline documentation
- Updated GUI with centered captions and better layout
Performance
- 14-20% overall speedup from lookup table optimization
- Eliminated per-pixel division in color injection
- Reduced cache misses with aligned memory allocation
Documentation
- 2,000+ lines of technical documentation
- Complete API reference
- Installation and usage guides
- Troubleshooting section
- Performance tuning guide
📞 Support
Need help? Check the comprehensive documentation in README.md
Want to contribute? See the Development section in README.md
📄 License
Microsoft Public License (MS-PL)
Free for commercial and personal use. See source files for full license text.
