autosplit: take image files with uppercase extensions into account

[jdfr]

IMG_FORMATS contains lowercase versions of image file extensions.

In all other uses of IMG_FORMATS, care is taken to take into account image files regardless of the extension's case. However, the autosplit() function doesn't: it silently fails to include files whose extensions have any uppercase letter. This is not a problem on Windows, but has bitten me on Linux. This commit fixes the problem.

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Refined image file filtering mechanism in the dataset loading process.

📊 Key Changes

• Altered the file search pattern from '**/.' to '.' to adjust the scope of recursive search.
• Synchronized the commented pathlib-based alternative with the IMG_FORMATS global.
• Ensured the file list is always sorted, improving the consistency of data processing.

🎯 Purpose & Impact

• 🎨 Purpose: To streamline the file discovery process, ensuring that only relevant image files are included in the dataset. The pathlib alternative is kept up-to-date for potential future use.
• 🚀 Impact:
  • Users can expect more reliable dataset loading with a refined search that may improve load times and reduce errors.
  • Consistent sorting of files contributes to reproducibility, important for model training and evaluation tasks.

[github-actions]

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[glenn-jocher]

@jdfr PR is merged. Thank you for your contributions to YOLOv5 🚀 and Vision AI ⭐