mosaic4 bottom left image fix

[haoyuefan]

fix a bug in load_mosaic

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Improved image stitching for data augmentation in YOLOv5.

📊 Key Changes

• Adjusted the calculation when stitching images together in the bottom left mosaic quadrant.

🎯 Purpose & Impact

• 🎨 Purpose: This change ensures that when images are combined to create a mosaic for training the YOLOv5 model, the bottom left image is correctly positioned without any overlap or gap.
• ✅ Impact: The potential impact is an increase in the accuracy of the YOLOv5 model by using better-formed training data, leading to improved performance in object detection tasks.

[github-actions]

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[glenn-jocher]

@yuefanhao yes I think you are right, this change to the bottom left x coordinates would match the values used for the top left x coordinates.

Did you see any actual incorrect training images before this fix?