Make RLE or Masks from Bounding Boxes

[Ahmed-G-ElTaher]

Direct Conversion from Bounding Boxes to RLE/Masks

This PR adds functionality to directly convert bounding boxes to RLE format or binary masks without requiring segmentation data.

Implementation

The enhancement modifies the annToRLE method in coco.py to:

• Check if a bbox field exists when no segmentation field is provided
• Use bounding box coordinates to create an RLE representation of the rectangular region
• Maintain backward compatibility with original functionality

This allows the existing annToMask method to work with bounding box annotations automatically, as it relies on annToRLE for the conversion process.

Benefits

• Simplifies workflow: No need to manually convert bounding boxes to masks
• Works with existing COCO API methods that use RLE or masks
• Original functionality is unaffected
• Provides a standardized way to convert from bounding boxes to masks

Testing

Tested with:

• Annotations containing only bounding boxes
• Mixed datasets with both segmentation and bbox-only annotations
• Various COCO API operations that require masks

[Ahmed-G-ElTaher]

@tylin
Can you check this PR ?