JP2 image metadata copying for cv2 treatment

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Summary

The problem at hand involves preserving metadata from JP2 images when processing them with OpenCV (cv2), which discards metadata by default. The goal is to find a suitable Python module that can extract and reattach metadata for further use in other software that relies on this metadata.

Root Cause

The root cause of this issue lies in the way cv2 handles image metadata:

  • Loss of metadata: cv2, by design, focuses on image processing and does not preserve metadata when reading or writing images.
  • Incompatibility with JP2: The JP2 format, which supports extensive metadata, is not fully compatible with cv2’s metadata handling capabilities.

Why This Happens in Real Systems

This issue occurs in real systems due to:

  • Format limitations: Different image formats have varying levels of support for metadata, leading to compatibility issues when processing images across formats.
  • Library constraints: Image processing libraries like cv2 prioritize image data over metadata, resulting in metadata loss during processing.

Real-World Impact

The impact of this issue includes:

  • Data loss: Critical metadata, such as geolocation or capture time, is lost during image processing, affecting the usability of the images in certain applications.
  • Incompatibility: Images processed with cv2 may not be compatible with software that relies on the presence of specific metadata.

Example or Code (if necessary and relevant)

from glymur import Jp2k
import cv2
import numpy as np

# Open JP2 image with glymur to preserve metadata
jp2 = Jp2k('input.jp2')

# Extract metadata
metadata = jp2.box_xml

# Convert JP2 image to numpy array for cv2 processing
image_data = np.frombuffer(jp2[:], dtype=np.uint8)

# Process image with cv2
image = cv2.imdecode(image_data, cv2.IMREAD_COLOR)

# ... process the image ...

# Save processed image
cv2.imwrite('output.tif', image)

# Reattach metadata using glymur
output_jp2 = Jp2k('output.jp2')
output_jp2.box_xml = metadata

How Senior Engineers Fix It

Senior engineers address this issue by:

  • Using metadata-preserving libraries: Libraries like glymur or gdal can extract and reattach metadata from JP2 images.
  • Implementing custom metadata handling: Engineers may develop custom solutions to extract, store, and reattach metadata during image processing.

Why Juniors Miss It

Junior engineers might overlook this issue due to:

  • Lack of experience: Inexperience with image processing and metadata handling can lead to unawareness of the potential for metadata loss.
  • Insufficient knowledge of library limitations: Not fully understanding the limitations and constraints of libraries like cv2 can result in unexpected metadata loss during image processing.