Extract data from annotated images

To extract data from annotated images, you need to follow a few key steps depending on the type of annotation and the nature of the data. Here’s a general process:

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1. Identify the Type of Annotation

Annotations can vary:

• Bounding Boxes (e.g., around objects)

• Polygons/Masks (for segmentation)

• Keypoints (for poses or landmarks)

• Text Labels (names, categories)

• Overlaid Text/Arrows (for instruction or context)

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2. Choose the Right Tools

Depending on what you need:

A. For Text Annotations (OCR):

Use Optical Character Recognition (OCR) tools:

• Tesseract OCR (open-source)

• EasyOCR (deep learning-based)

• Google Vision API (cloud-based)

• Amazon Textract

B. For Structured Annotation Files (e.g., COCO, Pascal VOC):

If annotations are stored in separate JSON or XML files:

• Parse using Python:

  • json for COCO

  • xml.etree.ElementTree for Pascal VOC

C. For Embedded/Visual Overlays:

If annotations are directly drawn on the image:

• Use image processing libraries:

  • OpenCV (detect shapes, text, or colors)

  • Pytesseract (to read overlaid text)

  • Image segmentation models if regions are marked

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3. Sample Python Code (OCR with Pytesseract)

python
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import cv2
import pytesseract

# Load image
image = cv2.imread('annotated_image.jpg')

# Preprocess (grayscale, threshold)
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
thresh = cv2.threshold(gray, 150, 255, cv2.THRESH_BINARY)[1]

# OCR
text = pytesseract.image_to_string(thresh)

print("Extracted Text:")
print(text)

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4. For Shape-Based Annotations

Use OpenCV to detect:

• Contours: For boxes, circles, or polygons

• Colors: Identify annotations by specific color

• Coordinates: Use contour bounding rectangles

python
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contours, _ = cv2.findContours(thresh, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
for cnt in contours:
    x, y, w, h = cv2.boundingRect(cnt)
    print(f"Found annotation at: x={x}, y={y}, width={w}, height={h}")

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5. Export Extracted Data

Export to:

• CSV

• JSON

• Pandas DataFrame

Example (export to CSV):

python
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import pandas as pd

data = [{'x': x, 'y': y, 'width': w, 'height': h}]
df = pd.DataFrame(data)
df.to_csv('annotations.csv', index=False)

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If you have specific annotated images you’d like analyzed, you can upload one here and I’ll walk you through extracting the data.