Can Google Vision API be applied to detecting and labelling objects with pillow Python library in videos rather than in images?

/ / Published in Artificial Intelligence, EITC/AI/GVAPI Google Vision API, Understanding shapes and objects, Drawing object borders using pillow python library

The query regarding the applicability of Google Vision API in conjunction with the Pillow Python library for object detection and labeling in videos, rather than images, opens up a discussion that is rich with technical details and practical considerations. This exploration will consider the capabilities of Google Vision API, the functionality of the Pillow library, and how these can be orchestrated to handle video content for object detection and labeling tasks.

Google Vision API Overview

Google Vision API is a powerful tool provided by Google Cloud that enables developers to integrate vision detection features including image labeling, face and landmark detection, optical character recognition (OCR), and more into applications. The API uses machine learning models to process images and understand their content without any manual tagging. The primary focus of the API is on images; however, it does not natively support video files. This means that direct processing of video files to detect and label objects is not straightforwardly supported by the API.

Pillow Python Library Overview

Pillow is an open-source Python Imaging Library that adds support for opening, manipulating, and saving many different image file formats. It is designed to handle raster-based image processing. Pillow can be used for basic image operations like resizing, cropping, rotating, and more, as well as more complex tasks such as image filtering, conversion between formats, and image enhancement.

Adapting Google Vision API for Video Processing

Since Google Vision API does not directly accept video files, the first step in processing videos for object detection and labeling is extracting frames from the video. Each frame of a video is essentially an image; thus, once you have the frames, you can use Google Vision API to analyze these images.

Extracting Frames from Videos

To extract frames from videos, you would typically use a library that can handle video operations, such as OpenCV or FFmpeg. However, since our focus includes the use of the Pillow library, it's important to note that Pillow alone cannot extract frames from videos as it does not support video processing directly. Thus, you would need to integrate it with a video processing library.

Example using OpenCV to extract frames:

python
import cv2

# Open video file
cap = cv2.VideoCapture('path_to_video.mp4')

frameRate = cap.get(5) # Get frame rate

while(cap.isOpened()):
    frameId = cap.get(1) # Get current frame number
    ret, frame = cap.read()
    if (ret != True):
        break
    if (frameId % math.floor(frameRate) == 0):
        filename = "frame%d.jpg" % count;count+=1
        cv2.imwrite(filename, frame)

cap.release()

Processing Frames with Google Vision API

Once frames are extracted and saved as images, you can use Google Vision API to detect and label objects in each frame. Here’s a simplified example of how to use the Vision API with Python:

python
from google.cloud import vision
import io

client = vision.ImageAnnotatorClient()

with io.open('path_to_frame.jpg', 'rb') as image_file:
    content = image_file.read()

image = vision.Image(content=content)
response = client.object_localization(image=image)
objects = response.localized_object_annotations

for object_ in objects:
    print('n{} (confidence: {})'.format(object_.name, object_.score))
    print('Normalized bounding polygon vertices: ')
    for vertex in object_.bounding_poly.normalized_vertices:
        print(' - ({}, {})'.format(vertex.x, vertex.y))

Labeling and Drawing Borders Using Pillow

After detecting objects using Google Vision API, you can use Pillow to draw borders around detected objects on the frames. Here’s how you might do it:

python
from PIL import Image, ImageDraw

image_path = 'path_to_frame.jpg'
image = Image.open(image_path)
draw = ImageDraw.Draw(image)

# Assuming `objects` is the list of objects detected by Vision API
for object_ in objects:
    box = [(vertex.x * image.width, vertex.y * image.height) for vertex in object_.bounding_poly.normalized_vertices]
    draw.line(box + [box[0]], width=5, fill='#00ff00')

image.save('path_to_output_frame.jpg')

Final Thoughts

This approach, while effective, requires handling each video frame as a separate image, which can be computationally intensive and time-consuming, especially for videos with a high frame rate or long duration. Optimization strategies such as selecting key frames (frames at regular intervals) rather than processing every single frame, can be important in making the process more efficient.

This detailed exploration underscores the adaptability of Google Vision API and the Pillow library to extend beyond their primary capabilities, demonstrating a versatile approach to video processing for object detection and labeling tasks.

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