README.md

jpeg reader

Pure python jpeg reader.

Developed with Python 3.8, but should be compatible with Python 3.6+.

What this module is

This will get resolution, pixel aspect ratio, and some metadata from most JPEG files. Additionally, byte offsets to known segment markers are stored.

What this module isn't

While JPEG files conform to a standard, there are a vast number of application-specific formats for image metadata and thumbnails. Therefore, this module won't read all metadata from each and every type of JPEG. That's a rabbit hole I don't care to go down.

Usage

jpeg_reader can be imported and used as a module to extract information from a JPEG file.

# Example: Print file info
from jpeg_reader import JpegFile


jf = JpegFile("test_image.jpg")
print(jf.resolution)
print(jf.pixel_aspect)
for key, value in jf.metadata.items():
    print(key, value)

# Example: Read SOS (Start of Scan) data
from jpeg_reader import JpegFile
from jpeg_reader import ReadSegment
from jpeg_reader import segment_markers


jf = JpegFile("test_image.jpg")
for segment in jf.segments:
    marker = segment.marker
    if segment.marker == segment_markers.SOS:
        sos_segment = segment
        break

with open("test_image.jpg", 'rb') as f:
    with ReadSegment(file=f, segment_start=sos_segment.offset) as seg:
        seg.go_to_segment_data()
        # Do whatever you need to here
        pass

jpeg_reader.py can also be used from the command line to print information about an individual file, or a directory containing multiple images.

jpeg_reader.py test_image.jpg

jpeg_reader.py C:\path\to\images

Handy links:

These are links that I found useful for reference.

JPEG:

• Specs: https://www.w3.org/Graphics/JPEG/itu-t81.pdf
• https://en.wikipedia.org/wiki/JPEG#Syntax_and_structure

APP Segments:

• http://www.ozhiker.com/electronics/pjmt/jpeg_info/app_segments.html

JFIF:

• Specs: http://www.ecma-international.org/publications/files/ECMA-TR/ECMA%20TR-098.pdf
• http://vip.sugovica.hu/Sardi/kepnezo/JPEG%20File%20Layout%20and%20Format.htm
• https://en.wikipedia.org/wiki/JPEG_File_Interchange_Format#File_format_structure

EXIF:

• Specs: https://www.exif.org/Exif2-2.PDF
• https://www.media.mit.edu/pia/Research/deepview/exif.html