jpegtran-cffi 0.5.1

Extremly fast, (mostly) lossless JPEG transformations

jpegtran-cffi is a Python package for fast JPEG transformations. Compared to other, more general purpose image processing libraries like wand-py or PIL/Pillow, transformations are generally more than twice as fast (see Benchmarks). In addition, all operations except for scaling are lossless, since the image is not being re-compressed in the process. This is due to the fact that all transformation operations work directly with the JPEG data.

This is achieved by using multiple C routines from the Enlightenment project’s epeg library (for scaling) and jpegtran from the Independent JPEG Group’s libjpeg library (for all other operations). These routines are called from Python through the CFFI module, i.e. no external processes are launched.

The package also includes rudimentary support for getting and setting the EXIF orientation tag, automatically transforming the image according to it and obtaining the JFIF thumbnail image.

jpegtran-cffi was developed as part of a web interface for the spreads project, where a large number of images from digital cameras had to be prepared for display by a Raspberry Pi. With the Pi’s rather slow ARMv6 processor, both Wand and PIL were too slow to be usable.

Requirements

• CPython 2.6, 2.7, 3.3 or PyPy

• cffi

• libjpeg8 with headers (earlier versions will not work)

Installation

$ pip install jpegtran-cffi

Usage

from jpegtran import JPEGImage

img = JPEGImage('image.jpg')

# JPEGImage can also be initialized from a bytestring
blob = requests.get("http://example.com/image.jpg").content
from_blob = JPEGImage(blob=blob)

# Reading various image parameters
print img.width, img.height  # "640 480"
print img.exif_orientation  # "1" (= "normal")

# If present, the JFIF thumbnail can be obtained as a bytestring
thumb = img.exif_thumbnail

# Transforming the image
img.scale(320, 240).save('scaled.jpg')
img.rotate(90).save('rotated.jpg')
img.crop(0, 0, 100, 100).save('cropped.jpg')

# Transformations can be chained
data = (img.scale(320, 240)
            .rotate(90)
            .flip('horizontal')
            .as_blob())

# jpegtran can transform the image automatically according to the EXIF
# orientation tag
photo = JPEGImage(blob=requests.get("http://example.com/photo.jpg").content)
print photo.exif_orientation  # "6" (= 270°)
print photo.width, photo.height # "4320 3240"
corrected = photo.exif_autotransform()
print corrected.exif_orientation  # "1" (= "normal")
print corrected.width, corrected.height  # "3240 4320"

For more details, refer to the API Reference.

Benchmarks

All operations were done on a 3.4GHz i7-3770 with 16GiB of RAM and a 7200rpm HDD with the following 2560x1920 8bit RGB JPEG:

http://upload.wikimedia.org/wikipedia/commons/8/82/Mandel_zoom_05_tail_part.jpg

Both wand-py and PIL were run with the fastest scaling algorithm available, for wand-py this meant using Image.sample instead of Image.resize and for PIL the nearest-neighbour filter was used for the Image.resize call.

Benchmark source: https://gist.github.com/jbaiter/8596064

License

The MIT License (MIT)

Copyright (c) 2014 Johannes Baiter <[e-mail]>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE