PyTurbopnG 1.4.1

A Python wrapper of libjpeg-turbo for decoding and encoding JPEG image.

PyTurbopnG

A Python wrapper of libjpeg-turbo for decoding and encoding JPEG image.

Prerequisites

• libjpeg-turbo
• numpy

Example

import cv2
from turbojpeg import TurboJPEG, TJPF_GRAY, TJSAMP_GRAY, TJFLAG_PROGRESSIVE

# specifying library path explicitly
# jpeg = TurboJPEG(r'D:\turbojpeg.dll')
# jpeg = TurboJPEG('/usr/lib64/libturbojpeg.so')
# jpeg = TurboJPEG('/usr/local/lib/libturbojpeg.dylib')

# using default library installation
jpeg = TurboJPEG()

# decoding input.jpg to BGR array
in_file = open('input.jpg', 'rb')
bgr_array = jpeg.decode(in_file.read())
in_file.close()
cv2.imshow('bgr_array', bgr_array)
cv2.waitKey(0)

# direct rescaling 1/2 while decoding input.jpg to BGR array
in_file = open('input.jpg', 'rb')
bgr_array_half = jpeg.decode(in_file.read(), scaling_factor=(1, 2))
in_file.close()
cv2.imshow('bgr_array_half', bgr_array_half)
cv2.waitKey(0)

# decoding JPEG image properties
in_file = open('input.jpg', 'rb')
(width, height, jpeg_subsample, jpeg_colorspace) = jpeg.decode_header(in_file.read())
in_file.close()

# encoding BGR array to output.jpg with default settings.
out_file = open('output.jpg', 'wb')
out_file.write(jpeg.encode(bgr_array))
out_file.close()

# encoding BGR array to output.jpg with TJSAMP_GRAY subsample.
out_file = open('output_gray.jpg', 'wb')
out_file.write(jpeg.encode(bgr_array, jpeg_subsample=TJSAMP_GRAY))
out_file.close()

# encoding BGR array to output.jpg with quality level 50. 
out_file = open('output_quality_50.jpg', 'wb')
out_file.write(jpeg.encode(bgr_array, quality=50))
out_file.close()

# encoding BGR array to output.jpg with quality level 100 and progressive entropy coding.
out_file = open('output_quality_100_progressive.jpg', 'wb')
out_file.write(jpeg.encode(bgr_array, quality=100, flags=TJFLAG_PROGRESSIVE))
out_file.close()

# decoding input.jpg to grayscale array
in_file = open('input.jpg', 'rb')
gray_array = jpeg.decode(in_file.read(), pixel_format=TJPF_GRAY)
in_file.close()
cv2.imshow('gray_array', gray_array)
cv2.waitKey(0)

# scale with quality but leaves out the color conversion step
in_file = open('input.jpg', 'rb')
out_file = open('scaled_output.jpg', 'wb')
out_file.write(jpeg.scale_with_quality(in_file.read(), scaling_factor=(1, 4), quality=70))
out_file.close()
in_file.close()

# lossless crop image
out_file = open('lossless_cropped_output.jpg', 'wb')
out_file.write(jpeg.crop(open('input.jpg', 'rb').read(), 8, 8, 320, 240))
out_file.close()

Installation

macOS

• brew install jpeg-turbo
• pip install -U git+git://github.com/lilohuang/PyTurbopnG.git

Windows

• Download libjpeg-turbo official installer
• pip install -U git+git://github.com/lilohuang/PyTurbopnG.git

Linux

• RHEL/CentOS/Fedora

  • Download libjpeg-turbo.repo to /etc/yum.repos.d/
  • sudo yum install libjpeg-turbo-official
  • pip install -U git+git://github.com/lilohuang/PyTurbopnG.git

• Ubuntu

  • sudo apt-get update
  • sudo apt-get install libturbojpeg
  • pip install -U git+git://github.com/lilohuang/PyTurbopnG.git

Benchmark

macOS

• macOS Sierra 10.12.6
• Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
• opencv-python 3.4.0.12 (pre-built)
• turbo-jpeg 1.5.3 (pre-built)

Function	Wall-clock time
cv2.imdecode()	0.528 sec
TurboJPEG.decode()	0.191 sec
cv2.imencode()	0.875 sec
TurboJPEG.encode()	0.176 sec

Windows

• Windows 7 Ultimate 64-bit
• Intel(R) Xeon(R) E3-1276 v3 CPU @ 3.60 GHz
• opencv-python 3.4.0.12 (pre-built)
• turbo-jpeg 1.5.3 (pre-built)

Function	Wall-clock time
cv2.imdecode()	0.358 sec
TurboJPEG.decode()	0.135 sec
cv2.imencode()	0.581 sec
TurboJPEG.encode()	0.140 sec