docker-jpegprogs

JPG/JPEG image optimization/manipulation via libjpeg-progs within Docker

Pull image

$ docker pull buffcode/docker-jpegprogs

Source directory

This image creates a volume at /source, so you can mount a local directory to this remote directory and access any file within. Please note that jpegtran will not overwrite the input file but output the optimized image to STDOUT. As an alternative you can use the the -outfile <filename> argument with the same path to overwrite the input file.

Contained applications

This image makes use of the libjpeg-progs package. As such it also other tools like exifautotran, jpegexiforient, rdjpgcom, wrjpgcom, cjpeg and djpeg.

Running jpegtran

$ docker run buffcode/docker-jpegprogs --help
usage: /usr/bin/jpegtran [switches] [inputfile]
Switches (names may be abbreviated):
  -copy none     Copy no extra markers from source file
  -copy comments Copy only comment markers (default)
  -copy all      Copy all extra markers
  -optimize      Optimize Huffman table (smaller file, but slow compression)
  -progressive   Create progressive JPEG file
Switches for modifying the image:
  -crop WxH+X+Y  Crop to a rectangular subarea
  -grayscale     Reduce to grayscale (omit color data)
  -flip [horizontal|vertical]  Mirror image (left-right or top-bottom)
  -perfect       Fail if there is non-transformable edge blocks
  -rotate [90|180|270]         Rotate image (degrees clockwise)
  -transpose     Transpose image
  -transverse    Transverse transpose image
  -trim          Drop non-transformable edge blocks
Switches for advanced users:
  -arithmetic    Use arithmetic coding
  -restart N     Set restart interval in rows, or in blocks with B
  -maxmemory N   Maximum memory to use (in kbytes)
  -outfile name  Specify name for output file
  -verbose  or  -debug   Emit debug output
Switches for wizards:
  -scans file    Create multi-scan JPEG per script file

Optimize a single image

# output to new file
$ docker run -v /local-path-to-image:/source buffcode/docker-jpegprogs \
    -optimize -copy none image.jpg >image-optimized.jpg

# overwrite input file
$ docker run -v /local-path-to-image:/source buffcode/docker-jpegprogs \
    -optimize -copy none -outfile image.jpg image.jpg

Recursivley optimize all images

The following command finds all images in the current folder (find...), mounts it to the Docker volume (-v ...) and optimizes the image (-optimize -copy none).

$ find . -name "*.jpg" | \
    xargs -I{} docker run -v `pwd`:/source buffcode/docker-jpegprogs \
    -optimize -copy none -outfile {} {}

Run another tool

In case you would like to run another tool than jpegtran eg. exifautotran use the following command:

$ docker run --entrypoint '/usr/bin/exifautotran' buffcode/docker-jpegprogs --help
exifautotran [list of files]

Transforms Exif files so that Orientation becomes 1