Posts Tagged ‘photo’

convertconditional: convert an image if it fulfills certain conditions

August 28, 2013 Leave a comment

Recently I needed a script to batch convert only those images amongst a large amount of images which fulfil certain criteria, namely of being exactly of a stated size. The script is based on ImageMagick’s convert and basically takes an arbitrary amount of convert parameters. I personally use this script to automatically reduce size and quality of photos taken with a specific camera in order to reduce their hard disk space coverage.

The script

#! /usr/bin/python
# convertconditional: Convert an image if it fulfills certain conditions, e.g. is of a certain size. Requires ImageMagick's convert.
# Rainhard Findling 2013/08
# example to convert all *JPG within the current directory with are of certain size to a reduced size and quality:
# find . -iname "*JPG" -exec ./convertconditional {} -filtersize 3888x2592 -convertparams "-resize 3500x3000 +repage -quality 80" \;
import argparse # check for help
import subprocess
import sys
# specify arguments
parser = argparse.ArgumentParser()
parser.add_argument('inputfile', help='path to the file that will be converted.')
parser.add_argument('-convertparams', required=True, help='parameters handed to the convert command used internally, e.g. resize, repage, reduce quality etc. Example: "-resize 300x200 +replage -quality 92"')
parser.add_argument('-filtersize', help='only convert if original image is of this size, stated as WIDTHxHEIGHT, e.g. 3500x3200.')
parser.add_argument('-o', '--outputfile', help='path to where the converted image will be stored. if not specified, the original file will be overwritten.')
parser.add_argument('-v','--verbose',help='print verbose output.',action='store_true')
args = parser.parse_args()
# make sure we can process names with spaces
args.inputfile = '"' + args.inputfile + '"'
# check for correct arguments
if not args.outputfile:
args.outputfile = args.inputfile
if args.filtersize:
filter_x = int(args.filtersize.split('x')[0])
filter_y = int(args.filtersize.split('x')[1])
if args.verbose:
print 'inputfile=' + args.inputfile
print 'outputfile=' + args.outputfile
if args.filtersize:
print 'resizing only', str(filter_x) + 'x' + str(filter_y), 'images.'
print 'convertparams=' + args.convertparams
# get size of image
imagesize = subprocess.check_output(["identify -format '%wx%h' '" + args.inputfile + "'"],
imagesize_x = int(imagesize.split('x')[0])
imagesize_y = int(imagesize.split('x')[1])
# condition: filter for images of certain size
if args.filtersize:
if args.verbose:
print 'size of', args.inputfile, 'is', str(imagesize_x) + "x" + str(imagesize_y)
# check filter criteria
if not imagesize_x == filter_x or not imagesize_y == filter_y:
print 'leaving out ' + args.inputfile + ' as it is of size ' +  str(imagesize_x) + "x" + str(imagesize_y) + " (required: " + args.filtersize + ")"
# passed all conditions: convert image
print 'converting ' + args.inputfile + ' (size: ' +  str(imagesize_x) + "x" + str(imagesize_y) + ')'
# convert image
command="convert '" + args.inputfile + "' " + args.convertparams + " '" + args.outputfile + "'"
if args.verbose:
print 'command:', command
imagesize = subprocess.check_output([command],

The script is written in Python, so all you need to do is save it (e.g. in a file called “convertconditional”) and make it executable:

chmod +x convertconditional

Then you can either call it with stating it’s path (e.g. “./convertconditional [parameters]”), or add it to your systems PATH to call it from everyhwere.

Script execution

In order to convert input.jpg to output.jpg, you can try

convertconditional input.jpg -filtersize 3888x2592 -convertparams "-resize 3500x3000 +repage -quality 85" -o output.jpg
  • -filtersize optional filtering: only convert the image  in case it is exactly of the stated size
  • -convertparams states parameters which should be handed to ImageMagick’s convert
  • -o states where to store the converted image (original image gets overwritten if omitted)

In case you want to conditionally convert multiple files (as with my usecase) you can combine convertconditional with find and overwrite the original files:

find . -iname "*JPG" -exec convertconditional {} -filtersize 3888x2592 -convertparams "-resize 3800x +repage -quality 85" \;

Batch panorama stitching with review using Hugin

June 7, 2013 1 comment
Panorama of Mount Batur, Bali, Indonesia.

Panorama of Mount Batur, Bali, Indonesia.

Stitching images to a panorama may take it’s time — which might be frustrating in case you need to create a whole lot of panoramas. Hugin can save you a lot of time here. Basics of Hugin in a nutshell: it’s is a panorama tool providing a command line interface+UI and a two phased processing. Initially, you create a Hugin project which holds links to several images (.pto-file). Then you first sent your photos to the “assistant queue” which performs a preliminary stitching, which you can review and correct if necessary. Second, you send your images + rough stitching info to the “stitching queue”, which does the actual high quality stitching for you. Hugin further provides a batch processor which basically holds a list of Hugin projects — this is what we’re going to make use of.


To semi-automatically stitch all your panoramas at once, including a review of preliminary stitched panoramas, you can do the following:

  1. Move all photos that should be part of the same panorama to a separate folder — for each panorama you should have a separate folder then. This is the only step you actually have to do by hand completely. We assume you create the folders with leading zeros:
    for i in {001..100}; do mkdir $i; done
  2. Assuming that all these folders are located inside the same parent folder and you are in this parent folder, use Hugin’s “pto_gen” command to automatically generate the Hugin projects (.pto-files, make sure to adjust the image extension so that it fits your needs):
    for d in `ls`; do pto_gen $d/*.jpg; done

    If you happen to have multiple such folders, each containing multiple panorama folders, you can generate all panorama files at once using the following command instead (assuming all these folders have been named “pano”):

    for d in `find . -name "pano"`
        for p in `ls $d`
            do pto_gen $d/$p/*jpg
  3. Add all these projects to the Hugin Batch Processor assistant queue:
    find . -name "*pto" -exec PTBatcherGUI -a {} \;
  4. Let the assistant queue create your preliminary panoramas
  5. Optionally review and correct each panorama using Hugin itself:
    find . -name "*pto" -exec hugin {} \;

    Sometimes it can be helpful to just review a bunch of panoramas at once instead:

    for d in `ls -d * | egrep "00[0-9]{1}"` # for panorama 000-009, adapt for your use
        hugin $d/*.pto
  6. Add the projects to the Hugin Batch Processor stitching queue:
    find . -name "*pto" -exec PTBatcherGUI {} \;
  7.  Let the stitching queue create all panoramas.

The following snippet converts panoramas generated as tifs into jpgs and moves them back to their original location (amongst other pictures) using convert from ImageMagick:

find . -name "*tif" -exec rename "s/ //g" {} \; # remove tif filename whitespaces added by Hugin

for t in `find . -name "*tif"`
    tif_path=`dirname $t`
    new_name=`basename $t | sed "s/tif/jpg/"`
    new_path=$tif_path/../../$new_name # we want to have panoramas amongst other pictures
    convert $t $new_path

Finally, if you’re pleased with your panoramas you can delete all tifs generated on the way:

find . -name "*tif" -delete

If you’d like to keep the original pictures used to create panoramas, but would like to share all other pictures anyway, here’s the command to copy all files but omit all “pano” folders inside:

for f in `find . -type f`
    if [ ! `echo $f | grep "/pano/"` ]
        # is not a pano folder and not a file inside a pano folder
        cp --verbose --parents "$f" "$DEST"

Installating Hugin on Ubuntu 12.04

When installing Hugin from the Ubuntu repositories in Ubuntu 12.04, unfortunately pto_gen is missing (seems to be fixed for 14.04 and newer). Therefore install Hugin from the Hugin repository as stated in their Ubuntu howto:

sudo add-apt-repository ppa:hugin/hugin-builds
sudo apt-get update
sudo apt-get install hugin enblend panini