Join GitHub today
GitHub is home to over 28 million developers working together to host and review code, manage projects, and build software together.Sign up
Creates ghostly, impressionistic artworks using a Monte Carlo algorithm that converges toward a target image.
Fetching latest commit…
Cannot retrieve the latest commit at this time.
|Type||Name||Latest commit message||Commit time|
|Failed to load latest commit information.|
RECTIFY(1) General Commands Manual RECTIFY(1) NAME rectify - converge towards a target image using a Monte Carlo algo‐ rithm. SYNOPSIS rectify [IMAGE] rectify [IMAGE] [options] DESCRIPTION Rectify is a command-line tool that uses a Monte Carlo (MC) algorithm to converge towards a target image using a random sequence of rectangu‐ lar brush strokes. Images produced by rectify have a ghostly, impres‐ sionistic quality. Rectify works by repeatedly attempting to apply a randomly placed black or white brush strokes of rectangular shape to a canvas. The stroke is blended with the existing pixel block on the canvas and the change is accepted with a Boltzmann weight that accounts for the difference in the absolute value of the pixel block's distance from the target image following the trial move. The system is coupled to a thermal bath which allows the user to control the probability of accepting moves that take the image away from the target, thus allowing the rate of convergence to be tuned. Rectify avoids unneccessary dependency on zlib and libpng by using LodePNG to decode and encode PNG images. MersenneTwister is used to provide high quality and efficient random numbers. Rectify must be passed at least one command-line argument, the path of a PNG IMAGE file to be used as the target image. The image will auto‐ matically be converted to grayscale if color is detected. When run, rectify will output a sequence of images showing the evolution of the canvas towards the target image. In addition, the current acceptance rate is printed to stdout allowing the user to monitor the rate of con‐ vergence. Rectify is trivially parellelizable, MPI support will follow (allowing efficient processing of very large images). OPTIONS rectify supports the following short- and long-form command-line options. Invoking rectify with no options will print a help message. -h, --help Print the help message. -i INT, --iterations INT Where INT is an integer specifying the number of MC iterations. -f INT, --frames INT Where INT is an integer specifying the number of frames to be saved. -s DOUBLE, --stroke DOUBLE Set the maximum extent of the trial stroke, where DOUBLE indi‐ cates the stroke extent as a fraction of the target image width, e.g. a value of 0.5 would set the maximum stroke extent (both width and height) to half the width of the target image. The algorithm proceeds more slowly when the maximum stroke width is large since, on average, more pixels must be processed per trial move. -c IMAGE, --canvas IMAGE Start the algorithm using an existing canvas given by PNG IMAGE file. The IMAGE must be the same size as the target otherwise rectify will abort. If the IMAGE is full color it will be con‐ verted to grayscale before the algorithm starts. This option can also be used to continue covergence from an existing rectify project, e.g. if too few iterations were chosen. -t DOUBLE, --temperature DOUBLE Specify the temperature of the thermal bath. A higher tempera‐ ture will mean that more trial brush strokes are accepted. At zero temperature, only moves that take the canvas closer to the target will be accepted (comparable to a hill climbing algo‐ rithm). Temperature adds noise to the system and can be used to tune the rate of convergence as well as the style of image pro‐ duced. -l, --log Use logarithmic spacing for sampling points. This is useful when convergence is very slow. -d DIRECTORY, --directory DIRECTORY Specify a directory for the output files. DIRECTORY should be in the working directory and will be created if it doesn't already exist. -m, --monitor Turn on acceptance monitoring. If set, rectify will monitor sta‐ tistics for the acceptance rate and compute histograms for accepted brush strokes. This is useful for determining what stroke sizes are dominant as the canvas evolves. Trial stroke sizes can be tuned accordingly. In monitor mode, rectify will produce three additional output files: log.txt a log file of the acceptance rate at each sampling time hist.txt the acceptance probability for each stroke size (width, height), and hist_xy.txt a two-dimensional matrix of the histogram data. DEFAULTS iterations 1000000 frames 1000 temperature 0.1 stroke 0.1 logarithmic off monitor off SEE ALSO flux(1) CREDITS LodePNG, http://lodev.org/lodepng. MersenneTwister, www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html. Anna, for the name. BUGS Email bugs, comments, and artwork to firstname.lastname@example.org. Lester Hedges 2013/01/21 RECTIFY(1)