Movie DNA

Update: A follow-up of this post has a script that can do the montage part the job much faster than ImageMagick.

Brendan Dawes has this interesting idea he calls Cinema Redux. A entire film is distilled down to a single image. You take one frame from each second of the movie, shrink that frame down to 8x6 pixels, then line them up in a montage with 60 frames per row. Each row then represents one minute of film. There are 8 examples on his website.

I was interested in trying this for myself, but I couldn’t find any of his code, which he had written in Java, to do it myself. Then it hit me: I really don’t need to write anything to do this! Here is how you can make your own using only two tools: mplayer and ImageMagick.

Originally I thought that I may need to write a small Perl script to glue these two things together, but found, after digging though man pages, that this was completely unnecessary. There are two steps involved and each tool does one step: grab all of the frames, and second, make a montage out of those frames. Grabbing the frames is one call to mplayer,

mplayer -vo jpeg:outdir=frames -ao dummy -vf framestep=30,scale=8:6 \

What we are doing here is dumping every 30th frame (assuming 30 frames-per-second) into a directory named frames. These images will be named by consecutive 8-digit numbers. These frames are also resized down to 8x6 pixels. If you are converting a video with a different aspect ratio, such as a wide-screen movie without letter-boxing, you will need to adjust this. A wide-screen film would be 16x9.

Next, we glue these frames together with ImageMagick,

montage -geometry +0+0 -background black -tile 60x "frames/*jpg" \

This will create the montage in the file montage.jpg . There is something important to note here. See how the file glob is quoted so that the shell will not expand it? Thats because listing 7000 frames pushes the limits of the system in passing command line arguments. ImageMagick knows about file globs and will do this internally.

And that’s it! I put these together into that handy shell script that will also remove the frames after the montage has been successfully created. The process takes between 6 and 12 hours, depending on the length of the movie. It takes the movie running time to produce all the frames file, then it spends the rest of the time creating the montage, which is disappointingly slow. (Maybe I could write a Perl script that does it faster?) The script will create a montage out of just about any video you throw at it, thanks to mplayer. Example usage for DVDs,

$ ./ dvd://

I did it on three movies so far: Gladiator, Tron, and The Matrix. I did it to Tron and The Matrix because I wanted to see if these movies have a dominant color scheme.

To inspect the coloring of these films, I took a hue histogram. Tron is very obvious: lots of blues and cyans dominate,

I was expecting to see a lot of green show up in The Matrix, but was a little bit disappointed,

To get these histograms, I loaded the images into GNU Octave, converted it to HSV so that the red channel is really the hue channel. Then I had the GIMP make the histograms by providing the histogram of the “red” (read hue) channel. I dropped an HSV color bar below with some image editing.

octave> m = imread("movie.jpg");
octave> [x map] = rgb2ind(m);
octave> map = rgb2hsv(map);
octave> imwrite("movie-hsv.jpg", x, map);

See if you can find some really interesting things to do with this.

blog comments powered by Disqus

null program

Chris Wellons