Thursday, 10 January 2013

Time to Colour

It is hard to convey time in still images...


... but if colour isn't too important you can make the image black and white, then use colour to convey time.


This method works well where the background doesn't change; the splash of colour resulting from movement on the grey background draws the eye in.


It's easy to create photos like this. The hard bit is actually capturing the picture because you need to make sure the images align well, using a tripod is a good idea! Once you have the pictures aligned neatly then make each one greyscale, then colourise each one. They need to be coloured equally spaced shades of the spectrum in time order from red through the spectrum and back to red. For three images pure red, green and blue work perfectly.

The original pictures...

... and the recoloured pictures.

Using additive blending flatten the stack of images. Parts of the image where nothing moved should add to make shades of grey, but parts where things moved will be colourful.


The effect of movement is really clear if you look at cropped parts of the image where either nothing moves:


... or where there is a lot of movement:


Using a program where you can write scripts to automate processing steps it is very quick to make pictures like this. In ImageJ this macro takes an image stack and generates the recoloured and flattened images:

run("8-bit");
run("RGB Color");
setBatchMode(true);
src=getImageID();
d=nSlices();
for (i=0; i<d; i++) {
setSlice(i+1);
run("Duplicate...", "title=tmp");

run("HSB Stack");
run("Select All");
setSlice(1);
setColor(255*i/d);
fill();
setSlice(2);
setColor(255);
fill();
run("RGB Color");

run("Select All");
run("Copy");
close();
selectImage(src);
run("Paste");
}
setBatchMode(false);
run("Z Project...", "start=1 stop="+nSlices()+" projection=[Sum Slices]");

Really quite simple considering how impressive the results are.


Software used:
ImageJ: Image processing.


2 comments:

  1. Really neat method Richard. My favourite is he last image. Thanks for the ImageJ macro.

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    Replies
    1. No prob, let me know if you ever use it. It'd be cool to see what you create.

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