Packing circles inside a shape

Posted by: christian on 5 Jun 2019

(4 comments)

A previous blog post dealt with packing circles into a circle. To fill an arbitrary shape, a slightly different approach is needed. The code presented in my github repo.

A black-and-white PNG image should provided (the black areas to be filled). The ShapeFill class is initialized with its filename, the number of circles (n), and rho_min and rho_max, the ratios of the minimum and maximum circle size to the shortest dimension of the image (defaults are used if these parameters are not provided).

The colours are set at random from a sequence of indexes into a list of CSS-style colour specifiers. Not all the colours need to be set in a single pass through the make_circles algorithm in building an image, but they should all be sent to the ShapeFill constructor in order to set the CSS styles correctly.

# Land colours, sea colours.
c1 = ['#b6950c', '#9d150b']
c2 = ['#173f5f', '#20639b', '#3caea3']

# First fill the land silhouette.
shape = ShapeFill('uk.png', n=3000, rho_max=0.01, colours=c1+c2)
shape.guard = 1000
shape.make_circles(c_idx=range(len(c1)))
shape.make_svg('uk-1.svg')

The UK filled with circles

We can then go round again and pass another image (e.g. the inverse of the original image, to fill in the background):

# Now load the image again, invert it and fill the sea with circles.
shape.read_image('uk.png')
shape.img = 255 - shape.img
shape.n = 5000
shape.make_circles(c_idx=[len(c1)+i for i in range(len(c2))])
shape.make_svg('uk-2.svg')

The UK and surrounding sea filled with circles

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Ken Flerlage 10 months, 3 weeks ago

Really cool stuff. I'm trying to do something just like this except using data to drive the size of the circles--like a typical packed bubble chart, except inside of a shape. Going to dig into your code to see if that might be doable. Thanks!

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christian 10 months, 3 weeks ago

I'm glad you find it interesting. Hope your project works out!
Christian

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Zhuldyz 2 months, 2 weeks ago

Can I put set it up to make two different specific shapes that do not vary like in this example? Thank you for making this! It is really helpful.

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christian 2 months, 2 weeks ago

I'm not sure I understand: you can use any file in place of uk.png as the silhouette that is filled, but the filling shapes used have to be circles.

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