Pencil charts for visualising colours

As a result of a discussion with a photographer friend of mine, I’ve been thinking (not for the first time) about visualising the colour palette of images. Consider this sunset, for example (a picture I took in Adelaide 8 years ago):

The photograph is rich in yellow and orange. However, the apparent blue in the sky is actually grey, and the apparent grey of the sea is actually brown. If we postulate a standard set of 35 plausible pencil colours, and map each pixel to the closest-matching pencil colour, we get this (I have done the comparison in RGB space):

Then we can visualise the colour palette of the image by showing the wear on the virtual pencils, if each virtual pencil has been used to colour the corresponding pixels. It can be seen that a lot of orange, brown, and grey was used (click to zoom):

Conversely, this beach scene (photographed in Vanuatu in 2016) is rich in blues:

The warm light greys of the beach don’t quite find an exact match among the pencils, but the other colours match fairly well:

And here is the pencil visualisation (click to zoom):

If, rather than using a standard set of colours, we extract the pencil colours from the image itself (image quantisation), fewer pencils will, of course, be required:

The fit to the original image will be much closer as well:

So this is a trick to remember for another day – pencil visualisations!


Advertisements

Elements in the Human Body

The most common elements in the human body (logarithmic scale, data from Wikipedia, chart produced using R). Yes, we are mostly made of air!


Something different

This picture illustrates the ill-fated expedition to Australia described in H.P. Lovecraft’s horror story The Shadow Out of Time. The images in the montage are edited versions of public-domain pictures, and include this copy of the Necronomicon. The complete image is © Anthony Dekker.

… On July 10, 1934, there was forwarded to me by the Psychological Society the letter which opened the culminating and most horrible phase of the whole mad ordeal. It was postmarked Pilbarra, Western Australia, and bore the signature of one whom I found, upon inquiry, to be a mining engineer of considerable prominence. Enclosed were some very curious snapshots. I will reproduce the text in its entirety, and no reader can fail to understand how tremendous an effect it and the photographs had upon me. …

The “Pilbarra” in this story (and on the map) is presumably Pilbara Road District, an old name for what is now the town of Port Hedland, Western Australia (although the address given by Lovecraft matches a no longer extant street in the nearby ghost town of Cossack). Lovecraft’s story also refers to a precise geographical location: 22° 3′ 14” S, 125° 0′ 39” E. See more on the Australian aspects of the story at Trollunteer. Propnomicon also did some really good props a few years back.


Religion in the Australian Census

Following up on my earlier post, here is a chart of religion in Australia, by age (as per the 2016 Census, with percentages on the vertical axis relating to the population of Australia as a whole, and excluding people with no religion specified). Coloured areas in this chart indicate the total number of people for each religious group:

The changing religious landscape is revealed by the variation with age. For people aged 65, the population is 25% Catholic, 24% secular, 22% Anglican, 16% other Christian, 7% Uniting Church, 2% Buddhist, 1% other religion, 1% Muslim, and 1% Hindu.

For people aged 25, it’s 47% secular, 21% Catholic, 11% other Christian, 8% Anglican, 4% Muslim, 3% Hindu, 3% Buddhist, 2% Uniting Church, and 2% other religion. The chart below shows these relative percentages, for each age cohort.

Immigration and children are keeping the Catholic Church stable in size, but the Uniting Church is in collapse, and the Anglican Church is not doing much better (other data suggests that it’s in collapse outside of Sydney). The “big three” non-Christian religions (Islam, Hinduism, and Buddhism) are more than 10% of the age-25 demographic. The chart also shows the impact of student-driven Indian immigration to Australia over the past decade or so – there is a visible peak for Hinduism around age 33.

There seems to be something odd about the religion given for young children up to age 13 or so – some parents (especially Catholics) seem to be listing young children as “no religion.” This might reflect delayed baptism. However, it also seems that many children lose their childhood religion in late teens and early adulthood.

Mean ages for adults within the different groups are Hindu: 37.1, Muslim: 37.7, secular: 42, other religion: 42.6, Buddhist: 43.5, Catholic: 48.6, other Christian: 50.4, Anglican: 54.8, and Uniting Church: 55.8. The last two groups in particular are skewed towards older people.


Solar car team composition

The chart above shows 2017 team composition for the Eindhoven and Bochum solar car teams (divided by study major, not team responsibility). Not surprisingly, electrical and mechanical engineering students are the core of both teams (about half in each case) Yet there is also considerable diversity, because the business side of a solar car team requires other skills too. The Bochum team also includes a media unit, which explains the large “other” category (one of the team photographers is a biology student, for example).

The chart was constructed by parsing web pages, which may have introduced errors (also, I guessed a bit with the German words). But the main point stands – solar car teams require a diverse set of skills.


The Bochum car (photo: Anthony Dekker)