undefined | Better HN

0 pointsthanatropism6y ago0 comments

It's the color scheme. I think in matplotlib it's called "hot". I do a lot of 2D kernel density plots that by having a black zero level and dozens of contour levels produce a smooth look with aesthetics similarities to this. I used to use that scheme because "heatmaps" but stopped because of the pulsing illusion.

I'm not sure if this image is real color or just lightness value and they used a color scheme for drama.

0 comments

Mizza6y ago

Grrr, why aren't scientists all using perceptually uniforms color schemes! This would still look awesome in `plasma`. Is there any where I can get the data and do it myself?

One of my favorite talks ever is on this subject: https://www.youtube.com/watch?v=xAoljeRJ3lU

Osmium6y ago

'Inferno' would be nice for this, also perceptually uniform, and has the benefit that space is still black.

kardos6y ago

Can you run it through the colormap in reverse to (approximately) recover the data?

yehar6y ago

Based on my analysis the published image is too processed to be able to invert the colormap to get to the brightness temperature data. I had better luck with Paper IV Fig. 15. See: https://physics.stackexchange.com/questions/472641/what-woul...

thanatropismOP6y ago

Technically yes -- colormaps are 1-dimensional non-self intersecting curves in RGBA space. You just grab them by the... I mean just straighten them.

I don't know if an explicit formula for the colormap is given, but you can always do "xs = np.linspace(0,1,100); ys = { cm.hot(x):x for x in xs}" and recover an approximate inverse. Then apply this function to each pixel of the image.

knolan6y ago

You can easily remap it between different colour maps if you assume that is is a standard hot map.

3170706y ago

It's the latter. This is an image in radio-frequency brightness of the object, so not visible frequencies of light. But yeah, it also looks like the 'hot' colormap to me.

j / k navigate · click thread line to collapse