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A comment on Unveiling the first-ever image of a black hole [video]. Parent comment

Re:Unveiling the first-ever image of a black hole [video] by thanatropism on Wednesday April 10, 2019 @09:35AM (#19624459)
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.

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Re:Unveiling the first-ever image of a black hole [video] by Mizza on Wednesday April 10, 2019 @12:17PM (#19626142)
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

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Re:Unveiling the first-ever image of a black hole [video] by Osmium on Wednesday April 10, 2019 @03:07PM (#19627776)
'Inferno' would be nice for this, also perceptually uniform, and has the benefit that space is still black.
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Re:Unveiling the first-ever image of a black hole [video] by kardos on Wednesday April 10, 2019 @03:00PM (#19627725)
Can you run it through the colormap in reverse to (approximately) recover the data?
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Re:Unveiling the first-ever image of a black hole [video] by yehar on Thursday April 18, 2019 @01:37AM (#19688964)
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...
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Re:Unveiling the first-ever image of a black hole [video] by thanatropism on Friday April 12, 2019 @02:44PM (#19647807)
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.

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Re:Unveiling the first-ever image of a black hole [video] by knolan on Thursday April 11, 2019 @03:00AM (#19631803)
You can easily remap it between different colour maps if you assume that is is a standard hot map.
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Re:Unveiling the first-ever image of a black hole [video] by 317070 on Wednesday April 10, 2019 @12:08PM (#19626058)
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.
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