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I would like to generate a custom picture that, when projected on a brick wall, would produce compensate for the bricks and mortar; to produce a visually uniform background (say white) to project yet another picture/video on.
I could imagine how to do it from a CIE chart and have played with "color exchange" in gimp; which is quite nice; and does demonstrate some problems with the idea, but they don't seem insurmountable with work.
I don't have clue about how to fabricate a picture, that when projected on the same wall, would produce a similar effect. Lacking a lot of money I would try it with two projectors overlapping; perhaps later getting a video system that would merge the two images, object and whitewash, in one computer to one visual. I apologize if this is a "newbie" question, but I am a "newbie" to graphics tools.

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Its not possible. For obvious reasons its possible to do a lot of stuff on a digital platform. But this does not extend to the projector platform since it does not work the same way.

First having two projectors does not really help instead they compete for each other. See each projector reacts to the wall independently of each other. Secondly now the projectors are blinded by each other. And third even if making a wall uniform with one projector would work it would only work in one position in space.

But i wont go into more details as this is a graphic design forum not a optical engineering forum. But by all means if you can make negative color (not just absence of it) then you could make this happen.

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  • Thanks for the answer! And if I generated a covering by doing it pixel by pixel using the CIE formulas? en.wikipedia.org/wiki/Chromaticity en.wikipedia.org/wiki/CIE_1931_color_space "it would only work in one position in space." That would be sufficient for my purposes. – rrogers Aug 11 '20 at 17:30
  • @rrogers unfortunately physics of light reflection is not covered by CIE or any tristimulus device. Anyway you can not do this because then you would lose black. If you could do this high powered projectors would do this but you can not. – joojaa Aug 11 '20 at 17:41
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    In other words: light from a projector can only make things lighter, not darker. – Wolff Aug 11 '20 at 19:10

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