Sorry. They were relevant questions. Is this image good enough for you? I made it with couple lines of Perl from one of those screws. It's indexed, so you can take a look at palette. Which, yes, was extracted from gold ingots from your picture. If you intend to color grayscale images, then OK, it will work. If you meant something more complex (to me - something too much complex), though then I don't understand why you limit yourself to 256 shades, then OK, it won't work.

Edit: 

pdl> ( $im, $palette ) = rimage( 'test2.png', { palette => 1 })
pdl> $x = sequence( 255 )-> dummy( 0, 100 )-> byte
pdl> $x-> wimage( 'grad.png', { palette => $palette })

[download]

Actually this then "grad.png" is exact solution to the problem as stated in OP:

goal is to reduce those 62770 pixel values to a coherent, progressive, aesthetically pleasing 'gold scale' (after 'greyscale) of 256 values running from black to white, but encompassing as much of the range (nebulous term) of the full dataset as possible.

In reply to Re^3: A data selection problem(in3D). by vr
in thread A data selection problem(in3D). by BrowserUk

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