Otherwise you may want to explain what you are actually trying to achieve.
Maybe give examples of what the source material is likely to be and what results you strive for.
Thank You for letting me grab your attention . I'll be very presice then:
I'd like to access pixel array that holds rgba values (actually - color space doesn't matter, it's just to illustrate my point). When I script in a browser in Canvas or via p5.js or processing, I get an array with values as follows: [ r, g, b, a, r, g, b, a ...], which I can loop through and change values without any problem with just "=" sign. I haven't seen a way to change just a pixel information in Photoshop without making any selection, just by changing variables in an array that holds all of the colors. Using selection or even adding eyedropper point and then moving it, creating an array is not an option... It just takes ages.
I've read multiple posts on forums and used my own "sorting" actions using color range and wind filter...
What I was hoping to get was effect similar to this:
but on selection.
I guess if it's not possible, I'll just add eyedropper point and move it inside bounds of selection, creating array with [r, g, b, a.. ] values and then use gradient with colors set in hierarchical order (ordered by lightness or hue) and I'll leave it render for a night . I was just thinking if there is any faster way.
Thank for your answers.