Question

I created the current code quite a while back in which I provide the starting and ending colors and the number of steps. Returned is a table (an array) of the colors in between the starting and ending colours.

function getColorSteps(starting, ending, steps)
    steps = tonumber(steps) or 1

    local step = {
        (ending[1] - starting[1]) / steps,
        (ending[2] - starting[2]) / steps,
        (ending[3] - starting[3]) / steps
    }

    local palette = {
        [1] = { unpack(starting) },
        [steps] = { unpack(ending) }
    }

    for i=2, steps-1 do
        palette[i] = {
            starting[1] + (step[1] * i),
            starting[2] + (step[2] * i),
            starting[3] + (step[3] * i)
        }
    end

    print( "#palette = " .. #palette )
    print( "steps = " .. steps )
    for i = 1, #palette do
        print(
            i ..
            ". rgb(" .. 
            table.concat(palette[i], ", ")
            .. ")"
        )
    end

    return palette
end

I’d like to have this converted from steps to “progress”. See this example:

 s,e = {255,255,255},{0,0,0}

 getColorSteps(s,e,0)
 > 255, 255, 255, 255

 getColorSteps(s,e,0.5)
 > 127.5, 127.5, 127.5, 127.5

 getColorSteps(s,e,1)
 > 0, 0, 0, 0

I’m just not sure how to do it…

Answer 1

Maybe using linear interpolation?

function getColorSteps(s, e, interp)
    return { 
        (e[1]-s[1]) * interp + s[1],
        (e[2]-s[2]) * interp + s[2],
        (e[3]-s[3]) * interp + s[3],
        (e[4]-s[4]) * interp + s[4]
    }
end

That will however work only if in each of the corresponding color value i, e[i] > s[i]. So you would probably need to use math.max(e[0], s[0]) - math.min(e[0], s[0]) each time or something similar.

And, oh, I would rather use a and b instead of start/end; but it may be just my preference.