Generate a linear radial gradient in Love2D

gistfile1.lua

local function scale(x, min1, max1, min2, max2)
  return min2 + ((x - min1) / (max1 - min1)) * (max2 - min2)
end

local function distance(x1, y1, x2, y2)
  return math.sqrt((x2 - x1) ^ 2 + (y2 - y1) ^ 2)
end

function radialGradient(radius)
  local data = love.image.newImageData(radius * 2, radius * 2)
  
  data:mapPixel(function(x, y)
    local dist = distance(radius, radius, x, y)
    return 0, 0, 0, (dist <= radius and scale(dist, 0, radius, 255, 0) or 0)
  end)
  
  return love.graphics.newImage(data)
end