Alternative code for "Crystal in real life" post

main.cr

# Adapted from http://pfertyk.me/2016/11/crystal-in-real-life/

require "stumpy_png"

canvas = StumpyPNG.read("image.png")

canvas.width.times do |x|
  canvas.height.times do |y|
    color = canvas[x, y]
    
    # Original code
    grayscale = 0_u32
    grayscale = (grayscale + color.r + color.g + color.b) / 3

    # More idiomatic, without =0_32 initial assignment
    grayscale = (color.r.to_u32 + color.g.to_u32 + color.b.to_u32) / 3

    # Even more idiomatic, though slightly slower due to array allocation
    grayscale = [color.r, color.g, color.b].map(&.to_u32).sum / 3
    
    canvas[x, y] = StumpyPNG::RGBA.from_gray_n(grayscale, 16)
  end
end

StumpyPNG.write(canvas, "output.png")