Extract and sort colour values from a heatmap of PIN usage

extract.rb

#!/usr/bin/env ruby
# frozen_string_literal: true

# extract.rb

# See https://archive.is/2Qtyr
# Extract the colour values from a 700x700 heatmap png
# representing a 100x100 grid of all possible 4 digit
# PIN numbers 'abcd' with 'ab' on the X axis and 'cd'
# on the Y axis.

DATA = {}

# get_hex
# Convert our srgb(r,g,b) data to hex
# Annoyingly, we are getting names back as well, as ImageMagick sees fit.
def get_hex(srgb)
  if srgb !~ /^srgb/
    case srgb
    when 'red'
      srgb = "srgb(255,0,0)\n"
    when 'gold'
      srgb = "srgb(255,215,0)\n"
    when 'OrangeRed'
      srgb = "srgb(255,69,0)\n"
    when 'black'
      srgb = "srgb(0,0,0)\n"
    when 'orange'
      srgb = "srgb(255,165,0)\n"
    when 'DarkOrange'
      srgb = "srgb(255,140,0)\n"
    when 'white'
      srgb = "srgb(255,255,255)\n"
    when 'yellow'
      srgb = "srgb(255,255,0)\n"
    else
      puts "Look up #{srgb} and add it in."
      exit
    end
  end
  str = srgb[5..-2]
  (r, g, b) = str.split(',')
  r = r.to_i.to_s(16).rjust(2, '0')
  g = g.to_i.to_s(16).rjust(2, '0')
  b = b.to_i.to_s(16).rjust(2, '0')
  "#{r}#{g}#{b}"
end

# get_colour
# Use ImageMagick to extract the pixel colour from our target image at the given co-ordinates
def get_colour(px, py)
  res = `convert pin-heatmap.png -format "%[pixel:u.p{#{px},#{py}]\n" info:`
  res.chop # lose newline at end
end

# get_pixel
# Convert x and y to the correct pixel in the image
# Image has x axis l->r, and y axis bottom->top
# So 0,0 (PIN 0000) should return something like 0, 700 but
# 99,99 (PIN 9999) should return something like 700,0
def get_pixel(x, y)
  rx = (x * 7) + 3
  ry = (700 - (y * 7)) - 3
  [rx, ry]
end

# get_pin
# Convert x and y to the relevant pin
def get_pin(x, y)
  result = ''
  result += '0' if x < 10
  result += x.to_s

  result += '0' if y < 10
  result += y.to_s
  result
end

(0..99).each do |ab|
  (0..99).each do |cd|
    pin = get_pin(ab, cd)
    pix = get_pixel(ab, cd)
    col = get_colour(pix[0], pix[1])
    hex = get_hex(col)
    DATA[pin] = hex
  end
end

# This should not work, but seems to
pp DATA.sort_by { |_k, v| v }.reverse