shard.yml

name: qr-api
version: 0.1.0

authors:
  - Jonathan B. <greenbigfrog@gmail.com>

targets:
  qr-api:
    main: src/qr-api.cr

crystal: 0.27.0

license: MIT

dependencies:
  stumpy_png:
    github: stumpycr/stumpy_png
  qrencode:
    github: woodruffw/qrencode.cr

test.cr

require "qrencode"
require "stumpy_png"
include StumpyPNG

qr = QRencode::QRcode.new("this is my input string")

size = 300
dead_percentage = 23

dead = (dead_percentage / 100.to_f * size).to_i
scale = (size - dead) / qr.width

qr_size = qr.width * scale + dead
if qr_size < size
  dead = size - qr_size + dead
  qr_size = qr.width * scale + dead
end

puts "Size: #{size} Scale: #{scale} Final width: #{qr_size}"

canvas = Canvas.new(qr_size, qr_size) do |x, y|
  x = (x - dead / 2) / scale
  y = (y - dead / 2) / scale
  if 0 <= x < qr.width && 0 <= y < qr.width
    if QRencode::Util.black?(qr.data[x + qr.width * y])
      RGBA::BLACK
    else
      RGBA::WHITE
    end
  else
    RGBA::WHITE
  end
end

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