Initial commit: ZPL-native PDF printing, drop CUPS dependency

app.rb

@@ -0,0 +1,138 @@
+# /usr/bin/env ruby
+require 'sinatra'
+require "sinatra/reloader"
+require 'tmpdir'
+
+set :protection, :except => :frame_options
+set :environment, :production
+set :bind, "::"
+set :port, 4567
+
+if !File.exist?('config.json') || !File.readable?('config.json')
+  raise RuntimeException, 'Could not read config.json'
+end
+
+PRINTER_DEVICE = '/dev/usb/lp0'
+PRINTER_DPI = 203 # DatamaxONeil E4204B Mark III native head resolution
+PRINTER_DARKNESS = 8 # lower than factory default to stop thermal dot-gain from fusing barcode bars
+TEST_LABEL_PDF = File.join(File.dirname(__FILE__), 'test-label.pdf')
+
+configure do
+  enable :static
+  set :session_secret, File.read(File.join(File.dirname(__FILE__), '.session_secret')).strip
+  enable :sessions
+
+  set :views, File.join(File.dirname(__FILE__), 'views')
+  set :public_folder, File.join(File.dirname(__FILE__), 'public')
+  set :files, File.join(settings.public_folder, 'files')
+  set :unallowed_paths, ['.', '..']
+end
+
+configure :production do
+  enable :reloader
+end
+
+helpers do
+  def flash(message = '', level)
+    case level
+    when "success"
+      session[:alert_success] = message
+    when "danger"
+      session[:alert_danger]  = message
+    when "warning"
+      session[:alert_warning] = message
+    end
+  end
+
+  # Renders a PDF to ZPL ^GFA graphic labels at the printer's native DPI,
+  # bypassing CUPS/Gutenprint's raster pipeline which blurs text and 1px-shifts
+  # output compared to native ZPL rendering.
+  def pdf_to_zpl(pdf_path, dpi: PRINTER_DPI)
+    Dir.mktmpdir do |dir|
+      pattern = File.join(dir, 'page-%03d.pbm')
+      ok = system('gs', '-q', '-dNOPAUSE', '-dBATCH', '-dSAFER',
+                  '-sDEVICE=pbmraw', "-r#{dpi}",
+                  '-dTextAlphaBits=4', '-dGraphicsAlphaBits=4',
+                  "-sOutputFile=#{pattern}", pdf_path)
+      raise 'ghostscript rendering failed' unless ok
+
+      Dir.glob(File.join(dir, 'page-*.pbm')).sort.map { |f| pbm_to_zpl_label(f) }.join
+    end
+  end
+
+  def pbm_to_zpl_label(pbm_path)
+    bytes = File.binread(pbm_path)
+    header = /\AP4\s+(?:#[^\n]*\n\s*)*(\d+)\s+(\d+)\s/.match(bytes)
+    raise "unreadable PBM header in #{pbm_path}" unless header
+
+    width, height = header[1].to_i, header[2].to_i
+    bytes_per_row = (width + 7) / 8
+    total_bytes = bytes_per_row * height
+    body = bytes.byteslice(header.end(0), total_bytes)
+    hexdata = body.unpack1('H*').upcase
+
+    "^XA\n^MD#{PRINTER_DARKNESS}\n^PW#{width}\n^LL#{height}\n^FO0,0^GFA,#{total_bytes},#{total_bytes},#{bytes_per_row},#{hexdata}\n^XZ\n"
+  end
+end
+
+before do
+  @alert_success = session.delete(:alert_success)
+  @alert_danger  = session.delete(:alert_danger)
+  @alert_warning = session.delete(:alert_warning)
+end
+
+
+get '/' do
+  erb :index
+end
+
+get '/upload' do
+  erb :upload
+end
+
+post '/upload' do
+    if params[:file]
+
+      tempfile = params[:file][:tempfile]
+      filename = params[:file][:filename]
+      filetype = File.extname filename
+      filepath = File.join(settings.files, filename)
+
+      File.open(filepath, 'wb') do |f|
+        f.write tempfile.read
+      end
+
+      case filetype
+      when ".pdf"
+        begin
+          zpl = pdf_to_zpl(filepath)
+          File.open(PRINTER_DEVICE, 'wb') { |f| f.write(zpl) }
+          flash "PDF: Upload successful (#{filename})", "success"
+        rescue => e
+          flash "PDF: Failed to print (#{e.message})", "danger"
+        end
+      when ".zpl"
+        File.open(PRINTER_DEVICE, 'wb') { |f| f.write(File.binread(filepath)) }
+        flash "ZPL: Upload successful (#{filename})", "success"
+      else
+        flash "#{filetype} is not supported. Only .pdf and .zpl!", "false"
+      end
+
+      File.delete(filepath) if File.exist?(filepath)
+    else
+      flash 'You have to choose a file', "warning"
+    end
+
+    redirect '/upload'
+end
+
+post '/test-print' do
+  begin
+    zpl = pdf_to_zpl(TEST_LABEL_PDF)
+    File.open(PRINTER_DEVICE, 'wb') { |f| f.write(zpl) }
+    flash 'Test label sent to printer', 'success'
+  rescue => e
+    flash "Test print failed (#{e.message})", 'danger'
+  end
+  redirect '/upload'
+end