Store icon in BGRA format so runtime conversion is not necessary.

scripts/icon.rb

@@ -0,0 +1,20 @@
+#!/usr/bin/env ruby
+
+require "fileutils"
+
+ICON = "share/jes/icons/jes-32x32.png"
+OUTFILE = "src/jes/gui/icon.d"
+
+system(*%W[convert #{ICON} bgra:icon.bgra])
+icon_bgra = File.binread("icon.bgra")
+FileUtils.rm_f("icon.bgra")
+
+File.open(OUTFILE, "wb") do |fh|
+  fh.puts "module jes.gui.icon;"
+  fh.puts
+  fh.puts "const ubyte[] icon_32x32_bgra = ["
+  icon_bgra.bytes.each_slice(8) do |bytes|
+    fh.puts "    #{bytes.map {|b| sprintf("0x%02xu,", b)}.join(" ")}"
+  end
+  fh.puts "];"
+end