修改启动画面

ChromiumOS本质上还是Linux，因此对其启动画面Splash的修改还是Linux的那一套，以下分别对其进行描述：

ChromeBook

在ChromeBook上，Splash存在的路径为：

/usr/share/chromeos-assets/images_100_percent

如果只想修改本机的启动画面，最简单的方式就是修改该目录下的启动图片boot_splash_frame**.png即可。但如果想将新的Splash应用到系统编译中，则还需要更多的操作。

ChromiumOS系统编译

经过查找，可以知道ChromiumOS系统是将Splash放置在目录src/platform/chromiumos-assets/images_100_percent下，该目录下共有18个图片文件：

boot_splash_frame01.png
boot_splash_frame02.png
boot_splash_frame03.png
boot_splash_frame04.png
boot_splash_frame05.png
boot_splash_frame06.png
boot_splash_frame07.png
boot_splash_frame08.png
boot_splash_frame09.png
boot_splash_frame10.png
boot_splash_frame11.png
boot_splash_frame12.png
boot_splash_frame13.png
boot_splash_frame14.png
boot_splash_frame15.png
boot_splash_frame16.png
boot_splash_frame17.png
boot_splash_frame18.png

但是由于ChromiumOS系统编译时，默认是从网络下载源码进行编译，因此如果只是修改这些文件，其实并不会改动到最终编译后的系统，这里还需要先查找该目录是属于哪个ebuild包：

$ cros_workon --board=${BOARD} --all info | grep chromiumos-assets
chromeos-base/chromiumos-assets chromiumos/platform/chromiumos-assets src/platform/chromiumos-assets

可以看到，这里需要将chromeos-base/chromiumos-assets设置为使用本地代码编译才行。故在chroot环境中，还需要先执行如下代码再进行编译：

cros_workon --board=${BOARD} start chromeos-base/chromiumos-assets

则最终将这些Splash图片编译到目标目录chroot/build/quawks/usr/share/chromeos-assets/images_100_percent中，再打包到最后的ChromiumOS系统内。

Splash的使用

Splash图片在文件src/platform2/init/upstart/boot-splash.conf中被使用，该文件对应的git仓库为https://chromium.googlesource.com/chromiumos/platform2，该文件具体内容为：

# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

description    "Displays an animation while the system is booting"
author         "chromium-os-dev@chromium.org"

# boot-splash depends on udev-trigger-early because frecon does need
# graphics device to be ready to display splash screen and tty (ptmx)
# device to create terminals, it also uses input devices (though they
# can also be hotplugged).

start on stopped udev-trigger-early

script
  . /usr/share/cros/factory_utils.sh

  if ! is_factory_installer_mode; then
    # Set the backlight to 40% of its maximum level.
    BACKLIGHT_DIR=/sys/class/backlight
    if [ -d $BACKLIGHT_DIR ] &&
       [ -n "$(find $BACKLIGHT_DIR -maxdepth 0 ! -empty)" ]; then
      backlight_tool --set_brightness_percent=40.0 || true
    fi

    ASSETS=/usr/share/chromeos-assets
    ASSETS_200=$ASSETS/images_200_percent
    ASSETS_100=$ASSETS/images_100_percent

    # Use differently-sized images depending on the framebuffer width.
    if [ -e "$ASSETS_200/boot_splash_frame01.png" ]; then
      BOOT_IMAGES=""
      for image in "$ASSETS_200"/boot_splash_frame*.png; do
        BOOT_IMAGES="${BOOT_IMAGES} --image-hires ${image}"
      done
      for image in "$ASSETS_100"/boot_splash_frame*.png; do
        BOOT_IMAGES="${BOOT_IMAGES} --image ${image}"
      done
    else
      BOOT_IMAGES="$ASSETS_100"/boot_splash_frame*.png
    fi

    if is_factory_test_mode; then
      BOOT_IMAGES="${BOOT_IMAGES} /usr/local/factory/misc/boot_splash.png"
    fi

    DEV_END_USER=
    if is_developer_end_user; then
      DEV_END_USER=--dev-mode
    fi

    frecon --daemon --clear 0xfffefefe $DEV_END_USER --frame-interval 25 \
      $BOOT_IMAGES
  fi
end script