[root@localhost Desktop]# rpm -qi docker
Name : docker
Version : 1.5
Release : 5.el6
Architecture: x86_64
Install Date: Sat 02 May 2015 12:12:36 PM CST
Group : User Interface/X
Size : 37603
License : GPL+
Signature : RSA/SHA256, Fri 02 Jul 2010 05:28:52 AM CST, Key ID 3b49df2a0608b895
Source RPM : docker-1.5-5.el6.src.rpm
Build Date : Fri 02 Jul 2010 02:32:06 AM CST
Build Host : x86-05.phx2.fedoraproject.org
Relocations : (not relocatable)
Packager : Fedora Project
Vendor : Fedora Project
URL : http://icculus.org/openbox/2/docker/
Summary : KDE and GNOME2 system tray replacement docking application
Description :
Docker is a docking application (WindowMaker dock app) which acts as a system
tray for KDE and GNOME2. It can be used to replace the panel in either
environment, allowing you to have a system tray without running the KDE/GNOME
panel or environment.
[root@localhost Desktop]# systemctl start docker.service
Failed to issue method call: Unit docker.service failed to load: No such file or directory.
比如取每个点的rgba值得平均值，根据这个策略得到每个像素点如何计算得出合并后的像素点的数据。得到一个合并的iamgeData，
然后通过putImage方法弄到合并后的canvas中去。