How to capture specific region on page by Seacat

Since version 5.1, Seacat began to support capture specific region on page.
It's more flexible, more convenient, and easy to use.
There are 4 ways that you may use to do this:
1.By absolute location
User send command to Seacat:
viewport-rect x1 y1 width1 height1 x2 y2 width2 height2 ...
where (x1,x2,width1,height1) is the first snapshot zone, (x2,y2,width2,height2) is the second snapshot zone, etc.
For example, the command "viewport-rect 100 100 400 300" let Seacat capture the region which top left coordinate
is (100,100), zone width is 400, zone height is 300.
2.By IDs
If User has already known the element ID, gbar for example, he can get this element's thumbnail by Seacat command:
viewport-id gbar
In viewport-id command, user can provides one or more element IDs. 
3.By class names
User can get element's thumbnail by its class name:
viewport-class class1 class2 ...
Send "viewport-class adArea resArea" to Seacat, user will get any element's thumbnail
if its class attribute value has "adArea" or "resArea". 
4.By xpath
Command syntax:
viewport-xpath XPATH
For example, send command "viewport-xpath //div[@id='entInfo' or @class='bookInfo']", you will get all DIV's thumbnail which id
is "entInfo" or it's class is "bookInfo".