Cisco 8821 Administration Manual page 74

Custom Background Images
Tip Many graphics programs provide a feature that resizes a graphic. An easy way to create a thumbnail image
is to first create and save the full-size image, then use the sizing feature in the graphics program to create
a version of that image that is 25% of the original size. Save the thumbnail version by using a different
name.
The PNG files for background images must meet the following requirements for proper display on the phone:
• Full size image - 800 pixels (width) X 480 pixels (height).
• Thumbnail image - 139 pixels (width) X 109 pixels (height).
Tip If you are using a graphics program that supports a posterize feature for grayscale, set the number of tonal
levels per channel to 16, and the image posterizes to 16 shades of grayscale.
Cisco Wireless IP Phone 8821 and 8821-EX Administration Guide for Cisco Unified Communications Manager
64
Cisco Unified Communications Manager Phone Configuration