User manual

Appendix - Still Images and Computer-based Graphics
78 Harmony 2ES and 4ES
Still Images and Computer-based Graphics
The information contained in this section outlines useful
techniques for creating still images and computer based
graphics for use in video.
Whether you are creating graphics that will be converted to
digital video or simply creating images that will be used as
graphic overlays, follow the guidelines below to make your
content more visually appealing and your desired message
more effective.
Screen Resolution and Pixels vs. DPI
Graphics that will be converted into MPEG2 should have a
resolution of 720x480 pixels.
Most graphics creation programs can be setup to use pixels as a
unit of measure instead of DPI. DPI (dots per inch) is used for
printing purposes and is not relevant to video. There is a
relationship-- the number of pixels will be equal to the DPI
value set in the software times the size of the canvas or printed
output size.
For example, suppose an image from a digital camera has a
resolution of 1000x500 pixels. If the printing software chooses
100 DPI, then the printed image will be 10 inches by 5 inches. If
250 DPI is chosen, then the image will be 4 inches by 2 inches.
When producing MPEG2 digital video, the “canvas size” is
720x480 pixels, and so to create a bitmap that will be part of a
composite image, the number of pixels should be chosen to be
smaller than 720x480. This means that a 72 DPI graphic that is
rendered out to 10 inches horizontally will fill the entire width
of one video line.
These guidelines serve only as recommendations and by no means repre-
sent technical data pertinent to any specific encoding device or process. It is
recommended prior to beginning any encoding project, sample files are
played back on the systems to be used to ensure proper display quality.