3025EMC Master Control Switching & Channel Branding
Revision 3.0.3 Page 143
If the image does not have an associated key file, the Overture™ software enables the user to select a
colour to use as a match colour (chroma key). All areas of the logo with this colour will have a
translucent/drop shadow effect. Of course it is up to the designer to ensure that the drop shadow
colour only exists in the areas where a translucent effect is desired. Otherwise, in some areas,
unintended holes in the fill will appear. If the user wants more than one degree of translucency in the
same logo, separate key and fill files must be used. For these reasons, it is recommended to always
use separate key and fill files.
7.1.2.4. File Formats
Modern graphics and images can come in a wide variety of file formats. The following criteria must be
addressed to determine what is best for this application. First of all, images are only as good as their
source. A highly compressed JPEG image or a 4 bpp (4 bits or 16 colours per pixel) will not have the
same quality as a full colour (24 bpp) image. The most accurate (to the final representation when being
displayed in video) format is a RGB image (as compared to CMYK or a lossy compressed format).
Overture™ can support a variety of image formats, including Tiff, TGA, and BMP. All files must be
saved with 24bit colour values. These were picked to encourage the user to use file formats that
provide the best results.
7.1.2.5. Sharp Edges and Skinny Lines
The final product, when combined with the video, has certain limitations that are not present when the
image was created with today's modern graphics software. Although sharp edges (or fast colour
changes) and small skinny lines can be created and displayed on a computer monitor, they may not be
as visually appealing after being output to video and displayed on a regular TV monitor. The artifacts
will be flickering on horizontal lines, banding on vertical edges or a combination on diagonal edges.
This is due to limitations that exist in video that are different from the computer world (this is beyond
the scope of this help file). For example, if the user draws a simple image using Windows Paint, the
result will have illegal edges as described. If the user uses higher-end drawing packages, they will
have an option to turn on a filter that automatically smoothes edges between the different areas of the
drawing (this may be called "Anti-Aliasing" or "Feathering"). To ensure that the image has properly
shaped edges, zoom in on a sharp edge. Ensure that there are at least 2 pixels (horizontally and
vertically) of transition between the two areas.
The above puts limits on the smallest size that an object can take. A small 1 pixel wide line cannot be
properly reproduced. Ensure that all lines are at least 2 pixels wide and their edges are shaped.
7.1.2.6. Logo Size
To determine the size that the logo should be created the total size of the picture and the size of the
logo that will be inserted will need to be calculated. For example, high definition video picture area is
about 1000 lines high and 2000 pixels wide. If the user wishes to insert a logo that is 1/32 the size of
the picture, then they should draw an image that is 1000/32=32 lines high and 2000/32=63 pixels wide.
Before starting, the user must configure the drawing package to create a drawing area of this size.
Warning: Creating images that are larger or smaller and then re-scaling them will
produce an image of poorer quality, than if the user was to create the image at the
proper 1:1 scaled size. The mathematical process of squeezing/expanding may
create unacceptable results, particularly on edges.
To Next Page
Loading...
