Crestron TPS-G-TPI Operation Manual page 42

G-Series Touchpanel Interface
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38 ¥ Isys G-Series Touchpanel Interface: TPS-G-TPI
Bit Depth and File Size
A bit depth refers to the number of memory bits used to store color data for each
pixel in a raster image. A TPS-G-TPI raster image consists of a rectangular grid of
picture elements (pixels). Each pixel uses the same amount of memory to store its
color data. The amount of memory is called the bit depth of the image.
Greater bit depths are required to represent finer gradations of color. Increasing bit
depth necessarily increases file size. A black and white drawing requires only one bit
per pixel to store all the available color information. Using a 32-bit per pixel bit
depth for a black and white image increases the file size 32 times, without adding
anything to the black and white image quality.
In an 8-bit per pixel system, the associated 8-bits of video memory for every screen
pixel, contains a value referring to a location in an 8-bit color table. In this way, any
one of the specific 256 color table locations is assigned to a pixel.
A 16-bit highcolor system is considered sufficient to provide life-like colors. It is
encoded using 5-bits to represent red, 5-bits to represent blue, but (since the human
eye is more sensitive to the color green) 6-bits to represent 64 levels of green. These
can therefore be combined to provide 65,536 mixed colors (32 x 32 x 64 = 65,536).
In a 24-bit graphics display, the video memory allocates 24 bits for each pixel on the
screen, enabling each pixel to take on any one of a possible 16.7 million colors. Each
24-bit value is composed of 8-bits for red, 8-bits for green, and 8-bits for blue. These
triplets of 8-bit values are also referred to as the red, green, and blue color planes. A
24-bit image is actually composed of three component images, which combine to
create the truecolor picture. The reason this is called truecolor is that this is around
the maximum number of colors the human eye is able to detect.
Truecolor images are sometimes represented by a 32-bit value. The extra 8-bits do
not enhance the precision of the color representation, but act as an alpha channel that
represents pixel translucency. The 32-bit truecolor has become popular on the
computer desktop to provide effects such as translucent windows, fading menus, and
shadows.
In graphics intensive applications, raising or lowering the color depth of the
displayed graphics can achieve a balance of performance and quality. Lower color
depths do not require as much frame buffer memory or display bandwidth, allowing
them to be generated and displayed more quickly. Increasing color depth results in
higher color quality at the expense of display speed and responsiveness. By using a
majority of 8-bit or 16-bit graphics, and holding the 32-bit graphics to a minimum
(ex. for a family photo, etc.), you can create a sophisticated project that will fit in the
memory space provided, and have the interface remain very responsive.
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Crestron Isys TPS-G-TPI
Operations Guide – DOC. 6445