Crestron Isys TPS-6 Operation Manual page 38

Isys™ 5.7" Tilt Touchpanel
34 • Isys™ 5.7" Tilt Touchpanel: TPS-6
Bit Depth and File Size
A balance of performance and quality can be achieved by using VT Pro-e to
configure the size of graphics in a project. Read this section to learn about bit depth
and how to maximize the quality and performance of a TPS-6 project.
Bit depth refers to the number of memory bits used to store color data for each pixel
in a raster image. A touchpanel 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 contain 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 and (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 near 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 translucence. 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 such as touchpanels, 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 mostly 8-bit or 16-bit graphics and holding 32-bit graphics
to a minimum (e.g. for a family photo, etc.), you can create a sophisticated project
that will fit in the memory space provided and have the touchpanel remain very
responsive.
Relationship of Bits to Colors
NUMBER OF BITS
1 bit
2 bits
4 bits
8 bits
16 bits
24 bits
32 bits
NUMBER OF COLORS
Black and White
4 Colors
16 Colors
256 Colors
65,536 Colors (Highcolor)
16.7 million Colors (Truecolor)
16.7 million Colors plus Transparency
Operations Guide – DOC. 6945A
Crestron TPS-6