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Appendix A Introduction to Color
NI PCI-1405 User Manual A-2 ni.com
The perception of a color depends on many factors, such as the following:
• Hue, which is the perceived dominant color. Hue depends directly on
the wavelength of a color.
• Saturation, which is dependent on the amount of white light present in
a color. Pastels typically have a low saturation while very rich colors
have a high saturation. For example, pink typically has a red hue but
has a low saturation.
• Luminance, which is the brightness information in the video picture.
The luminance signal amplitude varies in proportion to the brightness
of the video signal and corresponds exactly to the monochrome
picture.
• Intensity, which is the brightness of a color and is usually expressed as
light or dark. For example, orange and brown may have the same hue
and saturation; however, orange has a greater intensity than brown.
Image Representations
Color images can be represented in several different formats. These formats
can contain all color information from the image or they can consist of only
one aspect of the color information, such as hue or luminance. The
following image representations can be produced using the NI 1405.
RGB
The most common image representation is 32-bit RGB format. In this
representation, the three 8-bit color planes—red, green, and blue—are
packed into an array of 32-bit integers. This representation is useful for
displaying the image on a monitor. The 32-bit integer is organized as
follows:
where the high-order byte is not used and the low-order byte is blue.
Color Planes
The red, green, or blue planes can be returned individually. Each plane is
extracted from the RGB image and represented as an array of 8-bit integers.
0 RED GREEN BLUE