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Appendix B Introduction to Color
IMAQ PCI/PXI-1411 User Manual B-2 www.ni.com
The perception of a color depends on many factors, such as:
• 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 which 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 just
one aspect of the color information, such as hue or luminance. The
following image representations can be produced using the PCI/PXI-1411.
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 your monitor. The 32-bit integer organized as:
where the high-order byte is not used and blue is the low-order byte.
Color Planes
Each color plane can be returned individually. The red, green, or blue plane
is extracted from the RGB image and represented as an array of 8-bit
integers.
0 RED GREEN BLUE