Appendix A StillColor
NI-IMAQ User Manual A-2
©
National Instruments Corporation
StillColor
StillColor is a technique you can use to acquire color images from
composite color video or RGB cameras using the PCI/PXI-1408
monochrome device. Use StillColor Composite mode to acquire color
images from a composite color video camera. Use StillColor RGB mode
to acquire color images from an RGB camera. StillColor composite
acquisition results in an image of much higher quality than the traditional
color decoding that can be obtained with a color image acquisition board.
To acquire a color image, the PCI/PXI-1408 acquires multiple frames from
the camera. Your computer CPU then processes the frames using the
StillColor algorithm and creates a single color image. Because StillColor
uses your computer CPU to process the image, the acquisition time for a
single image depends on your system performance. You can acquire
StillColor composite images at rates of up to 2 frames/s and StillColor
RGB images at rates of up to 10frames/s.
You can use StillColor in applications that require high-quality images of
still or very slowly moving objects. StillColor supports many different
image representations used in scientific or industrial applications, such as
RGB bitmap and single plane hue, saturation, luminance, and intensity.
StillColor also supports image averaging of up to 128 frames to increase the
dynamic range of the StillColor image. See the Introduction to Color
section later in this appendix for more information on image
representations.

StillColor Composite

In a composite color video signal, the color information (chroma) is
modulated in phase and amplitude around a sub-carrier frequency of
3.58 MHz (N TSC) or 4.43 MHz (PAL). The modulated signal is then
added t o the luminance information and the entire signal including
synchronization pulses is transmitted on a single line.

Traditional Color Decoding

On the receiver side or in your IMAQ board, the luminance and the chroma
signals must be separated before the color image can be decoded and
rebuilt. However, the modulated color information and some of the
high-frequency luminance information share the same frequency range
around the sub-carrier frequency. This sharing makes it impossible to
separate the two signals perfectly and, therefore, perfect reconstruction of
the original color image is not possible.
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