2.
A color model is a specification of a 3D color co-
ordinate system and a visible subset in co-ordinate
system within all colors in particular color range.
Four types are,
RGB,
CMY,
YIQ,
CMYK.
COLOR MODEL
3.
YIQ model is used for NTSC(NATIONAL
TELEVISION SYSTEM COMMITTEE)broadcast.
This model was designed to separate chrominance( I
and Q ) from luminance Y.
This was the requirements in early televisions when
black and white set still were expected to pick up
and display what were originally color pictures
DEFINITION
6.
The Y –channels contains the luminous
information(sufficient for black and white TV) while
the I and Q channels carried the color information.
The color TV would take three channels Y,I and Q
and map the information back to R,G and B levels for
display on a screen.
YIQ MODEL
7.
The more bandwidth can be assigned to Y –
component because the human visual system is more
sensitive to changes in luminance than to changes in
hue or saturation.
The YIQ is the recoding of RGB color model.
It is used in television broadcasting using one
composite signal.
ADVANTAGE
8.
The ability of separation gray scale information from
color data property enables to represent the same
signal for both color and (black and white) sets,
using luminance component .
Used in video system for determining color
components because of its human visual system
characteristic.
The component Y might represent noise in
processing, transferring, and storage at shallow level.
9.
INPHASE =RED-YELLOW
QUADRATURE =BLUE-YELLOW
It is based on the CIE and XYZ color model.
Broadcast NTSC limits I to 1.3 MHz and Q to
0.4 MHz . I and Q are frequency interleaved into the
4 MHz Y signal, which keeps the bandwidth of the
overall signal down to 4.2 MHz .
11.
The YIQ representation is sometimes
employed in color image processing
transformations.
For example, applying a histogram
equalization directly to the channels in an
RGB image would alter the color balance of
the Image.
Histogram equalization -method in image
processing for contrast adjustment.
IMAGE PROCESSING
13.
NTSC encoding of YIQ:
4 MHz = Y (eye most sensitive to
luminance)
1.5 MHz = I (small images need 1 color
dimension)
0.6 MHz = Q
ENCODING
14.
The primary goals of the system were to
provide a signal that could be directly
displayed by black and white TVs, while also
providing easy coding and decoding of RGB
signals.
GOAL OF YIQ
16.
The color range is restricted in the color TV images
because of the information compression required for
the displayed image.
Due to the limitation of the YIQ standard the image
displayed in computer cannot be recreate in TV
screen.
DISADVANTAGES
