Computer Graphics and Multimedia

1. Color Models
Color Spaces

2. Introduction to Color Spaces
• Color spaces are the mathematical representation of a set of
colors.
• There are many color models.
• Some of them are RGB, CMYK, YIQ, HSV, and HLS, etc.
• These color spaces are directly related to saturation and
brightness.
• All of these color spaces can be derived using RGB
information using devices such as cameras and scanners.

3. RGB Color Space
• RGB stands for Red, Green, and Blue. This color space is widely used in computer
graphics. RGB are the main colors from which many colors can be made.
• RGB can be represented in the 3-dimensional form:

4. RGB Color Space
Properties:
• This is an additive colour model. The colours are added to the black.
• 3 main channels: Red, Green and Blue.
• Used in DIP, openCV and online logos.

5. RGB Color Space
• Color bar contains values for 100% amplitude, 100% saturated, and for video test
signal.

6. CMYK Color Model
• CMYK stands for Cyan, Magenta, Yellow and Black.
• CMYK color model is used in electrostatic and ink-jet plotters
which deposits the pigmentation on paper.
• In these model, specified color is subtracted from the white
light rather than adding blackness.
• It follows the Cartesian coordinate system and its subset is a
unit cube.

7. CMYK Color Model
• It is a subtractive colour model.
• 0 represents the primary colour and 1 represents the lightest
colour. In this model, point (1, 1, 1) represents black, and
(0,0,0) represents white.
• It is a subtractive model thus the value is subtracted from 1
to vary from least intense to a most intense colour value.

8. CMYK Color Model

9. HSV Color Model
• HSV stands for Hue, Saturation, and Value (brightness).
• It is a hexcone subset of the cylindrical coordinate system.
• The human eye can see 128 different hues, 130 different saturations
and number values between 16 (blue) and 23 (yellow).

10. HSV Color Model

11. HSV Color Model

12. HSV Color Model

13. YIQ Color Model
• YIQ is the most widely colour model used in Television broadcasting.
• Y stands for luminance part and IQ stands for chrominance part.
• In the black and white television, only the luminance part (Y) was
broadcast.
• The y value is similar to the grayscale part. The colour information is
represented by the IQ part.
• There exist a formula to convert RGB into YIQ and vice-versa.

14. YIQ Color Model (Conversion matrix)
YIQ model is used in the conversion of grayscale images to RGB colour images.