GUIDED BY: PREPARED BY:

Prof. R.G.Patel Vijay Yadav (140403111014)

Prof.N.L.Rudani Ravi chaudhri(140403111016)

Sankalchand Patel collage of engineering

Subject : Fundamentals Images Subjectcode2171001

Prosessing

Colour Image Processing

Contents

Colour fundamentals.

Colour models.

Pseudo-colour image processing.

● Color :- three essential elements must be present: light, an

illuminated object, and an observer

● The use of colors in image processing is very important due

to :

o Color is powerful descriptor that simplifies object

identification

o Humans can recognize thousands of color compared to

only two dozen of gray levels.

● The beam of sun light is consisting of continuous spectrum of

colors ranging from violet at one end to red at the other end

(the experiment of the prism)

Color fundamentals

Color Modals

Is an abstract mathematical model describing the way colors can be represented as tuples of

numbers, typically as three or four values or color components.

When this model is associated with a precise description of how the components are to be

interpreted (viewing conditions, etc.), the resulting set of colors is called color space.

Type of color modal.

• RGB color model.

• NTSC color modal.

• YcbCr color modal.

• CMY and CMYK color modal.

• HIS color modal.

• RGB Model

RGB color modal

• In this model, the primary colors are red, green, and blue.

• It is an additive model, in which colors are produced by adding components, with

white having all colors present and black being the absence of any color.

• This is the model used for active displays such as television and computer screens.

• The RGB model is usually represented by a unit cube with one corner located at

the origin of a three-dimensional color coordinate system, the axes being labeled

R, G, B, and having a range of values [0, 1]. The origin (0, 0, 0) is considered black

and the diagonally opposite corner (1, 1, 1) is called white.

• he line joining black to white represents a gray scale and has equal components

of R, G, B

• Color printer and copier

• Deposit colored pigment

on paper

• Relationship with RGB

model:

8

C = CyanM = MagentaY = YellowK = Black

B

G

R

Y

M

C

1

1

1

CMY and CMYK color modal

• Cyan, magenta, and yellow are the secondary colors with respect to the primary colors of red, green, and blue. However, in this subtractive model, they are the primary colors and red, green, and blue, are the secondary.

• In this model, colors are formed by subtraction, where adding different pigments causes various colors not to be reflected and thus not to be seen. Here, white is the absence of colors, and black is the sum of all of them. This is generally the model used for printing

HSI Color Model

• RGB, CMY models are not good for human interpreting

Hue: Dominant color

Saturation: Relative purity (inversely proportional

to amount of white light added)

Intensity: Brightness

10

Color carryinginformation

Pseudo colour image processing.

• Assigning colors to gray values based on specified criterion

• Although the rods of the eye are sensitive to very low intensities, they have very

limited discrimination between gray levels. Generally, the eye cannot distinguish

more than about 50 gray levels in an image.

• Thus subtle detail can easily be lost in looking at gray scale images. To enhance

variations in gray level and make them more obvious, gray scale images are

frequently pseudo-colored, where each gray scale (generally at least 256 levels

for most displays) are mapped to a color level through a LUT.

• The eye is extremely sensitive to color and can distinguish thousands of color

values in a picture.

• Many different mapping schemes are used so that the variation in color, say from

blue to red, corresponds to human expectation of less to more.

Reference

www.google.com

www.wikipedia.com

Reface book

Rafael C. Gonzalez and Richard E. Woods

THANK YOU