DIGITAL IMAGE

Presentation By:

Saurabh Mishra

A digital image is a numeric (binary) representation of

a two dimensional image.

Digital images are of two types

• Raster Image

• Vector Image

Digital image usually refer to raster or bitmapped

images.

DIGITAL IMAGE

RASTER IMAGE

A Raster graphics image is a dot matrix data structure

representing a rectangular grid of pixels or points of

colour.

The smiley face in the bottom left corner is a

bitmap image. When enlarged, individual pixels

appear as squares. Zooming in further, they can

be analyzed, with their colors constructed by

adding the values for red, green and blue.

PIXELS

In raster image pixel is the smallest addressable

element which have its own characteristic.

In a digital image each pixel has its own color value

generally in rgb format.

COLOUR DEPTH

Colour depth (bit depth) is the number of bits used to indicate colour of a single pixel in a digital image.

COLOUR DEPTH NUMBER OF

COLOURS

1 bit 2 monochrome

2 bit 4 grayscale

4 bit 16

8 bit 256 VGA

24 bit 16777216 or 16M True Color

32 bit 4294967296 Deep Color

Color Depth:1 bit

Size:7.54 KB

Color Depth:4 bit Size:

30.2 KB

Color Depth:2 bit

Size:15.1 KB

Color Depth:24 bit

Size:181 KB

Color Depth:8 bit

Size:60.45 KB

RASTER IMAGE SIZE

The bits representing the bitmap pixels may be packed or

unpacked (spaced out to byte or word boundaries),

depending on the format or device requirements.

Depending on the color depth, a pixel in the picture will

occupy at least n/8 bytes, where n is the bit depth.

Size of image (in Bytes)=width*height*n/8

VECTOR IMAGE

Vector graphics is the use of geometrical primitives such as

points, lines, curves, and shapes or polygon(s), which are all

based on mathematical expressions, to represent images in

computer graphics

TYPICAL PRIMITIVE OBJECTS

Any particular vector file format supports only some kinds of

primitive objects. Nearly all vector file formats support simple and

fast-rendering primitive objects:

• Lines, polylines and polygons

• Bézier curves and bezigons

• Circles and ellipses

• Text

PRINTING

Vector art is ideal for printing. Since the art is made from a series

of mathematical curves, it will print very crisply even when

resized. For instance, one can print a vector logo on a small

sheet of copy paper, and then enlarge the same vector logo to

billboard size and keep the same crisp quality.

Standards

The World Wide Web Consortium (W3C) standard for vector

graphics is Scalable Vector Graphics (SVG). The standard is

complex and has been relatively slow to be established at least

in part owing to commercial interests. Many web browsers now

have some support for rendering SVG data.

Vector images could be magnified to any amount, it never

breaks into small pixels.

References

• Wikipedia• Google Images

Thank You!