Understanding digital image- of which it consists

Adolf KnollNational Library of the Czech Republicadolf.knoll@nkp.cz

© Adolf Knoll, National Library of the Czech Republic

Image consists of elements

However, some images do not consist of these elements…

… as they consist ofvectors…

Line art as vector graphics or a bitmap?

5 KB as WMF

780 KB as BMP

5 KB as PNG/4bit

11 KB as JPEG (qf 70)

How does it function?

Analogue to Digital

Digital to Analogue

Stored digitally encoded information

Vector graphics

The image can be enhanced without structural disintegration

Used for CAD (computer aided design) and in DTP (desk top publishing)

Vector editors, e.g. Corel Draw! Scalable vector graphics (XML format

displayed graphically through software that can decode it)

<?xml version="1.0" standalone="no"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.0//EN" "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd"><svg xmlns="http://www.w3.org/2000/svg" width="100%" height="100%" ><desc>page1</desc>

<style type="text/css">.dfltt {font-family:Times New Roman;font-size:14px;font-weight:normal;text-decoration:normal;text-align:left;fill:black;}</style><defs><radialGradient id="Sshd1" fx="50%" fy="50%" x="95%" y="50%" gradientUnits="objectBoundingBox"><stop id="stop1" offset="0%" style="stop-color:rgb(248,188, 94);stop-opacity: 1.00;"/><stop id="stop2" offset="100%" style="stop-color:rgb(128,128,128);stop-opacity: 1.00;"/></radialGradient></defs><rect id="Bpage1" style="fill:#ffedc6;" width="100%" height="100%"/>;

<g id="Oobj48" style="fill:url(#Sshd1);fill-rule:evenodd;" transform="matrix(0.70,-0.54,0.65,0.85,407.00,276.00)"><rect id="Ggeo46" x="-230" y="-180" width=" 460" height=" 361" style="stroke:rgb(196,128,128);stroke-width:1" /></g><g id="Oobj1" style="fill:url(#Sshd1);fill-rule:evenodd;" transform="matrix(1.50,0.00,0.00,1.00,403.00,272.00)"><ellipse id="Ggeo1" cx="0" cy="0" rx="130.00" ry="99.00" style="stroke:rgb(128,128,128);stroke-width:1" /></g><g id="Oobj47" style="fill:none;fill-rule:evenodd;" transform="matrix(3.46,0.00,0.00,6.53,408.00,263.50)"><text id="Ggeo45" x=" -48px" y=" -7px" width=" 96" height=" 15" style="font-family:Arial;font-size: 12px;fill:rgb( 0, 64,128);" ><tspan x=" -48px" y=" 3px">Training Courses</tspan></text></g>

</svg>

Scalable Vector GraphicsSVG

Raster graphics – bitmaps

It consists of picture elements (pixels) created by matrix application of the scanning CCD element

Each pixel has its position The image can have max. the same number

of pixels as the scanning element If it has more… they are multiplied through

recalculation (at cameras e.g. difference between optical and digital zoom)

Digital Image

Raster graphics

(bitmaps) a matrix or eye

principle grid of dots BMP, TIFF, GIF, ...

Vector graphics

(line art) a plotting principle combination of various

basic graphic objects as lines, ellipses, …

Corel Draw! (CDR), AutoCAD (DXF), Encapsulated Postscript (EPS), WMF

One Pixel Dimension

the pixel has a dimension, but it has no size the number of pixels on a unit of length defines

resolution (usually taken as ‘dots per inch’ - dpi) on a flat-bed scanner the resolution of the scanner is

applied 1:1 to the scanned original in camera-like devices it can be applied to a smaller

or larger area - thus the resolution of the digital image will be higher or lower

this fact is a limit for our work

One Pixel Dimension

Pixel – spatial resolution

It is storedin a bitmap,where it hasa numberedaddress (x,y).

X

y

Horizontal resolution

Vertical resolution

Pixels: their size and dimension

Free rotation

Rotated 2 degreesright