Understanding digital image- of which it consists
Adolf KnollNational Library of the Czech [email protected]
© 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>
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</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