Pictures on computers

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Pictures / images on computers Images are important



Why learn the basics of images? Pictures/graphics/images are often inserted in » word processing documents » presentations with slides » web pages  Therefore, it is interesting to know how » to acquire images » to change or improve images » to adapt images to the chosen output medium



Why learn the basics of images? • Scanning a document yields a picture, not a text. (OCR can then exploit the picture to yield a text in some cases.) • Pictures in a collection must be managed: »Storing »Making backups »Ordering / sorting images in a structure that can be browsed • This can be needed at a personal or institutional level, as a component of digital assets management.



Why learn the basics of images? Documents are more and more made available through the Internet.  Therefore it is important to make the file sizes small, while preserving an appropriate image/picture quality.



Pictures / images on computers Raster graphics versus vector graphics



?? Question ??

Explain the differences between raster graphics and vector graphics.



!! Task - Assignment !! •Create a small circle with a paint program for raster graphics and save this as a file.

•Create a small circle with a draw program for vector graphics and save this as a file. •Open each of both files again applying the same program that you used to create it and ENLARGE the circle.



!! Task - Assignment !!

•What is the difference between the resulting drawings (on screen as well as printed)?



Graphics formats: raster and vector graphics • Raster graphics used in programs for “painting”

• Vector-based graphics used in programs for “drawing”



Graphics formats: raster & vector graphics compared


Raster graphics Vector graphics

•Suited for “painting” and “retouching”



•Resolution adapted to output medium





•Size of files



?? Question ??

In which procedures are vector-based graphics converted to raster graphics?



?? Question ??

Why can raster graphics not be as easily converted to vector graphics, as vector graphics can be converted to raster graphics?



?? Question ??

What is easier: Converting raster graphics to vector graphics or the other way? Explain.



File formats for raster graphics only File name extension



Microsoft bitmap CompuServe / Unisys JPEG Z-Soft Paintbrush W3C Microsoft compressed bitmap Aldus PageMaker ...



File formats for vector graphics File name extension Name / Origin CDR CGM EPS SVG ...

Corel Draw! Graphics Metafile Encapsulated PostScript Scalable Vector Graphics ...



!! Read !!

Read Scalable Vector Graphics. [online] Available free of charge from: [cited 2005]



Graphics formats: the problem of exchange The differences in all the graphics file formats cause the requirement of filter / conversion programs, when a graphics file must be inserted in a document which is managed by an application program which works primarily wi