Computer file formats

1. Computer file formats Paul.Nieuwenhuysen@vub.ac.be • Vrije Universiteit Brussel • Informatie- en Bibliotheekwetenschap, Universitaire Instelling Antwerpen België Presented for the SAP project atKatholieke Universiteit Nijmegen, Nederland, 10 May 2001 These slides are available through the WWW from http://www.vub.ac.be/BIBLIO/nieuwenhuysen/presentations/

2. ***- Contents of this presentation • Introduction to file formats • File formats for text only • File formats for graphics/images • File formats for documents with text and images • File compression, archiving, conversion

3. ***- Introduction to file formats

4. ***- The relations between programs and file formats Programs to edit/create/develop/maintain a file in a particular format  File stored in a particular format  Programs to read/view files in a particular format + Programs to save=convert=export files from one format to another 

5. ***- The program functions editing, viewing, converting A program can incorporate only 1, 2, or all 3 of the functions • Editing / creating • Reading / viewing / interpreting • Converting / saving / exporting for particular file formats.

6. ***-Examples Examples of programs for editing, viewing, converting Examples: • Microsoft Word can create/edit + view/read + convert the file in the formats DOC, RTF, HTML. • Adobe Acrobat Reader can only view / read (but not create/edit or convert/save) files in PDF format.

7. ***- File formats for text only

8. Type Files containing unformatted ASCII text Files with text coded by the Hypertext Markup Language Normal file name extension .TXT .HTML or .HTM ***- File formats for text only: examples

9. **-- !? Question !? Task !? Problem !? Why can HTML files be considered as text only, even when many web pages made with HTML contain graphics/images/photos?

10. ***- File formats for graphics/images

11. **-- !? Question !? Task !? Problem !? Explain the differences between bitmap graphics with vector graphics.

12. **-- Graphics formats: bitmaps and vector graphics • Bitmap graphics used in programs for “painting” • Vector-based graphics used in programs for “drawing”

13. **-- !? Question !? Task !? Problem !? Draw a small circle with a paint program for bitmaps and save this. Draw a small circle with a draw program for vector graphics and save this. Select each drawing and enlarge it. What is the difference between the resulting drawings?

14. **-- Graphics formats: bitmaps compared with vector graphics • Property • Suited for “painting” and “retouching” • Resolution adapted to output medium • Size of files Bitmaps + - large Vector graphics - + small

15. ***-Examples Graphics formats for bitmaps only File name extension BMP GIF JPG PCX, PCC PNG RLE TIF ... Origin Microsoft CompuServe / Unisys JPEG Z-Soft PaintbrushW3C Aldus PageMaker ... Maximum number of colours maximum 256 colours more than 256 colours more than 256 colours

16. **-- !? Question !? Task !? Problem !? Which properties of graphics file formats for bitmap images are important?

17. Maximum number of colours in one image? Compression of file size? Compression without loss of quality? Animation possible? GIF 256 + + + Graphics formats for bitmap images: a comparison JPG 256*256*256 ++ - -

18. **-- !? Question !? Task !? Problem !? Estimate the typical size of a computer file that contains a bitmap image in colours, that has been obtained by using a typical scanner, and that can cover a complete typical display or projection screen directly at optimal resolution without enlargement, when no compression is applied.

19. **--Examples Graphics formats for vector graphics (+ bitmaps) File name extension CDR CGM EPSIMG PPT or PPS WPG ... Origin Corel Draw! Graphics Metafile Encapsulated PostScript GEM Microsoft PowerPoint WordPerfect Graphics ...

20. **-- 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 with another graphics file format.

21. **-- !? Question !? Task !? Problem !? Insert a picture, stored in a graphics file, in a document created by your program for word processing.

22. ***- File formats for documents with text and images

23. **-- !? Question !? Task !? Problem !? Which concrete file formats for storage of documents with text and images do you know?

24. ***- Documents with text and images: available file formats (Part 1) • Many! Too many? • Examples: • formats of the various programs for word processing and page design, in their various versions (DOC,…) • Rich Text Format (RTF) • PostScript (PS) • Adobe Portable Document Format (PDF); Catchword RealPage,...

25. ***- Documents with text and images: available file formats (Part 2) • bitmap-related format, primarily for graphics, but they can also show characters: BMP, GIF, JPG/JPEG, PCX, PNG, TIFF... • SGML, HTML, XML,... considered here together with the graphics files that they link to • …

26. **-- !? Question !? Task !? Problem !? Which properties of computer file formats for storage of documents with text and images do you consider as important?

27. **-- Documents with text and images: properties of file formats (Part 1) • Is the format platform independent? (for instance usable with software on Windows, Macintosh, Unix,…) • Is the format not proprietary? • Are files in this format small in comparison to the corresponding files in other formats? • Is compression applied? If yes, is this compression without loss of information?

28. **-- Documents with text and images: properties of file formats (Part 2) • Are viewers (programs) for users easily available? • Does the format allow text retrieval? Is the content of a file in this format searchable on a microcomputer? • Does the format allow text retrieval by common Internet indexes? Is the contents searchable through the WWW or through an intranet?

29. **-- Documents with text and images: properties of file formats (Part 3) • Can a file in this format be loaded in a program and be edited / modified / improved and saved? (or can it only be derived from a master file in another format?) • Can the text be reformatted to another size or font? • Can a selection be made from the displayed contents of a file in this format, by copy or cut, to be pasted in another document?

30. **-- Documents with text and images: properties of file formats (Part 4) • Does the format not suffer from the existence of various versions that may confuse the users and that require an appropriate, up-to-date program? • Is the format suitable when hard-copy documents are converted to computer-based documents? • Is a program to produce the format already available or not expensive?

31. **-- Documents with text and images: properties of file formats (Part 5) • Is the format ‘rich’, allowing to derive less rich formats from a file in this format? (for instance from Microsoft Word to RTF or HTML or PDF, from SGML to XML to HTML,...)

32. **-- !? Question !? Task !? Problem !? Discuss the properties (advantages and disadvantages) of each important file format TXT, DOC, RTF, PS, PDF, SGML, HTML, GIF, JPG, TIFFfor storage of documents with text and images? Summarize this in the form of a table: file formats versus their properties

33. **-- !? Question !? Task !? Problem !? What is the main conclusion of the overview of the properties of file formats for storage of text and images?

34. **-- File formats: the problem of exchange The differences in all the file formats cause the requirement of filter / conversion programs, when a file must be viewed or edited by an application program that is not exactly the same as the one used to create the file.

35. ***- File compression, archiving and conversion

36. :&&”FclPBT#$-D !3!!!%!&!!!!2’H#3) !%!f”9’!)!!+8QpcF ***- File compression, archiving and conversion • Compressionto make files smaller • Archiving to keep related files together • Conversion for transfer via computer networks

37. ***- !? Question !? Task !? Problem !? Which benefits are offered by compression of files?

38. ***- Data compression: benefits • Storage capacity required on magnetic or optical disks is smaller • In data communication: • transmission times are shorter • transfer of less bits ð less network congestion

39. **-- Data compression: redundancy Compression is (in many cases) based on the elimination of redundancy present in the source data: • Spatial redundancy: repeated occurrence of the same text or picture elements • Temporal redundancy: occurrence of the same picture elements in subsequent pictures

40. **-- Data compression: lossless versus lossy • Compression without loss of data / quality:“lossless” compression • Compression with loss of data / quality: “lossy” compression

41. **-- !? Question !? Task !? Problem !? Which concrete products, tools and methods for file compression do you know?

42. **--Examples Data compression: some CODECS • Compression without loss of data, and archiving: ARC, BOO, CAB, LHZ, ZIP, ZOO,... • Lossless compression of bitmap graphics: GIF, TIFF, ... in various versions • Lossy compression of graphics with many colours: JPEG, ... in various versions • Lossy compression of video with sound: AVI, MPEG, Quicktime, RM, ... in various versions

43. **-- !? Question !? Task !? Problem !? Find a file in .ZIP format and decompress it.

44. **-- !? Question !? Task !? Problem !? Why is it not useful to apply a compression procedure like ZIP for instance, to a video file in formats like AVI or MPG?

45. **-- !? Question !? Task !? Problem !? Which programs do you know and which program do you use to save images as JPEG files?

46. **-- !? Question !? Task !? Problem !? Select or create an appropriate photograph bitmap file. Save this file as a JPEG file under a different name. Repeat this at about 3 very different levels of compression and thus of image quality(always starting from the appropriate original photo file, because JPEG is a final storage format). Load all the resulting photo files in a program to edit such files; zoom in to 400% for instance;use tiling to display the photo files simultaneously on the screen; compare their quality. Determine also the file size of each photo file. Decide finally which compression level is appropriate or your aims.