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Computer file formats

Paul.Nieuwenhuysen@vub.ac.be

• Vrije Universiteit Brussel

• Informatie- en Bibliotheekwetenschap, Universitaire Instelling Antwerpen

België

Presented for the SAP project at Katholieke Universiteit Nijmegen, Nederland,

10 May 2001

These slides are available through the WWW fromhttp://www.vub.ac.be/BIBLIO/nieuwenhuysen/presentations/

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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

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Introduction to file formats

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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

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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.

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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.

***-Examples

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File formats for text only

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File formats for text only: examples

Type

• Files containing unformatted ASCII text

• Files with text coded by the Hypertext Markup Language

Normal file name extension

.TXT

.HTML or .HTM

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!? Question !? Task !? Problem !?

**--

Why can HTML files be considered as text only, even when many web pages made with HTML

contain graphics/images/photos?

Why can HTML files be considered as text only, even when many web pages made with HTML

contain graphics/images/photos?

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File formats for graphics/images

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!? Question !? Task !? Problem !?

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Explain the differences between bitmap graphics

with vector graphics.

Explain the differences between bitmap graphics

with vector graphics.

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Graphics formats: bitmaps and vector graphics

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• Bitmap graphics used in programs for “painting”

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

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!? Question !? Task !? Problem !?

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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?

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?

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Graphics formats: bitmaps compared with vector graphics

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Bitmaps

+

-

large

Vector graphics

-

+

small

Property

•Suited for “painting” and “retouching”

•Resolution adapted to output medium

•Size of files

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Graphics formats for bitmaps only

File name extension

BMPGIFJPGPCX, PCCPNGRLETIF...

Origin

MicrosoftCompuServe / UnisysJPEGZ-Soft PaintbrushW3C

Aldus PageMaker...

***-Examples

Maximum number of colours

maximum 256 coloursmore than 256 colours

more than 256 colours

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!? Question !? Task !? Problem !?

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Which properties of graphics file formats for bitmap images are important?

Which properties of graphics file formats for bitmap images are important?

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Graphics formats for bitmap images: a comparison

• Maximum number of colours in one image?

• Compression of file size?

• Compression without loss of quality?

• Animation possible?

GIF

256

+

+

+

JPG

256*256*256

++

-

-

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!? Question !? Task !? Problem !?

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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.

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.

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Graphics formats for vector graphics (+ bitmaps)

File name extension

CDRCGMEPSIMGPPT or PPSWPG...

Origin

Corel Draw!Graphics MetafileEncapsulated PostScriptGEMMicrosoft PowerPointWordPerfect Graphics...

**--Examples

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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.

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!? Question !? Task !? Problem !?

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Insert a picture, stored in a graphics file, in a document

created by your program for word processing.

Insert a picture, stored in a graphics file, in a document

created by your program for word processing.

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File formats for documents with text and images

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!? Question !? Task !? Problem !?

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Which concrete file formats for storage of documents

with text and images do you know?

Which concrete file formats for storage of documents

with text and images do you know?

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Documents with text and images: available file formats (Part 1)

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• 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,...

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Documents with text and images: available file formats (Part 2)

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»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

»…

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!? Question !? Task !? Problem !?

**--

Which properties of computer file formats for storage of documents

with text and images do you consider as important?

Which properties of computer file formats for storage of documents

with text and images do you consider as important?

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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?

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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?

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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?

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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?

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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,...)

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!? Question !? Task !? Problem !?

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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

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

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!? Question !? Task !? Problem !?

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What is the main conclusion of the overview of the properties

of file formats for storage of text and images?

What is the main conclusion of the overview of the properties

of file formats for storage of text and images?

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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.

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File compression, archiving and conversion

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File compression, archiving and conversion

• Compressionto make files smaller

• Archiving to keep related files together

• Conversion for transfer via computer networks

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:&&”FclPBT#$-D!3!!!%!&!!!!2’H#3)!%!f”9’!)!!+8QpcF

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!? Question !? Task !? Problem !?

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Which benefits are offered by compression of files?

Which benefits are offered by compression of files?

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Data compression: benefits

• Storage capacity required on magnetic or optical disks is smaller

• In data communication:

»transmission times are shorter

»transfer of less bits less network congestion

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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

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Data compression: lossless versus lossy

• Compression without loss of data / quality:“lossless” compression

• Compression with loss of data / quality: “lossy” compression

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!? Question !? Task !? Problem !?

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Which concrete products, tools and methods for file compression

do you know?

Which concrete products, tools and methods for file compression

do you know?

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Data compression: some CODECS

**--Examples

• 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

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!? Question !? Task !? Problem !?

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Find a file in .ZIP format and decompress it.

Find a file in .ZIP format and decompress it.

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!? Question !? Task !? Problem !?

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Why is it not useful to apply a compression procedure

like ZIP for instance, to a video file

in formats like AVI or MPG?

Why is it not useful to apply a compression procedure

like ZIP for instance, to a video file

in formats like AVI or MPG?

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!? Question !? Task !? Problem !?

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Which programs do you know and which program do you use to save images as JPEG files?

Which programs do you know and which program do you use to save images as JPEG files?

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!? Question !? Task !? Problem !?

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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.

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.