boogdesign tutorials: File Type Guidelines

File Type Guidelines

General Advice

This document was originally written to stop my colleagues at work asking me questions a simple search on the internet would probably answer, not that it helped. It contains summary information and usage guidelines for most of the image and text file types you are likely to see during your working day. Each is useful in certain situations.

Images

Raster Formats

Raster formats store information about each pixel in the image. This makes them good for detailed images, such as photographs, the disadvantage is that raster images do not scale very well.

Bitmap (.bmp)

The most basic raster format, each pixel in the image has a colour associated with it.

Strengths: exact pixel for pixel representation, 24-bit colour possible

Weaknesses: large file size, no transparency

Good for: screenshots for printing

What can I use for viewing a BMP?

MS Paint (built in to Windows), Internet Explorer (built in to Windows), Windows Picture and Fax Viewer (built in to Windows XP), Microsoft Office Picture Manager (Built in to Office 2003), QuickTime Player, OpenOffice Draw, The GIMP, Inkscape, Xara Xtreme, Adobe Photoshop LE, Adobe Photoshop

Graphics Interchange Format (.gif)

Uses a lossless compression algorithm (the original image can always be regenerated) to reduce the amount of information required, significantly in the case where an image contains large areas of solid colour (eg. screenshots) but still stores a colour for each pixel.

Strengths: exact pixel for pixel representation, small file size (for the right type of image), allows transparency

Weaknesses: only 256 colours, file sizes similar to bitmaps for detailed images such as photographs

Good for: screenshots in general, logos for electronic use, images with large blocks of solid colour

What can I use for viewing a GIF?

MS Paint (built in to Windows), Internet Explorer (built in to Windows), Firefox, Opera, Windows Picture and Fax Viewer (built in to Windows XP), Microsoft Office Picture Manager (Built in to Office 2003), QuickTime Player, OpenOffice Draw, The GIMP, Inkscape, Xara Xtreme, Adobe Photoshop LE, Adobe Photoshop

JPEG (.jpg)

Uses a lossy compression algorithm (some of the original image data is lost) to reduce the amount of information required, especially for detailed images such as photographs. Different levels of compression are possible (0-100%) so file size can be tuned against image quality, colours are retained from the original image. Because the compression algorithm rebuilds the image using a fractal algorithm some of the original image detail is lost (it is replaced by 'similar' image parts), this is usually not detectable for photographs but produces very obvious colour variance in solid colour areas (such as on most screenshots).

Strengths: excellent compression for photo and photo-type images, tuneable image quality, full colour range

Weaknesses: very poor for areas of solid colour, no transparency

Good for: photographs and similarly detailed images

What can I use for viewing a JPEG?

MS Paint (built in to Windows), Internet Explorer (built in to Windows), Firefox, Opera, Windows Picture and Fax Viewer (built in to Windows XP), Microsoft Office Picture Manager (Built in to Office 2003), QuickTime Player, OpenOffice Draw, The GIMP, Inkscape, Xara Xtreme, Adobe Photoshop LE, Adobe Photoshop

Portable Network Graphics (.png)

A open standard developed following the exercising of the GIF patent by Compuserve, not really popular on Windows machines (because the OS doesn't handle them well), but offers several advantages over the GIF format, including the possibility of embedding (but not displaying) vector information. This is the native format of the Macromedia Fireworks graphics package.

Strengths: alpha transparency (works on any colour background), 24 bit or 8 bit colour, allows arbitrary meta-data to be included in image

Weaknesses: not well supported by all Windows applications, not as good compression as JPEG for photos

Good for: screenshots, logos for electronic use, images which need to be smoothly transparent against a variety of backgrounds

What can I use for viewing a PNG?

MS Paint (built in to Windows), Internet Explorer 7 (update for Windows), Firefox, Opera, Windows Picture and Fax Viewer (built in to Windows XP), Microsoft Office Picture Manager (Built in to Office 2003), QuickTime Player, OpenOffice Draw, The GIMP, Inkscape, Xara Xtreme, Adobe Photoshop LE, Adobe Photoshop

Tagged Image File Format (.tif, .tiff)

Designed by developers of printers, scanners and monitors for the publishing industry, TIFF offers a number of advantages for dealing with really large (high resolution) images and colour management.

Strengths: large images, colour management

Weaknesses: large file size, compatibility with some software poor

Good for: print ready artwork

What can I use for viewing a TIFF?

MS Paint (built in to Windows), Windows Picture and Fax Viewer (built in to Windows XP), Microsoft Office Picture Manager (Built in to Office 2003), QuickTime Player, OpenOffice Draw, The GIMP, Inkscape, AlternaTIFF, TIFF Reader, Xara Xtreme, Adobe Photoshop

Photoshop Drawing (.psd)

The native format of the hugely popular Adobe Photoshop package, originally developed to produce print ready raster artwork. Most printers will accept artwork in PSD format, but usually you will be producing artwork to be embedded into other file formats. Keep the original PSD file to maintain full editability.

Strengths: filters, fonts, layers etc. can be easily modified

Weaknesses: of limited use as an end format

Good for: master copies of artwork

What can I use for viewing a PSD?

QuickTime Player, OpenOffice Draw, The GIMP, Adobe Photoshop

eXperimental Computing Facility Format (.xcf)

The native format for the Gnu Image Manipulation Program (The GIMP), similar functionality to Photoshop but free. Again, use as a master document from which you produce the actual artwork.

Strengths: filters, fonts, layers etc. can be easily modified

Weaknesses: of limited use as an end format

Good for: master copies of artwork

What can I use for viewing a XCF?

The GIMP

Icon (.ico)

Icon format, most of the icons you see in Windows are in this format. Supports multiple resolution images embedded into a single file (because icons display at different resolutions depending on where you are looking at them - large on the Desktop than in the Start Menu for instance).

Strengths: transparency, multiple resolutions

Weaknesses: limited colours, limited in size, many viewers have limitations in their support for multiple resolutions

Good for: desktop icons

What can I use for viewing an ICO?

Windows Explorer (built in to Windows), MS Paint (built in to Windows), Internet Explorer (built in to Windows), Firefox, Opera, Windows Picture and Fax Viewer (built in to Windows XP), Microsoft Office Picture Manager (Built in to Office 2003), QuickTime Player, The GIMP, Inkscape, Xara Xtreme, IconForge

Raw (.raw)

The 'raw' image as output by most digital cameras when operating in 'high quality' or 'no compression' mode. Similar to a bitmap image. Generally you're better off converting to a JPEG for actual use.

Strengths: exact pixel for pixel representation, 24-bit colour possible

Weaknesses: large file size, no transparency, different versions of windows support different features

Good for: original artwork

What can I use for viewing a RAW?

MS Paint (built in to Windows), Internet Explorer (built in to Windows), Windows Picture and Fax Viewer (built in to Windows XP), Microsoft Office Picture Manager (Built in to Office 2003), QuickTime Player, The GIMP, Adobe Photoshop LE, Adobe Photoshop

Vector Formats

Vector formats describe images as a series of mathematical constructions (lines, arcs, polygons, curves). This makes them quite poor for detailed pictures such as photographs but immensely flexible otherwise. They can be scaled to any size/resolution and still have smooth edges which makes them especially good for printing. Most fonts on modern computers are represented in a vector format. Most vector formats can have raster images embedded in them (though these, of course, will not scale cleanly with the rest of the image), whereas the reverse isn't possible.

Windows Metafile (.wmf)

A fairly dated format, small file size but bad for curves

Good for: when you have no other options

Bad for: almost everything else

What can I use for viewing a WMF?

MS Paint (built in to Windows), Windows Picture and Fax Viewer (built in to Windows XP), OpenOffice Draw, The GIMP, Inkscape, Microsoft Office Picture Manager (Built in to Office 2003), Microsoft Word, Adobe Illustrator

Extended Metafile (.emf)

An update to WMF, similar in most respects.

Good for: when your options are limited to WMF or EMF

Bad for: almost everything else

What can I use for viewing a WMF?

MS Paint (built in to Windows), Windows Picture and Fax Viewer (built in to Windows XP), OpenOffice Draw, The GIMP, Inkscape, Microsoft Office Picture Manager (Built in to Office 2003), Microsoft Word, Adobe Illustrator

Encapsulated Postscript (.eps)

This format was originally developed for printing and typesetting, most quality printers accept Postscript directly as input. Most of the more advanced vector formats can therefore be translated back into Postscript fairly easily.

Strengths: a well known, well understood and common standard, suitable for supplying to printers and typesetters, contains colour management information

Weaknesses: Editability can be limited, file sizes can be large (especially if fonts need to be embedded)

Good for: Exchange between different platforms, print ready artwork

What can I use for viewing an EPS?

GSView, Adobe Reader, Adobe Acrobat, Adobe Illustrator

Adobe Illustrator (.ai)

This is the native format of Adobe Illustrator, a popular vector graphic drawing tool. It is an extension of the Postscript standard, most of the extensions relate to preserving editing information. Many printers will accept .ai drawings directly, and the file format is interchangeable between PC and Mac versions of Illustrator.

Strengths: Editability is retained

Weaknesses: Not as widely supported as .eps

Good for: Source documents used to generate print ready artwork

Portable Document Format (.pdf)

Another extension of the Postscript format, this time focussed on electronic documents. PDF files can be encrypted and have DRM signatures embedded in them to prevent tampering and also feature internal compression. Attached raster images can be compressed in either lossy or lossless mode and at a predefined resolution (DPI). Recent developments have leaned towards making PDF a better format for printing directly from.

Strengths: Searchable, can easily be produced suitable for web, screen or print, can be made very difficult to tamper with, built in compression

Weaknesses: Difficult to edit, file size can increase rapidly if many raster images are embedded

Use for: Documents you don't want people editing (eg. legal), logos, print ready documents

Shockwave Flash (.swf)

Developed for Macromedia's Flash and Shockwave products, this is basically a vector format but is designed for animation and embedding rich media for eg. presentations and/or training videos. The main advantage it has over other vector formats is that it comes with an embedded scripting language which makes it possible to build interactive animations.

Strengths: Works on a variety of platforms, scriptable, can embed movies and sound without requiring a separate player

Weaknesses: The flash player needs to be pre-installed (97% of Windows PCs have a version of the Flash player installed already)

Use for: interactive movies, computer based training, web based presentations

AutoCAD Interchange Format (.dwf)

DWF is basically PDF for drawings. It is Autodesk’s solution for sharing AutoCAD drawings with people who do not have AutoCAD and on the web. It is used when you want a user to be able to view and plot, but not edit, a large format drawing. You need a free viewer to view the files.

Strengths: small file size, reliable printing to large sizes. Good representation of CAD data

Weaknesses: not many people have the viewer, not good for non-CAD data, not as accurate as the original CAD file so not suitable as a basis for new drawings

Good for: read only viewing of AutoCAD drawings and publishing CAD data on the Web

Additional: DWF has a few predecessors in the form of Drawing eXchange Format (.dxf) and plot files (.plt)

Visio (.vsd)

Visio is a useful diagramming tool for producing flowcharts, block diagrams, user interface prototypes and UML etc; this is its native file format. This is the format you would save your work in while working on a diagram in Visio. It can be viewed using a viewer downloaded from Microsoft, but users are unlikely to have the viewer. This format is not suitable for general release; documents should be converted to images or PDFs for distribution.

Strengths: preserves the full functionality of your Visio drawing

Weaknesses: none really, it's just not ideal for distribution purposes because of limited support outside of Visio

Good for: master copies of Visio drawings and creating templates, convert the drawing to a more widely accepted format for distribution

Scalable Vector Graphics (.svg, .svgz)

This is a dialect of XML which has been pushed by Adobe as an alternative to Flash, it is an open standard so no one company controls it. Most modern drawing programs can export and import files in this format, files can be viewed using a free plugin for Internet Explorer or natively in upcoming releases of Mozilla and Firefox.

Strengths: open standard, files are human-editable using a text editor

Weaknesses: although many applications support most of the format they don't all support the same subset, so they all tend to render it differently

Good for: web graphics generated directly from spatial data

Text Documents

Editable

Text Format (.txt)

The basic document format, Word can be used to edit text documents but the default Windows editor is Notepad. Note that Windows has an unusual (compared to Mac and other OSes) line ending format, which can lead to garbage characters being displayed at the end of lines on other systems.

Strengths: The most space efficient way of storing a document, highly amenable to further compression using eg. WinZip, can be read by anyone, anywhere, on any device

Weaknesses: No formatting (no corporate style possible)

Good for: If you plan to import the same text into multiple sources (eg. Word, web pages, postscript artwork, desktop publishing software, databases) then write it first as text. Also useful if you want to strip unwanted style information from a Word document – save as text and import into a blank document

Rich Text Format (.rtf)

A lightweight Microsoft standard with embedded font and colour information, can also embed images if required. It is the native format of WordPad, and Word documents can also be saved as RTF (though Word embeds a large amount of extra information). By default Outlook composes messages in RTF format, though this causes problems for all non-Exchange based email systems, if you want to send formatted emails better to use HTML

Strengths: Widely accepted as a standard, easily editable

Weaknesses: Formatting control is limited

Good for: Documents that you want to have specific font formatting but be readable and editable by a wide range of (possibly non-Windows) users

Bad for: Large, complex documents (requiring headers/footers, sections, tables, contents pages)

Word (.doc)

The de-facto standard for document exchange in the Windows world, can also be read and/or imported (in most cases) by other word processors because of this.

Strengths: A wide variety of document creation and management tools, including auto numbering of sections, footnotes, figures, auto creation of tables of contents and indices, version management and others, it is possible to embed almost anything into a Word document (though not easy to get the embedded item back out again – don't paste directly into Word, create an image and import it, always retain your original for easy re-use)

Weaknesses: Not many people know or understand most of the better features, style control is poorly implemented (no clear distinction between word and paragraph styles) and default Word configuration compounds these problems, very easy to produce bloated documents

Use for: general purpose communications, frequently updated documents, collaboration

HTML (.htm, .html)

The standard document format of the World Wide Web. Can be edited directly as a text document, Word can also generate HTML documents but tends to produce extremely bloated code.

Strengths: Display formatted text on a huge variety of devices, easy to produced an interlinked set of documents

Weaknesses: Need to learn code conventions or get a special WYSIWYG editing tool

Use for: web pages, formatted emails

Adobe InDesign Document (.indd)

The native format of Adobe InDesign, a desktop publishing system. This is a full typesetting and document creation tool offering full control of colour spaces, type (kerning, leading etc.) and the embedding of other artwork. It can produce output in a number of formats, the most useful of which is PDF.

Strengths: precise control of page and text layout, direct embedding of EPS, AI and PSD images retaining colour information

Weaknesses: not much use as an end format, convert to PDF for distribution

Use for: professional quality publications, graphic intensive multiple page PDF documents, print ready documents

Read only

Portable Document Format (.pdf)

Already discussed in the image section, PDF is useful if you don't want the recipient of a document to be able to edit it easily.

boogdesign tutorials : FileTypeGuidelines

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