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Resolution Independence

What is it?

Resolution Independence sounds like a complex term but its introduction could make computers significantly more accessible to many people with a variety of disabilities.

Resolution Independence is the concept that elements on a computer screen can be drawn at sizes independent from the pixel grid (see below).

It allows text and graphical elements to be resized without affecting the layout or clarity of the items. This means that elements can be made larger and therefore accessible to people with visual impairment. Large items, such as buttons, icons and menus, are also easier for people with physical difficulties to target using their trackball, joystick or other pointing device. Many people with learning difficulties also find less cluttered displays with larger elements easier to understand.

Here comes the science

A grid with a smiley face

Pixels

Computers display content using pixels. Any text, icon or other image placed on the screen is made up of pixels. Most Windows Desktop Icons, like the Firefox icon pictured, measure 32 pixels in both height and width. This applies to both CRT and TFT/LCD screens.

1024x768 Screenshot

72 DPI

1280x1024 Screenshot

115 DPI

1856x1392 Screenshot

167 DPI

Resolutions

The number of pixels a screen is made up from is traditionally referred to as its 'resolution'. This refers to the number of horizontal pixels and the number of vertical pixels and is usually written in the format Horiz. x Vert. For example 1024 x 768.

Megapixels

Some manufacturers now refer to this as 'megapixels' (millions of pixels) as this term is familiar to people who use digital cameras. A screen measuring 1280 pixels across by 1024 pixels down could be described as a 1.3 megapixel screen.

DPI

Microsoft have started describing screens by their DPI - Dots Per Inch (sometimes referred to as PPI - Pixels Per Inch). This is because DPI ties together screen size and pixel density and translates it into an actual, usable, physical & understandable form: inches.

For many years most screens had around 72 dots-per-inch and software was designed for this purpose. For example an icon, at 32 pixels square, was designed to be just under half an inch in size. This also explains the seemingly arbitrary values behind Microsoft Word's fonts sizes: 12pt fonts should measure 1/6th inch, 24pt is 1/3rd inch, 36pt is 1/2 inch and 72pt is an inch high.

Higher DPIs

The resolution of flat-panel displays has been gradually increasing. 150 dpi displays are commonplace, 200 dpi displays are readily available, and resolutions are likely to continue increasing. As a consequence of this everything on these computer screen is becoming significantly smaller than originally designed.

Any attempt at making these objects bigger can be complex and causes pixelation and/or layout problems.

Change the resolution and pixels can blur

Can't I change the resolution?

Just to confuse things slightly all screens do allow you to change their resolution without you even having to restart your computer.

This has the great benefit of making everything larger but unfortunately it fails to work properly on newer screens. Every flat-panel screen has a 'native resolution' and although you can usually force it to use a different resolution this usually results in poor picture quality and illegible text.

Availability of Resolution Independence

In order for a computer program to be scalable it needs two things:

  1. To have had the feature included by the programmer/s.
  2. To be supported by the Operating System (Windows, Linux, or Apple OS).

As far as I am aware there are currently no programs that meet this criteria. But all is set to change with the recent release of Windows Vista, and the upcoming Apple OS X 'Leopard'.

Windows Vista

Microsoft Windows Vista

Windows Vista uses a new Windows Presentation Foundation (WPF) graphics engine which allows scaling of any item - including entire windows - without blurring or pixelation. But this only applies to programs that have been designed to support scalability.

The Windows Vista Interface itself (the start menu, icons, system messages and so on) was originally intended to be fully resolution independent. They didn't manage this but it does have an adjustable DPI setting that is vastly improved over XP's. Further information on this shortly.

Windows XP

Microsoft Windows XP

The WPF graphics engine is available for Windows XP SP2 users as part of a free download External Link. The .NET Framework 3.0 allows modern programs designed for Vista to be compatible with XP, and this includes programs written to be resolution-independent.

The Windows XP User Interface will remain dependent on the pixel grid. Any enlargements have to be made through the Windows Display & Accessibility Options.

OS X 10.5 Leopard

Apple OS X 10.5 Leopard

Apple has confirmed that the forthcoming release of Apple OS X 10.5 will be fully resolution independent. Further information will appear here soon after the software is released (should be Spring 2007).

 

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