The need for NewIcons arose from the poor overall quality of icons in AmigaOS versions prior to 3.0. While the AmigaOS GUI had been revolutionary when it was first launched in the early 1980s, other operating systems such as Mac OS and Microsoft Windows quickly caught on and started to become more professional-looking. Standard AmigaOS Workbench icons were plain and uninteresting: limited to four colours, having no standard size, and viewed from a straight-on perspective that left them looking two-dimensional.
The aim of NewIcons is to solve all these faults. Unlike a standard Workbench icon, which only includes palette index information and is thus at the mercy of the user's chosen Workbench palette, NewIcons icons are natively drawn in 32 colours (5-bit colour) and hold the actual RGB colour information in the icon file. A memory-resident program (called a Commodity in AmigaOS terminology) tries its best to adapt the icon's colours into the current Workbench screen palette.
NewIcons also establishes a standard icon size of 36×40 pixels, similar to those of Mac OS and Windows. The design guidelines recommend icons to be drawn at a more diagonal perspective, thus creating the illusion of three dimensions. The guidelines also strongly encourage the use of Workbench's "image" highlights, where a selected image changes its actual shape when clicked, instead of simply inverting its colours or becoming a darker shade. For example, a computer terminal could have its screen powered up, a pen could write letters on paper, or a robot symbolising a computer game could move around.
NewIcons also includes DefIcons, a package of ready-made icons which aims to provide a default icon image for all files that do not have their own associated icons (provided as
.info files in AmigaOS). DefIcons uses a scheme that actually examines the file's contents instead of simply looking at the filename extension to determine the file type. This approach is slower than the file extension system used by Microsoft Windows, but ultimately more accurate; a PNG image file with a .JPG extension will appear with a PNG-specific icon.