You need to use these routines only if you wish to draw icons in your application's windows or to draw icons whose resource types are not recognized by the Menu Manager and Dialog Manager in menus and dialog boxes. To display an icon most effectively at a variety of sizes and bit depths, you should provide an icon family. You can then draw the appropriate member of the family for a given size and bit depth either by passing the family's resource ID to an Icon Utilities routine or by reading the family's icon resources into memory as an icon suite and passing the suite's handle to Icon Utilities routines. Icon Services provides icon data to multiple Mac OS clients, including the Finder, extensions and applications. Using Icon Services to obtain icon data means you can provide efficient icon caching and release memory when you don't need icon data any longer.
Icons are Appearance-compliant and appropriate to the active theme.