500 Byte Images: The Haiku Vector Icon Format | Leah Hanson
Haiku uses a custom vector image format to store icons. This is surprising both because most OSes consider bitmaps to be totally sufficient to represent icons and because there are plenty of vector graphics formats out this (e.g. SVG). The goal of the Haiku Vector Icon Format (HVIF) is to make vector icon files as small as possible. This allows Haiku to display icons as several sizes while still keeping the files small enough to fit into an inode (i.e., inside a file’s metadata). The goal of keeping the icons in the metadata is to reduce the disk reads needed to display a folder – it allows each file to only require one disk read to display.
This blog post examines the details of the HVIF format using a hex editor and the canonical parser’s source code. In the process of dissecting an example icon, I’ll also show you an optimization bug in the icon image editor.
HVIF is designed especially for the icons that appear when you look at the files in a folder.. This include the files on your desktop, which is just a special folder. Each file has an icon associated with it, based on the file type. While some OSes use thumbnails for PDFs and common image types, HVIF is focused only on the symbolic, abstract icons, not on file previews.
