Acorn Sprite

File Format
Name	Acorn Sprite
Ontology	Electronic File Formats Graphics Acorn Sprite
Extension(s)	(none), .acorn

Acorn Sprite (also known as RISC OS Sprite) files are the native format for graphics on RISC OS systems. Traditionally, sprites were used to store all kinds of images. Since they support colour depths up to 32 bits per pixel it is possible to use this format to record photorealistic images (for example, from digital cameras) in this format, but improved support for compressed image formats (JPEG, PNG) in RISC OS means that sprites are typically used to hold images for application icons and screen dumps.

Format

A Sprite file consists of a 12-byte header, possibly followed by some extension data, followed by a sequence of images. Each image object begins with a 4-byte integer indicating its size.

The 4-byte integer at offset 0 is the number of images in the file.

The 4-byte integer at offset 4 is the offset of the first image, plus 4. It is usually 16, meaning 12.

The 4-byte integer at offset 8 is the file size, plus 4.

Identifiers

On RISC OS, Sprite files have a file type of ff9 (Sprite).

On other platforms, at least some applications use the filename extension .acorn, though it does not appear to be very common.

Software

• Konvertor
• Spritefile - a Python module for reading and writing Sprite files
• LibROSprite
• XnView (format named "ACORN")
• Deark

Sample files

• RISC OS Icons
• Arcade BBS: Sprite Picture files (These files may use Spark, ZIP, or other archive formats.)
• APDL DTP CD1, CD2, CD3
• ArtWorks ClipArt CD1

Links

• Documentation on Acorn Computers