Full Name	Interchange File Format
Format ID	IG_FORMAT_IFF = 18
File Extension(s)	*.iff
Data Type	Raster Image
Data Encoding	Binary
ImageGear Multipage Support	Yes
ImageGear Alpha Channel Support	No
ImageGear Platforms Support	WIN32, WIN64, Unix, Unix64, .NET, .NET64, MAC

ImageGear Supported Versions:

• Version 1, 1985

ImageGear Supported Features:

• IG_FLTR_DETECTSUPPORT - autodetection
• IG_FLTR_MPAGEREADPSUPPORT - multi-page file reading
• IG_FLTR_PAGEINSERTSUPPORT - single-page file writing
• IG_FLTR_PAGEREADSUPPORT - single page file reading

ImageGear Read Support:

• IG_COMPRESSION_NONE:
  • Indexed RGB: 1, 4, 8 bpp;
  • RGB: 24 bpp
• IG_COMPRESSION_RLE:
  • Indexed RGB: 1, 4, 8 bpp;
  • RGB: 24 bpp

ImageGear Write Support:

• IG_COMPRESSION_NONE:
  • Indexed RGB: 1, 4, 8 bpp;
  • RGB: 24 bpp
• IG_COMPRESSION_RLE:
  • Indexed RGB: 1, 4, 8 bpp;
  • RGB: 24 bpp

ImageGear Filter Control Parameters:

None

Comments:

This type of file format is referred to as a "wrapper" because it can include any type of data that is encoded in any manner.

The basic organization of the IFF file format utilizes storage structures known as "chunks". A chunk is a block of data that contains its own header (that identifies the chunk size and type). This makes it easy for an IFF viewer to identify chunks and to skip over the ones that are not necessary.

The Header Chunk contains 17 fields, including the size of the header chunk, the identification of the chunk as a header, the size and origin of the image, data encoding (yes or no), and aspect ratio.

A "CMG Chunk" may follow, containing data specific to Amiga display hardware.

A "CMAP Chunk" contains the RGB palette for the image.

The "Body Chunk" (also called the ILBM or "interleaved bitmap"), is the image data itself. It is stored in an "interleaved" format, by bit plane. Interleaving allows for data with different resolutions to be neatly stored together. The data may be uncompressed or compressed using an RLE scheme. See RLE section for more information.

References Used

Brown, C. Wayne, and Barry J. Shepherd. Graphics File Formats: Reference and Guide. Greenwich, CT.: Manning Publications, 1992.

Kay, David C. and John R. Levine. Graphics File Formats. Windcrest Books, 1992.

Murray, James D. and William vanRyper. Encyclopedia of Graphics File Formats. Sebastopol, CA: O'Reilly & Associates, Inc., 1994.