Mixed raster content

Mixed raster content (MRC) is a method for compressing images that contain both binary-compressible text and continuous-tone components, using image segmentation methods to improve the level of compression and the quality of the rendered image.[1] By separating the image into components with different compressibility characteristics, the most efficient and accurate compression algorithm for each component can be applied.

MRC-compressed images are typically packaged into a hybrid file format such as DjVu and sometimes PDF.[2] This allows for multiple images, and the instructions to properly render and reassemble them, to be stored within a single file.

File format
Mixed raster content
Magic number\xFF\xD8
Extended fromJPEG
StandardISO/IEC 16485:2000; ITU-T Recommendation T.44 (01/2005)

A form of MRC is defined by international standard bodies as ISO/IEC 16485 or ITU recommendation T.44. The latter version is freely accessible. It defines a file format with bilevel masks and two data layers in each "stripe" of the image. The mask can be encoded in ITU T.4, JBIG1, or JBIG2, while the image themselves can be JPEG, JBIG1, or run-length encoded color. The format is loosely based on JPEG, with a APP13 segment registered for this purpose.

It is unknown whether this file format sees actual use, as formats like DjVu and PDF has their own ways of defining layers and masks.[2]

See also

References
  1. de Queiroz, Ricardo; Buckley, Robert; Xu, Ming (28 December 1998). Mixed Raster Content (MRC) Model for Compound Image Compression (PDF). Visual Communications and Image Processing '99. ISBN 9780819431240. Retrieved 2012-08-03.
  2. "The MRC (Mixed Raster Content) Model and DjVu". web.archive.org. 16 December 2017.
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