Understanding the Mixed Raster Content (MRC) Format

The Mixed Raster Content (MRC) format was developed by the International Telecommunications Union as part of the ITU-T Recommendation T.44, and is defined in the proposed standard, RFC-2301, File Format for Internet Fax. The MRC model divides a page into strips and up to three layers: consisting of Mask, Foreground and Background layers. Each layer can be coded and compressed independently. Subsequently, these layers can be uncompressed and combined to restore the original image.

The advantage of the MRC model is that optimal compression methods can be selected for the various image and text components of documents, resulting in both high compression factors and high detail retention. Image and text components may be mixed on the same page.

A foreground layer contains color data for the text and line art, and may also contain photographic or continuous tone color data. The background layer generally contains low-resolution color image data, such as a background image, a wash or other pattern that would have text overlaid on it. The mask layer or the selector layer that controls the process of image regeneration contains binary image data that is high spatial resolution, such as text and line art. This layer is used for drawing the corresponding foreground layer where the selector value is 1 and drawing the corresponding background layer where the selector value is 0. (For example: a high-resolution color font can be represented using significantly less space, since the color information is stored at a lower resolution.)

LEADTOOLS offers the LEAD Mixed Raster Content object to handle mixed raster content files, expanding LEADTOOLS input/output functionality by adding support for color documents which contain mixed image and text components.