Mixed raster content (MRC) is a method for compressing images that contain both binary-compressible text and continuous-tone components, using
image segmentation
In digital image processing and computer vision, image segmentation is the process of partitioning a digital image into multiple image segments, also known as image regions or image objects (Set (mathematics), sets of pixels). The goal of segmen ...
methods to improve the level of compression and the quality of the rendered image.
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
Portable document format (PDF), standardized as ISO 32000, is a file format developed by Adobe Inc., Adobe in 1992 to present documents, including text formatting and images, in a manner independent of application software, computer hardware, ...
.
This allows for multiple images, and the instructions to properly render and reassemble them, to be stored within a single file.
Some
image scanner
An image scanner (often abbreviated to just scanner) is a device that optically scans images, printed text, handwriting, or an object and converts it to a digital image. The most common type of scanner used in the home and the office is the flatbe ...
s optionally support MRC when scanning to PDF. A typical manual states that without MRC, the image is generated in a single process, with text and graphics not distinguished. With MRC, separate processes are used for text, graphics, and other elements, producing clearer graphics and sharper text, at the price of slightly slower processing. MRC is recommended to optimise the scanning of documents with harder-to-read text or lower-quality graphics. MRC can also reduce the size of the scanned file,
though higher compression using
JBIG2
JBIG2 is an image compression standard for bi-level images, developed by the Joint Bi-level Image Experts Group. It is suitable for both lossless and lossy compression. According to a press release from the Group, in its lossless mode JBIG2 typ ...
can sometimes lead to character substitution errors in scanned documents.
File format
A form of MRC is defined by international standard bodies as
ISO/IEC
ISO/IEC JTC 1, entitled "Information technology", is a joint technical committee (JTC) of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). Its purpose is to develop, maintain and ...
16485, or
ITU
The International Telecommunication Union (ITU)In the other common languages of the ITU:
*
* is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established ...
recommendation T.44 (accessible free of charge). 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
JBIG2 is an image compression standard for bi-level images, developed by the Joint Bi-level Image Experts Group. It is suitable for both lossless and lossy compression. According to a press release from the Group, in its lossless mode JBIG2 typ ...
, while the images can be
JPEG
JPEG ( , short for Joint Photographic Experts Group and sometimes retroactively referred to as JPEG 1) is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degr ...
,
JBIG1, or run-length encoded color. The format is loosely based on JPEG, with a APP13 segment registered for this purpose.
It is not known whether this file format is actually used, as formats like DjVu and PDF have their own ways of defining layers and masks.
[
]
See also
*Binary image
A binary image is a digital image that consists of pixels that can have one of exactly two colors, usually black and white. Each pixel is stored as a single bit — i.e. either a 0 or 1.
A binary image can be stored in memory as a bitmap: a p ...
*
*Joint Photographic Experts Group
The Joint Photographic Experts Group (JPEG) is the joint committee between ISO/ IEC JTC 1/ SC 29 and ITU-T Study Group 16 that created and maintains the JPEG, JPEG 2000, JPEG XR, JPEG XT, JPEG XS, JPEG XL, and related digital image standard ...
(JPEG)
* Group 4 compression (MMR; T.6)
*JPEG 2000
JPEG 2000 (JP2) is an image compression standard and coding system. It was developed from 1997 to 2000 by a Joint Photographic Experts Group committee chaired by Touradj Ebrahimi (later the JPEG president), with the intention of superseding their ...
Compound image file format (JPM; T.805)
References
External links
Mixed Raster Content (MRC)
- Programme of Work Allocated to ISO/IEC JTC 1/SC 29/WG
JPEG
Computer graphics
T.44
ISO/IEC standards
{{compu-graphics-stub