Mixed Raster Content for Compound Image Compression

Mixed raster content (MRC) is described in the following report. It is a compression method which will be described here for compression of compound images (images containing both, continuous tone images and binary text) [1]. It uses a multi-layer, multi-resolution representation of a compound document. Instead of using a single algorithm, it uses multiple compression algorithms, including the ones specifically developed for text and images. So it can combine the best of new or existing algorithms and can provide various qualitycompression ratio tradeoffs. Also the problems faced by MRC compression are described along with its solutions and related topics. These topics include the problems with soft edges, edge sharpening, data-filling (with algorithms) [6], edge softening [4], resolution enhanced rendering (RER) [2] and optimizing block threshold segmentation for MRC compression [5], [9]. Also a comparison is made with JPEG standard [7], [8]. Tables and images after using different EE-5359 Pritesh Shah Spring 2009 (1000555858) Mixed Raster Content for Compound Image Compression 4 | P a g e compression techniques are shown. Most of the algorithms use the standard MRC with a 3layer representation which has some image processing overhead due to the management of multiple algorithms and the imaging model, and is also computationally expensive. A hybrid image coding scheme, shape primitive extraction and coding (SPEC) is also described which provides an accurate segmentation algorithm that separates the image into two classes of pixels: text/graphics and pictures [10], [11]. SPEC also provides a lossless coding scheme with low complexity algorithm for segmentation and good compression ratio along with excellent visual quality.