Highly Compressed (MRC) PDF Export

KB-Type:
Tips & How to Information
Version:
9.0, 11
Category:
Export

Definition

  • MRC = Mixed Raster Content
  • MRC = process of using image segmentation methods to improve the contrast resolution of a raster image composed of pixels.

Source: http://en.wikipedia.org/wiki/Mixed_raster_content

Benefits

MRC compression (in PDFs) achieves significantly better file compression without visible degradation of document representation. In the result the file size is significantly reduced: up to 10 times smaller compared to JPEG compression.

MRC compressed PDF documents save bandwidth and storage, that is why MRC compression is especially recommended to use when processing colour documents. Application users benefit from the combination of good visual quality with small file sizes - particularly useful for reading documents on mobile devices.

MRC Compression Scheme

The diagram illustrates the basic principle of MRC PDFs: different sections of a page are compressed with different compression algorithms. So for example

  • The black/white text layer might be compressed with CCITT4
  • Images with JPEG or JPEG2000

  • Document image files are usually very large due to the background, which is often makes up to 90% of the file size. The background may, however, be unnecessary in the resulting document. It is the text and pictures that are important.
  • The MRC compression technology allows locating the colour background and deleting it or compressing to a high degree. This leaves text and pictures against a white background contributing to smaller file size.
  • Picture objects (diagrams, graphs, logos, photos, drawings, stamps, signatures, etc.) are also slightly compressed, but only to an extent that doesn’t lower the quality.
  • The MRC technology analyzes the outlines of similar characters in the document, creates an average character template and uses it instead of a character itself. This leads to better readability, because some of the text defects are corrected, and the character outlines become more precise.
  • As a result, you get a smaller image which looks even better than before. The resulting document will have an unobtrusive bland background with fine text and pictures.
  • This “reconstruction” of the document can be useful when you have to deal with low quality images due to: bad lighting, out-of-focus photo, incorrect scanning/photo parameters, dark uncoated paper, or document dilapidation.

PDF Export Profiles in CLI Tool

In ABBYY CLI Tool the following four PDF export profiles are available:

  • Maximum Quality - the PDF (PDF/A) export will be optimized to receive the best quality of the resulting file.
  • Balanced (quality / file size) - the PDF (PDF/A) export will be balanced between the quality of the resulting file, its size and the time of processing.
  • Minimal Size - the PDF (PDF/A) export will be optimizied to receive the minimum size of the resulting file.
  • Maximum Speed - the PDF (PDF/A) export will be optimized to receive the highest speed of processing.

Illustration screenshot made on a Laptop (2012) Quad i7-3720QM, 2,6 GHz, Windows 7, 16 GB RAM, 64 bit; FineReader Engine 11 R1 - Std. sample files that are included in the sample that comes with the Windows SDK. Note: The CLI tool offers the the functionality via parameters, but without a GUI; speed and recognition results of course vary on the document type, recognition language, image quality and used hardware.

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