A compression technology called MRC (Mixed Raster Content) is used to minimize the size of PDF and PDF/A files.
Document image files are usually very large due to the background, which 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 color 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.
All this results in the image having a dark background with additional textures. The text appears blurred and difficult to read.
The MRC technology allows for better document appearance and up to 8-10 smaller file size than JPEG.