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Maximum compression for e-books without quality loss — up to 5-30% (Lossless)! Full compatible with original formats. The document is reduced by repacking the contents with a stronger compression algorithm. It uses 2 programs and selects the best result: ECT (Efficient Compression Tool), AdvanceCOMP. Compression mode: good (faster) or best (slowly). Batch processing of files (drag-n-drop). Program optimizes your file to new one with «_optimized» name ending (source file will remain intact). Output files have their timestamps/permissions set to match those of their inputs. It saves quality of all pictures inside your ebooks. ePub is a free and open e-book standard by the International Digital Publishing Forum (IDPF). FictionBook (FB3) is an open XML-based e-book format.

Features:
— Maximum compression for e-book files without quality loss.
— Full compatible with original format.
— Supported formats: Epub, Fb3, Zip, txt.zip, fb2.zip, rtf.zip, fbz, cbz.
— Batch processing of files (drag-n-drop).
— Compression mode: fast (faster), normal, good or best (slowly).
— Compression of graphic files/images inside e-books without loss in quality (Lossless) up to 5-30%!
— Option «Preserve file attributes (time stamps, file access rights, etc.)».
— You can set «Run in background (without console output)» or uncheck it for manual process control.
— You can set «Low CPU usage (only 2 threads)» or uncheck it for best perfomance.

Used programs:
ECT (Efficient Compression Tool) (c) Felix Hanau — https://github.com/fhanau/Efficient-Compression-Tool
AdvanceCOMP (c) Andrea Mazzoleni — http://www.advancemame.it

Files have the extension .epub. It is designed for reflowable content, meaning that the text display can be optimized for the particular display device. The feature of ePub, especially compared with Word and PDF formats, the content in an ePub book is not pre-formatted as fixed book pages. When a reader device displays the content of an ePub book, it formats the content into pages according to the display size and text font. So when you are reading an ePub book, all you have to do is only flipping the pages. You don’t have to zooming or panning the window to view the page parts out of the displayed area.

EPUB is a straightforward format. An EPUB file (extension: .epub) is simply a ZIP archive that contains what is in effect an entire website, including HTML files, all necessary images, CSS style sheets and other assets, plus additional structure and information (“metadata”) that makes the content able to be reliably consumed from beginning to end by any application or device that’s compatible with the EPUB specifications (“EPUB reading systems” or just “reading systems” for short).

EPUB 3 is the latest version of EPUB. EPUB 3 is based on the latest HTML5 standard, which means EPUB publications can now contain video, audio, and interactivity – just like websites in modern browsers.

An EPUB publication’s content is by default reflowable and most reading systems dynamically paginate that content. Adapting content display to the screens rather than forcing the reader to pan and zoom around pre-formatted content (and, more generally, making content accessible to different modes of consumption) is one of the key characteristics that distinguishes EPUB from PDF, a portable document format designed to represent print-replica content. But EPUB 3 can also, like PDF, represent fixed-layout, pre-paginated content. This can be useful for certain kinds of highly-designed content (illustrated children’s books, digital magazines, etc.) that are designed to be consumed only on a larger-screen device, such as a tablet.

— Manifest – an EPUB publication contains a data structure detailing all of its constituent resources – in effect, a formal and complete “packing list”.
— Defined reading order – an EPUB publication has a “spine” that determines a start-to-end reading order for its top-level content items (though nothing requires that the publication to be consumed in that order).
— Standardized table of contents and related navigational structures, including the ability to define links into content fragments down to the sentence or word level.
— Metadata – publication and item level information about the publication and its components.
— XHTML – the HTML content in an EPUB publication must use the XML-based serialization of HTML5, which makes it directly manipulable by XML tools.
— Media Overlays – Well-defined publication-wide text+audio synchronization (an EPUB publication can be both an eBook and audio book).
— Core Media Types (such as image and audio formats) and minimum CSS features are well-defined, along with a requirement for fallbacks when non-standard content types are used. This enables more reliable processing of EPUB publications, especially when distributed indirectly, than arbitrary websites which may use less standard content types without fallbacks and bleeding-edge CSS constructs that may not be universally supported.

FictionBook is an open XML-based e-book format which originated and gained popularity in Russia. FictionBook files have the .fb3 filename extension. Readers also support ZIP-compressed FictionBook files (.fb3, .fb2.zip or .fbz)

FB3: FictionBook v.3
Open eBook format, epub replacement/addition (depends on how you use it).

The fb3 file is a totally new redesign of fb2 object format.

The main differences between fb2 and fb3 are:
basically, FB3 file object is a zip-archive, where meta-data, images and text are packaged as discrete files;
meta-information is stored in the distinct file, whereas the body of the book and footnotes – into the other;
all the images are being extracted from XML and are actually ordinary files in the archive.

The format is being developed in order to fulfill the growing requirements to the formatting of the books text and the possibilities of its cataloging. The modern condition of the standards and technologies allows, in addition to the basic advancement of the tags set, to conform the format to the compatibility with the most successful and perspective groundworks.

FB3 — format development.
In the new specification, the FictionBook format is a zip-archive in which metadata, images and text are stored as separate files. The requirements for the format of the zip-file and the agreement on its organization are specified in the ECMA-376 standard , which defines Open XML.

A number of improvements related to formatting (discharging, underlining) were made and a new object was added — “block” — which decorates an arbitrary fragment of the book in the form of a quadrangle and is capable of being embedded in text with flow. Added support for numbered and bulleted lists.

FB3 is distributed under a free license and is open source, so all utilities are available to publishers and users: converters, cloud editors, readers. The current format version , reader and editor can be found in the project repository on GitHub.

For reading e-books, you can use the AlReaderX, FBReader, Calibre, Ice Book Reader etc.

CBZ — A comic book archive or comic book reader file (also called sequential image file) is a type of archive file for the purpose of sequential viewing of images, commonly for comic books. The idea was made popular by the CDisplay sequential image viewer, since then, many viewers for different platforms have been created. Comic book archive files mainly consist of a series of image files with specific naming, typically PNG or JPEG files, stored as a single archive file.

Current file has its own status in the list: «running», «done» and «saved space».
Full stats:
1. Number of optimized files (total and current session).
2. Files in the queue (quantity).
3. Saved disk space (Mb) total and for each file in the list.
(You need to save files «ressize.txt» and «resnumbers.txt» before updating, if you want to save the overall statistics («Total»)).

Size (7z): 3 Mb