What Is Compression?

What Is Compression?

Compression is the process of reducing the size of a file by encoding its data information more efficiently. By doing this, the result is a reduction in the number of bits and bytes used to store the information. In effect, a smaller file size is generated in order to achieve a faster transmission of electronic files and a smaller space required for its downloading.

How does Compression work?

When you have a file containing text, there can be repetitive single words, word combination and phrases that use up storage space unproductively. There can be media such as high-tech graphical images in it whose data information occupies too much space. To reduce inefficiency electronically, you can compress the document.
Compression is done by using compression algorithm (formulae) that rearrange and reorganize data information so that it can be stored more economically. By encoding information, data can be stored using fewer bits. This is done by using a compression/decompression program that alters the structure of the data temporarily for transporting, reformatting, archiving, saving, etc.
Compression, when at work, reduces information by using different and more efficient ways of representing the information. Methods may include simply removing space characters, using a single character to identify a string of repeated characters, or substituting smaller bit sequences for recurring characters. Some compression algorithms delete information altogether to achieve a smaller file size. Depending on the algorithm used, files can be adequately or greatly reduced from its original size.

Lossless Compression and Lossy Compression

Lossless Compression

It is a type of Compression that can reduce files without a loss of information in the process. The original file can be recreated exactly when uncompressed. To achieve this, algorithms create reference points (substitution characters) for things such as textual patterns, store them in a catalogue and send them along with the smaller encoded file. When uncompressed, the file is "re-generated" by using those documented reference points to re-substitute the original information.
Lossless Compression is ideal for documents containing text and numerical data where any loss of textual information cannot be tolerated. ZIP compression, for instance, is a Lossless Compression that detects patterns and replaces them with a single character. Another example, LZW compression (Abraham Lempel, Jakob Ziv and Terry Welch-creators of LZW compression), works best for files containing lots of repetitive data.

Lossy Compression

On the other hand, Lossy Compression reduces the size of a file by eliminating bits of information. It permanently deletes any unnecessary data. This compression is usually used with images, audio and graphics where a loss of quality is affordable. However, the original file cannot be retained.
For instance, in an image containing a green landscape with a blue sky, all the different and slight shades of blue and green are eliminated with compression. This essential nature of the data is not lost, the essential colours are still there. One popular example of Lossy Compression is JPEG compression (Joint Photographic Experts Group) that is suitable for grayscale or colour images.

Compression and the PDF

When looking at compression in terms of the PDF, it's easy to see how the format makes use of compression methods. Compression aids PDF functions such as:

• Transmitting large file sizes
• Keeping the original appearance of a document
• Transferring files with multiple pages
• Formatting multi-media graphics

The main uses of the PDF make compression a necessity. Thus, when you create your PDF's using Investintech software, you are given a variety of compression options with Sonic 1.2 PDF Creator. Choose from compression options, like those mentioned above, for colour, monochrome or grayscale images. Investintech ensures that your PDF's have the compact size you need to efficiently work with them.

Compression utilities:

1. WinZip

WinZip, the original and most popular compression utility for Windows, is a powerful and easy-to-use tool that zips and unzips files quickly to conserve disk space and greatly reduce email transmission time. WinZip 12.1 introduces the Zipx format creating the smallest Zip files ever. You can even compress JPEG files by 20-25% without losing photo quality and manage and share digital photos more easily. WinZip integrates with Windows seamlessly, opens RAR, 7Z and other file types and offers AES encryption to keep files secure. Use its award-winning classic view or it's intuitive Wizard that helps new users accomplish basic zipping and unzipping tasks quickly and easily. You can let WinZip select the best compression method for each file type maximum advantage of powerful advanced compression methods that create even smaller Zip files. A familiar Explorer-style view makes it easy to navigate large, multi-folder archives and the thumbnail view lets you see images in the main WinZip window quickly. WinZip is available in Standard or Pro. WinZip 12 Pro offers a new Zip from camera feature that make it easy to import, rotate, resize and view digital photos, plus the WinZip Job Wizard that allows you to automate repetitive zipping tasks, back up data easily, archive important documents and distribute information. You can move valuable data off site with WinZip's FTP upload functionality or burn a Zip-related tasks directly from Windows Explorer without opening a separate WinZip window.

2. PKZip

Simple and uncluttered, that is PKZip. When you launch it, you see just a four-item text menu and three icons. The icons, called New, Open, and Wizard, handle most compression jobs, and the text menu are smart too. PKZip's compression settings are vast, including one called Extra, which compresses files to the maximum (but which also makes them zip and unzip a bit more slowly). PKZip performs solidly. At maximum compression, it produced files just a few hundred bytes larger than the ones WinZip creates. On a high-end machine, PKZip compressed a mixture of ASCII and binary files slightly faster than WinZip, though on a low-end Pentium system, it compressed files lightly slower.
Unlike PKZip, for example, WinZip lets you drag and drop any file from the ZIP archive window into an application and then view and edit its contents. PKZip's interface works, but WinZip's seamless power puts it over the top. WinZip and PKZip both cancelled each other out in speed on low and high-end systems, and their compressed file sizes were virtually identical. You will get roughly the same performance from either utility, so it's better to concentrate on their features.
PKZip for Windows is a worthy challenger, but it needs a little bit more oomph to dethrone the champ. Whether it's UI touches or file management, WinZip's just a little bit better. Performance is about the same, but feature-for-feature, WinZip gives you more. Feature-to-feature, WinZip takes the cake.

3. WinRAR

a. What is a RAR file?

RAR is the native format of WinRAR archiver. Like other archives, RAR files are data containers, they store one or several files in the compressed form. After you downloaded RAR file from Internet, you need to unpack its contents in order to use it.

b. Difference between RAR and ZIP

Comparing to ZIP file format, RAR provides a number of advanced features:

• More convenient multipart (multivolume) archives.
• Tight compression including special solid.
• Multimedia and text modes.
• Strong AES-128 encryption.
• Recovery records helping to repair an archive even in case of physical data damage.
• Unicode support to process non-English file names and a lot more.

c. How to handle RAR files?

WinRAR provides the complete support for RAR files, so you may both create and unpack them. If you installed WinRAR on your computer and downloaded RAR file from internet, you may double click on RAR file icon to open it in WinRAR, select all files, press "Extract To" button, enter a destination path and press "OK". Another way is to click on the RAR file in Explorer using the right mouse button. If your enabled "Shell integration" option when installing WinRAR, the file context menu will contain "Extract To ... "item.
Some RAR files can be parts of multi-volume sequences. In WinRAR, you can split a huge archive to a few smaller files, which are called volumes. They may have extensions .rar (the first volume), .r00, .r01, ..., or .part1.rar (the first volume), .part2.rar, ..., etc. If you need to unpack volumes, places all them to the same folder and start extraction from the first volume.
WinRAR is a competing product to WinZip; both products compresses/decompresses and archive files. Files compressed with WinRAR typically have the .rar extension, as opposed to .zip for WinZip archives. WinRAR can also create and decompress a WinZip archived file.
WinRAR can create archives in multiple parts; that is, it not only can compress a file but can split it up into smaller parts. In WinZip, this is called a split Zip file; in WinRAR, it's called a multipart or multivolume archive. When this is done, the smaller RAR files are given the following extensions, in this order: .rar, .r00, .r01, and so forth. To decompress a multipart archive, make sure all the component files are in the same directory and double-click the .rar file. WinRAR will automatically find all the other files without you having to select them, and assemble the final decompressed file from them.