Difference Between Lossy and Lossless Compression

The main difference between lossy and lossless compression is that the lossy compression reduces the quality of the original data while the lossless compression does not reduce the quality of the original data.

Computers store and send data for transmission in the form of bits. Data can consume more storage space. Data compression is an alternative to this issue. It allows modifying the bit structure of data in a way that consumes a minimum amount of space on the disk. It also helps to send data or files quickly over the network. Data compression is also known as source coding or bit rate reduction. There are two types of data compression techniques called lossy compression and lossless compression.  The main difference between lossy and lossless compression lies in the quality. Lossy compression causes quality reduction while lossless compression does not cause quality reduction.

Key Areas Covered

1. What is Lossy Compression
     – Definition, Functionality
2. What is Lossless Compression
     – Definition, Functionality
3. Difference Between Lossy and Lossless Compression
     – Comparison of Key Differences

Key Terms

Data Compression, Lossy Compression, Lossless Compression

What is Lossy Compression

Loosy compression is a data compression technique that uses partial data discarding and inexact approximation to represent the data. It helps to reduce the size of the data so that it is easier to store, handle and transmit. However, it causes some data loss and reduction in the quality of the original data.

Figure 1: JPEG Compression

Lossy compression is commonly used to compress multimedia data such as audio, video, and images. It is used in applications such as streaming media and internet telephony. Even though it causes data loss and degradation, lossy compression is used in data communication to reduce transmission time and to reduce storage space.

What is Lossless Compression

Lossless compression reduces the original data size but it does not minimize the quality. Lossless compression rewrites the original file data in an efficient manner. Lossless compression does not reduce the quality of the original data. Therefore, the resulting file has some amount of storage.

Figure 2: Photo saved using Lossless Compression

Lossless data compression is used in ZIP files format and in GNU tool gzip. Some image file formats such as PNG or GIF only uses lossless compression. It is also used for text and data files. Lossless audio formats are used for archiving or production purposes.

Difference Between Lossy and Lossless Compression

Definition

Loosy compression permits reconstruction only of an approximation of the original data, though usually with improved compression rates. Lossless compression is a class of data compression that allows the original data to be perfectly reconstructed from the compressed data.

Synonyms

Irreversible compression is another name for lossy compression while lossless compression is also called reversible data compression.

Quality

While lossy compression reduces the quality, lossless compression does not reduce the quality.

Data Reduction

Data reduction in lossy compression is higher than in lossless compression.

Resulting File

In lossy compression, a file smaller than the original file is produced. In lossless compression, the resultant file is not as small as the lossy compression’s resultant file.

Usage

Lossy compression is commonly used to compress multimedia data such as audio (MP3), video and image (JPEG) files. Lossless compression is used for text, data files, audio, and images.

Conclusion

Data compression helps to send data over the network quickly and it also reduce the required physical storage area. Lossy and lossless compression are two techniques that reduce data size to store and transmit efficiently. The difference between lossy and lossless compression is that the lossy compression reduces the quality of the original data while the lossless compression does not reduce the quality of the original data.

Reference:

1. “Lossy Compression.” Wikipedia, Wikimedia Foundation, 15 Aug. 2018, Available here.
2. “Lossless Compression.” Wikipedia, Wikimedia Foundation, 18 Aug. 2018, Available here.

Image Courtesy:

1. “JPEG compression Example” By JJ Harrison (CC BY-SA 3.0) via Commons Wikimedia
2. “Ruby-Lossless” By 0x0077BE – Own work (CC0) via Commons Wikimedia