What is lossy compression

Posted on: September 23rd, 2022
By: Tadeo Lemus

Have you ever wondered how music or videos can be stored and transferred digitally without taking up too much space? Lossy compression is the answer.

Lossy compression is a data encoding technique that reduces the size of a digital file by removing information that is considered unnecessary. This technique dramatically reduces the size of digital files by sacrificing some quality to improve efficiency.

It is used to compress images and audio files, allowing them to be stored and transmitted more efficiently. However, this compression’s downside is that it can’t keep all the details in the picture, so some information gets lost.

Even though some information may be lost during the process, the overall quality of the file is usually still acceptable for most purposes.

Want to learn more? Keep reading.

How does lossy compression work

Lossy compression works by discarding some of the data in the file that is considered less important. By carefully balancing what data to keep and what to discard, lossy compression can achieve significant reductions in file size without causing too much degradation in quality. 

The lossy compression process involves applying mathematical algorithms that reduce the size of a digital image, audio, or video file by removing certain details that are not essential for human perception. 

For example, when compressing an image, lossy compression algorithms will focus on preserving the details of the image while sacrificing things like color depth and overall fidelity.

Application of lossy compression

In general, lossy compression is most effective on files containing a lot of redundant data. This includes files like images and audio, where some information can be removed without affecting the overall quality.

One common type of lossy compression for digital images is JPEG compression. JPEG image compression removes data not visible to the human eye, such as the color values of individual pixels. Using this method, you can reduce the file size by 90%, making it ideal for compressing digital images.

Lossy compression can also be used for audio data. MP3 is a popular type of lossy audio compression. MP3 compression works by discarding audio data that the human ear is not able to perceive. Consequently, file sizes are smaller, but there is some loss of audio quality.

Lossy compression is not suitable for all applications,  and you should always consider whether it is appropriate for your needs before using it.

The difference between lossless and lossy compression

In lossy compression, some data is removed from the file in order to reduce its size, while lossless compression reduces the file size without losing any data. 

Lossy compression is typically used for images and audio files. In contrast, lossless compression is used for text files and other data types that can be accurately reproduced with no loss of information.

Lossy compression is ideal for files that will be viewed or heard on devices with limited storage or bandwidth, such as smartphones or low-end MP3 players.

On the other hand, lossless compression does not sacrifice any quality to reduce file size. It is, therefore, ideal for files that need exact copies of the original, such as text documents or software code. 

Lossy compression can result in some loss of quality, but it can also dramatically reduce file sizes. For example, a lossy compressed image might have some JPEG artifacts or blurring, but the file size would be much smaller than if it were uncompressed. 

However, lossless compression generally results in only a small reduction in file size, so it is not as well suited for files that need to be very small, such as images or music files.

Different algorithms used in lossy compression

There are a variety of algorithms used in lossy compression, each with its own strengths and weaknesses. 

Wavelet transform

A wavelet transform is a particular type of mathematical transformation used to reduce the amount of data in a signal. Wavelet transforms work by dividing a signal into a series of smaller, more manageable pieces and then transforming each piece using a specific algorithm.

This makes the file easier to compress and, in some cases, can improve image quality. This process can be repeated multiple times, resulting in a signal significantly reduced in size without any significant loss in quality.

Discrete cosine transform

The discrete cosine transform (DCT) is a lossy compression technique often used in image and video compression. The DCT can be thought of as a way of representing an image or video signal in terms of a set of sinusoidal waveforms. The DCT coefficients represent the amplitude of the waveforms at different frequencies. 

The DCT can be used to compress any image or video by discarding the high-frequency components, which are mostly less visible to the human eye. The resulting compressed signal can be decompressed using the inverse DCT transform. 

Fractal compression

Fractal compression is a lossy compression technique for storing digital images. The idea behind fractal compression is that an image can be meaningfully represented by a small number of self-similar “fractal” patterns. 

By finding and storing these patterns, it is possible to reconstruct the image with reasonable fidelity while still achieving significant compression. In practice, fractal compression is often used in conjunction with other lossy techniques such as JPEG or MPEG to improve the compression ratio further. 

While fractal compression can be computationally intensive, the resulting files can be very small, making it an appealing option for applications with limited storage space.

The risks of lossy compression

While lossy compression can effectively reduce file size, some risks are also associated with it.

One potential issue is that once data is removed, it cannot be recovered. This means that if you compress a file using a lossy format, you will not be able to restore the original quality, no matter how many times you decompress and re-compress it.

Additionally, lossy compression can sometimes introduce artifacts. Artifacts are typically small blocks or pixels that are different from the surrounding pixels. These artifacts can make the image appear blocky or fuzzy. 

In addition, audio files that have been lossy compressed can sound distorted or have a lower quality than uncompressed files.

When to use lossy compression

There are a few times when you might want to use lossy compression. One is when you have a lot of content that you want to store but don’t need the quality of the content to be perfect.

Another time is when you’re working with images and want to save space on your hard drive. Lossy compression can help reduce the size of your files without sacrificing too much quality.

For example, if you have a lot of music files that you want to store on your computer, you can use lossy compression to save space. The quality of the music won’t be as good as it would be if you used a lossless compression method, but it will still sound good.

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