A Brief Discussion on Compression Formats: Lossy vs. Lossless
Before we begin this brief discussion, there are a few simple terms about compression you should know.
- A bit (short for binary digit) is the smallest unit of measurement in a computer.
- Compression is the process of reducing the number of bits used in a file.
- Lossless compression is a data compression algorithm that allows you to reconstruct the original data from the compressed file.
- Lossy compression permanently eliminates redundant bits of data from the original file that are considered unimportant and imperceptible.
An easy way to understand the applications and importance of file compression is illustrated by photography. In today’s world, digital cameras are readily accessible and make many people fancy themselves amateur photographers. As a photographer, you take photos in a raw or uncompressed mode to have a high-quality image to play with later in editing software. These raw formats often take up large amounts of storage and must be compressed to reduce the file size and maintain quality. Lossless compression is a great tool that maintains an image’s quality and allows you to store and transmit files with ease, while still having access to the raw format.
Another example is seen when transferring music from a CD to a computer. We get to choose the bit rate, the compression, and the format we want the music to be in (music formats are often mp3, mp4, or WMA). A lower bit rate is good for playing music through one speaker, while higher bit rates have a better sound and can take advantage of surround sound or multi-direction speakers. Depending on the format and the purpose of the file, you can choose a compression of lossy or lossless. You should choose lossless compression on audio files if you want a perfect copy of your music and a lossy format if the file size is your priority.
There are a limitless amount of situations to compress files and they cannot all be covered in this “brief” discussion, but you should be aware that compression can greatly affect the usage and quality of the files you’re compressing.
TIFF and PDF Compression
While many of us are familiar with digital cameras and downloading music, today’s discussion is about the formatting options we have with the often ignored TIFF and PDF files we deal with on a daily basis. Most of us never knew that TIFFs have an option for lossy and lossless compression. You are able to compress these large TIFF files utilizing a lossless method called LZW or ZIP compression. This method retains all the raw data, unlike the lossy compression used with JPGs.
Why do we care? With music and photos, every time you save a lossy file you lose a little bit of it. This is because to view the file in a viewer or editor you have to take it back to a raw or uncompressed state. Then when you re-save it, you are taking your raw version and making a new file from it. The simple analogy is that when you make a copy of a copy, it may look acceptable at first, but each additional copy has a lower quality, more stray lines, and smaller text. The lossless format is able to store all the information and recreate the original raw file so no data is lost with each file download and saving. You can open and save a TIFF file an infinite amount of times without lowering the image quality because it is a lossless format.
The first reaction I normally get from a customer wanting to store large quantities of files is, “Let’s store everything in a PDF as to not lose any information”. What is often overlooked is when scanning and making a PDF, the PDF is made from our same TIFF or JPG and the PDF puts an additional wrapper on it, giving us some extra features. If you have chosen to store your documents in a PDF format you still need to be aware of how the image is being made that is going into the PDF for storage.
Be sure to consider the purpose of your data and decide which compression format will benefit you the most. There are pros and cons to each compression format and depending on the file type, you will have more success choosing one over the other.
Author: Brian Miller - Senior Solutions Architect at DoxTek
Did you like this article? Share it!
For more information contact the DoxTek Marketing Department