tailieunhanh - Multimedia cho Joomla part 8

Mất dữ liệu và nén dữ liệu không mất dữ liệu Nén dữ liệu là một phần quan trọng của thế giới kỹ thuật số của chúng tôi. nén tập tin rất hữu ích vì nó giúp trong việc giảm tiêu thụ các nguồn tài nguyên đắt tiền như băng thông truyền tải và máy tính không gian đĩa cứng. | Chapter 4 Lossy and lossless data compression Data compression is an important part of our digital world. File compression is useful because it helps in reducing the consumption of expensive resources such as transmission bandwidth and computer hard disk space. Almost all digital images that we use on the web have been resized or compressed to some degree. When editing or saving files in popular software editing programs many options are provided to help optimize digital images. 77 Adding and Managing Image Content Lossy and lossless compression are two terms that describe the compression type of a file and whether or not the file retains all of the original data once compression and then decompression of that file has taken place. The preferred formats for digital web images such as JPEG and GIF all fall into one of the following compression types 1. Lossy A lossy data compression is one where the compression attempts to eliminate redundant or unnecessary file information. Generally once a file has been compressed the information that was lost during compression cannot be recovered again. Hence it is a degradable compression type and as the file is compressed and decompressed each time the quality of the file will suffer from generation loss. JPEG and MP3 files are good examples of formats that use lossy compression. 2. Lossless Lossless file compression makes use of data compression that retains every single bit of data that was in the original file before compression. Lossless compression is often used when an identical representation of the original data is required once a file has been compressed and then decompressed again. As an example it is used for the popular ZIP file format. Image formats such as PNG and GIF fall into the lossless compression type. For now it is not so important to go into any more detail on these compression types but the following image formats fall into both of these compression categories. It is possible to optimize your website .