Compression frees disk space and saves transmission time. Compression is carried out by a program that applies a formula or algorithm that determines the manner of compression or decompression. The quality of the result of the compression process depends on the algorithm used. The size of the resulting PDF file depends on how well the compression techniques are used, how the data is described, and also the number of fonts, forms, images and multimedia contained in the file.
Two Ways Algorithms Compress PDF Files
PDF uses different compression algorithms to reduce their size to almost half the size of an equivalent Post Script file. algorithms compress PDF files in two ways: by using a lossy compression method and by using a lossless compression method. When a lossy compression is used, a higher compression ration is achieved at the cost of permanent loss of some of the data in the content. However, since the human eye is not sensitive to small changes in brightness, the difference in image quality creates no noticeable change in the image. When a lossless compression algorithm is used, the compression ration is much less than in the case of lossy compression, but the image does not suffer any quality loss. On decompression of the compressed image, you get the original image.
Zip is suitable for images with large areas of single colors or repeating patterns and for similar black-and-white images. Although it is a lossless method, using 4-bit ZIP compression with 8-bit data can cause changes in the quality. CCITT is a lossless method. CCITT Group 4 is a good compression method for all monochrome images and CCITT Group 3 compresses monochrome images in singles. RLE is a lossless compression method that is more suitable for images with large areas of solid black or white. Jpeg is a lossy compression method suitable for grayscale and color natural, photographic-like, true-color images. It tires to shrink the size of files with the minimum loss of data. Since it eliminates data, it is able to achieve a much higher compression ratio than zip compression method.