PDF is a file format developed by Adobe Systems for representing documents in a manner that is separate from the original operating system, application or hardware from where it was originally created. A PDF file can be any length, contain any number of fonts and images and is designed to enable the creation and transfer of printer-ready output.
Each PDF file encapsulates a complete description of a 2D document (and, with the advent of Acrobat 3D, embedded 3D documents) that includes the text, fonts, images and 2D vector graphics that compose the document. They do not encode information that is specific to the application software, hardware, or operating system used to create or view the document.
The GIF file format is a type of bitmap image and has become popular due to the growth of the internet. This file format supports up to 8 bits per pixel therefore giving an image the ability to contain 256 distinct colours chosen from the 24-bit RGB colour space. It also supports animations and whenever you see a logo or other sharp edged line art then you are probably dealing with the GIF format. It uses the lossless data compression technique which reduces the file size without any impact on the quality.
The GIF file format was invented by Compuserve for their online service, but they made the specifications publicly available. GIFs are able to hold multiple bitmaps of up to 256 colors each, using LZW (Lempel Zev Welch - a simple form of file compression that removes inefficiencies in the data storage without losing data or distorting the image) compressed raster data to minimize file sizes. The idea is to lessen the amount of colours in a GIF image to the minimum number necessary and to therefore remove stray colors that are not required to represent the image. A GIF graphic is unable to have more than 256 colors but it can have fewer colors, down to the minimum of two (black and white). Images with fewer colors will compress more efficiently under LZW compression.
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