in the early days, the LZW compression algorithm used in GIF was a free algorithm developed by Compuserv. However, to the surprise of many software developers, the compression algorithm used in GIF files suddenly became the patent of Unisys.
According to Unisys, they have registered the W part of the LZW algorithm. If you want to develop a program to generate (or display) GIF files, you need to pay royalties to the company. Therefore, people began to seek a new technology to reduce the development cost.
PNG(Portable Network Graphics) [2] standard came into being under this background. On the one hand, it meets the needs of the market for fewer legal restrictions, on the other hand, it also brings fewer technical restrictions, such as the number of colors.