PNG pronounced ping is a format for storing bitmapped (raster) images on computers. It was created originally to replace the GIF file format when it was announced that the companies who created the GIF format wanted royalties. PNG uses indexed colors and lossless compression (like a .GIF file), but without those copyright limitations; it cannot be animated like a GIF image.
PNG images are in many ways better than .GIF as they also include an 8-bit transparency channel, which allows the colors in the image to fade from opaque to transparent; GIF images only support fully opaque or fully transparent pixels. PNG supports palettes of 24-bit RGB colors, RGB images or greyscale or RGB images. PNG was intended to be able to transfer images on the Internet, not professional graphics, and so does not support other colour spaces (such as CMYK).
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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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