JPEG is an image compression standard that was developed by the Joint Photographic Experts Group committee in 1992 for the storage and transmission of a wide variety of still graphics image formats. It is designed for compressing either full-color or gray-scale digital images of continuous-tone quality.
It offers both a lossy and lossless compression alternative. The former occurs when a mathematical process called discrete cosine transform (DCT) is invoked that utilizes an 8 x 8 frame of pixels and yields a substantial compression. This process produces an image with some loss of detail that may not necessarily be detectable to the human eye. The actual amount of loss depends upon the compression ratio selected. In contrast, the lossless compression alternative achieves complete fidelity to the source image because the sampling area or frame is 2 x 2 pixels, three of which are aligned along different axes with respect to the fourth. The compression ratio is user controlled and limited to either 2:1 or 3:1.