JPG's are often used for web sites and email as they are generally smaller file sizes as they are lossy meaning that some image quality is lost when the JPG is compressed and saved. The resultant 'lossy' file means that quality can never be recovered. The JPG format is often used in digital camera memory cards. The JPG file is a great format as it often manages to compress files to 1/10 of the size of the original file which is especially good for saving on bandwidth.
JPG is a graphical file format for editing still images, it offers a symmetrical compression technique which is processor intensive and time consiming in both compression and decompression. JPEG is a joint standard of the International Telecommunications Union (ITU-T T.81) and the International Organization for Standardization (ISO 10918-1). JPEG involves a lossy compression mechanism using discrete cosine transform (DCT). Compression rates of 100:1 can be achieved, although the loss is noticeable at that level. Compression rates of 10:1 or 20:1 yield little degradation in image quality.
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The .pcx file extension was developed in the 1980s by the ZSoft Corporation. It has since been superseded by other image formats such as png, giff and jpeg. The file type is used rarely at present, however certain scanning devices still output to the .pcx format.
The PCX format was one of the first common bitmap image formats. A PCX file comprises of three elements: the header, image data and the 256 colour palette. PCX utiises a lossless compression technique. The compression technique used is not processor intensive which was an advantage at the time of development due to the relatively limited processing power of hardware in the 1980s.
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