JPEG
JPEG
1. Acronym for Joint Photographic Expert Group, the committee – a joint CCITT and ISO/IEC group – that works on the storage and transmission of still images and developed the ISO 10918 standard (see below).
2. The ISO 10918 standard, Digital Compression and Coding of Continuous Still Images, developed by JPEG for image compression of single digital images. The goal was to develop a general-purpose compression standard to meet the needs of almost all continuous-tone still-image applications, reducing either the bandwidth needed to transmit the image or the amount of memory needed to store it.
In its simplest mode of operation, JPEG can be thought of as compressing an image broken into 8 by 8 blocks of pixels. Each 8 by 8 block is processed by a pipeline of processes: discrete cosine transform to produce a representation of the sample as a collection of DCT coefficients, which are then quantized and entropy encoded (Huffman or arithmetic coding options exist). Decoding is the reverse of this process.
In addition, JPEG defines a lossless compression mode based on a simple predictive method. There is also a hierarchical encoding mode of operation that provides a pyramidal encoding at multiple resolutions, each differing by a factor of two in the horizontal direction, vertical direction, or both, from its adjacent encoding.
JPEG also makes provision for representing multiple-component images (color, spectral bands or channels), where each component consists of a rectangular array of samples.
See also MPEG.
1. Acronym for Joint Photographic Expert Group, the committee – a joint CCITT and ISO/IEC group – that works on the storage and transmission of still images and developed the ISO 10918 standard (see below).
2. The ISO 10918 standard, Digital Compression and Coding of Continuous Still Images, developed by JPEG for image compression of single digital images. The goal was to develop a general-purpose compression standard to meet the needs of almost all continuous-tone still-image applications, reducing either the bandwidth needed to transmit the image or the amount of memory needed to store it.
In its simplest mode of operation, JPEG can be thought of as compressing an image broken into 8 by 8 blocks of pixels. Each 8 by 8 block is processed by a pipeline of processes: discrete cosine transform to produce a representation of the sample as a collection of DCT coefficients, which are then quantized and entropy encoded (Huffman or arithmetic coding options exist). Decoding is the reverse of this process.
In addition, JPEG defines a lossless compression mode based on a simple predictive method. There is also a hierarchical encoding mode of operation that provides a pyramidal encoding at multiple resolutions, each differing by a factor of two in the horizontal direction, vertical direction, or both, from its adjacent encoding.
JPEG also makes provision for representing multiple-component images (color, spectral bands or channels), where each component consists of a rectangular array of samples.
See also MPEG.
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