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JPEG ( )〔(【引用サイトリンク】title=Definition of "JPEG" )〕 is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality. JPEG compression is used in a number of image file formats. JPEG/Exif is the most common image format used by digital cameras and other photographic image capture devices; along with JPEG/JFIF, it is the most common format for storing and transmitting photographic images on the World Wide Web. These format variations are often not distinguished, and are simply called JPEG. The term "JPEG" is an acronym for the Joint Photographic Experts Group, which created the standard. The MIME media type for JPEG is ''image/jpeg'', except in older Internet Explorer versions, which provides a MIME type of ''image/pjpeg'' when uploading JPEG images.〔(MIME Type Detection in Internet Explorer: Uploaded MIME Types ) (msdn.microsoft.com)〕 JPEG files usually have a filename extension of ''.jpg'' or ''.jpeg''. JPEG/JFIF supports a maximum image size of 65,535×65,535 pixels,〔(JPEG File Layout and Format )〕 hence up to 4 gigapixels (for an aspect ratio of 1:1). ==The JPEG standard== "JPEG" stands for Joint Photographic Experts Group, the name of the committee that created the JPEG standard and also other still picture coding standards. The "Joint" stood for ISO TC97 WG8 and CCITT SGVIII. In 1987 ISO TC 97 became ISO/IEC JTC1 and in 1992 CCITT became ITU-T. Currently on the JTC1 side JPEG is one of two sub-groups of ISO/IEC Joint Technical Committee 1, Subcommittee 29, Working Group 1 (ISO/IEC JTC 1/SC 29/WG 1) – titled as ''Coding of still pictures''.〔(【引用サイトリンク】title=Programme of Work, (Allocated to SC 29/WG 1) )〕〔(【引用サイトリンク】title=JTC 1/SC 29 – Coding of audio, picture, multimedia and hypermedia information )〕 On the ITU-T side ITU-T SG16 is the respective body. The original JPEG group was organized in 1986,〔(【引用サイトリンク】 title=Joint Photographic Experts Group, JPEG Homepage )〕 issuing the first JPEG standard in 1992, which was approved in September 1992 as ITU-T Recommendation T.81〔(【引用サイトリンク】title=T.81 : Information technology – Digital compression and coding of continuous-tone still images – Requirements and guidelines )〕 and in 1994 as ISO/IEC 10918-1. The JPEG standard specifies the codec, which defines how an image is compressed into a stream of bytes and decompressed back into an image, but not the file format used to contain that stream.〔 〕 The Exif and JFIF standards define the commonly used file formats for interchange of JPEG-compressed images. JPEG standards are formally named as ''Information technology – Digital compression and coding of continuous-tone still images''. ISO/IEC 10918 consists of the following parts: Ecma International TR/98 specifies the JPEG File Interchange Format (JFIF); the first edition was published in June 2009. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「JPEG」の詳細全文を読む スポンサード リンク
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