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Image compression is a type of data compression applied to digital images, to reduce their cost for storage or transmission. Algorithms may take advantage of visual perception and the statistical properties of image data to provide superior results compared with generic data compression methods which are used for other digital data.
The JPEG filename extension is JPG or JPEG. Nearly every digital camera can save images in the JPEG format, which supports eight-bit grayscale images and 24-bit color images (eight bits each for red, green, and blue). JPEG applies lossy compression to images, which can result in a significant reduction of the file size.
Continuously varied JPEG compression (between Q=100 and Q=1) for an abdominal CT scan. JPEG (/ ˈ dʒ eɪ p ɛ ɡ / JAY-peg, short for Joint Photographic Experts Group and sometimes retroactively referred to as JPEG 1) [2] [3] is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography.
Examples of algorithms for this task include New Edge-Directed Interpolation (NEDI), [1] [2] Edge-Guided Image Interpolation (EGGI), [3] Iterative Curvature-Based Interpolation (ICBI), [citation needed] and Directional Cubic Convolution Interpolation (DCCI). [4] A study found that DCCI had the best scores in PSNR and SSIM on a series of test ...
Image scaling can be interpreted as a form of image resampling or image reconstruction from the view of the Nyquist sampling theorem.According to the theorem, downsampling to a smaller image from a higher-resolution original can only be carried out after applying a suitable 2D anti-aliasing filter to prevent aliasing artifacts.
Due to typical file system design, the amount of space allocated for a file is usually larger than the size of the file's data – resulting in a relatively small amount of storage space for each file, called slack space or internal fragmentation, that is not available for other files but is not used for data in the file to which it belongs.
The internationally recommended unit symbol for the kilobyte is kB. [ 1 ] However, in some areas of information technology , particularly in reference to random-access memory capacity, kilobyte instead typically refers to 1024 (2 10 ) bytes.
Existing JPEG files can be compressed a bit more, with no additional loss in quality, using jpegtran -optimize. This results in a smaller file, but the compression is slower. Jpegtran is part of libjpeg. A package called littleutils contains a script called opt-jpg that automates JPEG optimization, using jpegtran as the underlying engine.