JPEG Image File Format

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JPEG

Joint Photographic Experts Group is one of the most popular file formats for storing 8 and 24 bit continuous tone grayscale and color images (which makes it one of the more popular web graphic formats. It is a standardized image compression mechanism designed for compressing either full-color or gray-scale images. It works well on photographs, artwork, and similar material. However, it does not work as well on lettering, simple cartoons, or line drawings. JPEG works by exploiting known limitations of the human eye, notably the fact that small color changes are perceived less accurately than small changes in brightness.

JPEG is lossy but it achieves much greater compression than is possible with lossless methods. A major disadvantage of lossy compression is that repeated compression and decompress will continue to deteriorate image quality. The amount of "loss" can be varied by adjusting compression parameters that determine image quality and speed of decoding. This means that image size is offset by image quality or the amount of time needed to decode the image file for display. JPEG does not support transparency.

The highly efficient JPEG compression modes are:

  • Non-differential Huffman coding
  • Differential Huffman coding
  • Non-differential arithmetic coding
  • Differential arithmetic coding
PDF TIFF JPEG EMF
GIF PCX DCX BMP
IBM IOCA IBM MODCA CALS TGA
CCITT FAX PNG DICOM