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| Jacket | The paper cover sometimes called the "dust cover" of a hardbound book |
| Jaggies | As observed along a diagonal line of square pixels. Especially apparent in low resolution graphical images |
| JFIF | JFIF also known as the JPEG File Interchange Format is the technical name for the file format more widely known as JPEG |
| Job Offset | Job Offset is where each printed document in the printer's output tray is offset to either the left or right of the previous printed document allowing each document to be easily identified |
| Jog | To vibrate a stack of finished pages so that they are tightly aligned for final trimming |
| JPEG (Joint Photographics Experts Group) | Named after the Joint Photographic Experts Group who devised it. The JPEG format compresses images but sacrifices image detail (lossy compression) |
| JPEG2000 (JP2) | A file format which uses wavelet based image compression which offers high compression ratios without the image degradation associated with standard JPEG compression |