1. A display data compression method in which a plurality of display data representing dots displayed on a screen of a display are divided into a plurality of two-dimensional blocks, which are subjected to reversible compression, said display data compression method comprising the steps of:
performing scanning on the display data of each block in accordance with a first scanning method, by which the display data are rearranged and are then subjected to compression using a Huffman table;
repeatedly performing scanning on the display data of each block in accordance with a second scanning method, by which the display data are rearranged and are then subjected to compression using a Huffman table; and
selecting the scanning method for realizing a smallest number of effective bits in compressed data, thus selectively outputting the compressed data based on the selected scanning method.
2. A display data compression method according to claim 1, wherein the compression is realized by performing differential operation on adjacent data included in the rearranged display data, thus producing differential data.
3. A display data compression device in which a plurality of display data representing dots displayed on a screen of a display are divided into a plurality of two-dimensional blocks, which are subjected to reversible compression, said display data compression device comprising:
a first means for performing scanning on the display data of each block in accordance with a prescribed scanning method, which is selected from among a plurality of scanning methods, thus rearranging the display data;
a second means for performing compression on the rearranged display data using a Huffman table, thus producing compressed data; and
a third means for selectively outputting the compressed data having a smallest number of effective bits, which are produced in accordance with the selected scanning method.
4. A display data compression device according to claim 3, wherein the compression is realized by performing differential operation on adjacent data included in the rearranged display data, thus producing differential data.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A device of single-piece, molded plastic construction for releasably holding an optical disc having two disc sides, an outer circular-shaped disc rim and a central disc opening and for substantially covering one of said disc sides while leaving the other of said disc sides uncovered, said device comprising a double-sided, plate-like cover and disc retainer structure projecting outwardly from one side of said cover for entering the central disc opening of an optical disc and frictionally engage said optical disc to provide a releasable connection between said optical disc and said device, said cover having cover segment portions with outer peripheral edges extending along spaced portions of the outer disc rim of said optical disc when said optical disc is releasably connected to said cover, and said cover defining spaced, inwardly extending notches between said cover segment portions exposing spaced areas of said optical disc extending inwardly from said outer disc rim to allow manual engagement of said rim when separating the device and the optical disc, and flange segments of substantially uniform height and thickness extending outwardly from the outer peripheral edges of said cover segment portions in the direction said disc retainer structure projects outwardly from said cover, said flange segments partially surrounding and spaced from said movable disc retainer structure, said flange segments terminating at said notches and extending along separate spaced arcs of a circle larger than said outer circular-shaped disc rim whereby said flange segments are immediately adjacent to but spaced from the outer circular-shaped disc rim when the optical disc is releasably connected to said cover, said flange segments extending outwardly a distance slightly greater than the thickness of said optical disc, the outer periphery of said device being rounded at the locations of said flange segments, and said flange segments being free of outwardly extending projections or other structure to facilitate the placement of said device and any optical disc held thereby into a retention sleeve, said disc retainer structure including at least one flexible retention member manually engageable by a user simultaneously with manual engagement of the outer disc rim by the user at the location of said two notches to simultaneously apply with a single hand a pushing force on said at least one flexible member and a force on the outer circular-shaped disc rim at both of said locations opposed to said pushing force to cause separation of the device from the optical disc while retaining the optical disc in hand.
2. The device according to claim 1 wherein two of said notches are disposed along an imaginary straight line bisecting said cover.
3. The device according to claim 2 wherein said two notches disposed along said imaginary straight line bisecting said cover are located on opposite sides of and spaced from said disc retainer structure, said disc retainer structure also disposed along the said imaginary straight line bisecting said cover.
4. The device according to claim 1 wherein said cover is transparent whereby the disc side covered by the cover can be observed from a location externally of said cover.