In a circuit for rotating a digital image any multiple of ninety degrees, an addressing method which reduces the number of address lines required. The rotation circuit relies on a memory configuation which can access each image pixel in memory individually, and this normally requires a large number of address lines. This invention takes advantage of the periodic nature of the data being accessed to reduce the number of address lines required.

A graphic display system includes a set of rendering engines and a plurality of data storage units. Each data storage unit in the set of data storage units is coupled to at least one rendering engine in the set of rendering engines. A selection means is included in the graphic display system for selecting a data storage unit in the plurality of data storage units. The selected data storage unit is to be used for storing data representing an object to be displayed by the graphic display system and is selected based on a validity period of the object. The selection means includes means for determining a size validity period of the object and means for determining a translational validity period of the object. The translational validity period is a time required for the object to change by a predetermined translational threshold, wherein the predetermined translational threshold is a first angle extending from a line that passes through both a reference point and the object. The size validity period is a time required for the object to change by a predetermined size threshold, wherein the predetermined size threshold is a second angle extending from the line.

A graphics drum plotter in which wide strip paper is divided into virtual columns. An operator interface is provided whereby an operator can define the size and number of columns across the strip paper. Instead of producing a series of small plots along one edge of the wide strip, the system includes logic to place the series of plots sequentially across the columns of the strip paper before advancing the strip paper to a next writing area. A paper slitter is also provided to slit the paper on the column lines after the printing thereon.

An image processing apparatus especially suitable for image processing operations such as enlarging, reducing, rotating and scrolling avoids use of a second video memory. The image processing device comprises a memory having memory elements for storing picture element data of a video information which describes an original image, an operation circuit for receiving a start address where a read operation is to start within the memory and a predetermined data indicative of a difference between the start address and a next address where the read operation is to be made, and for calculating the next address from the start address data and the predetermined data, a reading circuit for reading the picture element data which is stored in the memory at the next address calculated by the operation circuit, and an output circuit for outputting the picture element data read by the reading circuit. The picture element data output from the output circuit describe at least a portion of the original image subjected to a predetermined image processing operation.

A method and apparatus for entering data in a random access memory with a fixed orientation independent of the heading vector of the carrier vehicle. The data remains positionally fixed in the memory and is addressed for readout in a manner to present a heading-up display for all vehicle heading vectors.