Method for dynamically viewing image elements stored in a random access memory array

A method of generating a graphics display comprised of n rows and m columns of discrete picture elements, comprising:

• storing a set of picture element data in a memory device having storage sites corresponding to an N.times.M array;
• selecting a particular portion of the storage sites corresponding to an m/Z.times.n/Z array where n/Z is equal to or less than N and m/Z is equal to or less than M;
• reading out in raster fashion the data contained in each row of said portion and supplying said data as a raster signal, the data in each storage site being supplied Z times, where Z is an integer, and the data read out of each row being repeated Z times before data from the next row is read out;
• using said raster signal in a video display device to produce a "zoomed" display of the data contained in said portion, said display containing a Z.times.Z array of picture elements corresponding to each storage site in said portion of said N.times.M array, and
• selectively inhibiting the supply of data from each storage site for one or more of the Z consecutive supply times, and inhibiting the corresponding ones of the repeat readouts of each row of data such that a zoomed display of a plurality of adjacent storage sites containing data will be displayed as an array of spaced apart dots rather than as a solid area.

A method of generating a graphics display having a background grid comprising:

• storing a set of data in a memory device, said stored data respectively representing the displayable picture elements of an image;
• sequentially reading out in raster fashion the data contained in said memory device to develop a raster data signal;
• simultaneously generating a grid signal including a train of pulses which occur in a series of regularly timed intervals;
• mixing said raster data signal and said grid signal to develop a composite raster display signal in which read out datum components of said raster data signal are combined with simultaneously occurring pulses of said grid signal, said composite raster display signal being utilizable by a raster-type video display device to produce a graphics display including the data read out of said memory device and a background grid including vertical and horizontal grid lines of data superimposed on the displayed picture element data.

In a computer graphics display apparatus for producing in raster fashion a display image having n rows and m columns of discrete image elements, a zoom system comprising:

• a memory having storage sites each capable of storing data representing a discrete image element;
• memory control means for storing in separate, non-intersecting subarrays of said memory, each subarray having at least n.times.m storage sites, data representing the same picture at different scales;
• raster display generation means for reading out in raster fashion data from a block of n.times.m sites in a selected one of said subarrays and for generating therefrom a display image of at least a portion of the stored picture;
• and
• zoom magnification control means, cooperating with said generation means, for selecting from which one of said subarrays said data is read out, selection of different subarrays thereby resulting in display images of the same picture at different effective "magnification" scales.

In a computer graphics display in which a display is generated from an image stored in a memory:

• first means for storing a first set of data in said memory in alternate locations;
• second means for storing a second set of data in locations intermediate said alternate locations, said second set of data representing a second image that is positionally overlapping the image represented by said first set of data;
• and
• means for accessing said memory containing both first and second sets of said data and for generating a display therefrom, creating a display thereby including said first and second images in overlapping positions but with non-intersecting image elements.

A process for implementing smooth panning in a computer graphics display system of the type having a memory storing digital data corresponding to picture elements of an image that is larger than can be displayed at one time, and in which a subset of said stored digital data is read out from said memory and supplied to a video display device in raster fashion to produce on said device a display of the portion of said image represented by said data subset, each such data subset being specified by a corresponding origin address within said memory, comprising:

• generating a pan clock signal that is synchronized with the frame rate of said video display device,
• providing a first origin address specifying a first data subset representing that first position of said image at which panning is to begin,
• selecting a second origin address specifying a second data subset representing the second portion of said image at which panning is to terminate,
• establishing a group of intermediate origin addresses specifying data subsets representing closely, sequentially contiguous portions of said image intermediate said first and second portions, and
• sequentially reading out said first, said group of intermediate and said second data subsets in raster fashion for supply to said video display device to produce corresponding sequential displays of the portions of said image represented thereby, each such sequential readout being synchronized with said pan clock signal, whereby the resultant display has the illusion of smooth panning in which each successive video frame synchronized display represents a portion of said image that is closely contiguous to the preceeding display.