Abstract:
A system for localizing a region of a display incorporates a plurality of resettable counters for defining the position and extent of a cursor in two dimensions. Data is set into the counters periodically at the beginning of each frame, or at the beginning of each scanning line, so that the size and shape of the cursor is selectable, as well as its position on the display. When the data is modified during successive time periods, the cursor can be made to progressively reduce its size so as to indicate a point, and/or to progressively change its location.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a system for the localization of regions in a mixed text-picture display and more particularly to such displays in which information is displayed with two brightness levels. 
     2. The Prior Art 
     In connection with the processing of display patterns having mixed text and picture elements, an operator must have aids available which make possible a localization of both the text elements, and elements of the picture. In a case of text processing, such an aid is generally known as a cursor, which is usually in the form of a rectangle. 
     It is also necessary to have a means for determining the placement of picture elements which do not cover the entire display surface, such as handwriting, sketches and the like. 
     The term &#34;cursor&#34; refers to a temporary marking on a display screen which emphasizes to a user, in an optical manner, a momentarily important location on the picture. In the case of data display devices, it is for example a dash or a brighter appearance of the character or line which is to be processed next. Such apparatus is described in &#34;Elektronik&#34;, 1978, Pamphlet 4, Index Card Number 399. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The principal object of the present invention is to provide a novel shape of a cursor by which localization of individual points on the display screen is made possible. 
     Another object of the present invention is to provide a cursor which is easily recognizable independently of the information presented in the display. 
     A further object of the present invention is to provide a system for localizing regions in a mixed text-picture display where the display screen presents the information with two brightness levels. 
     In accordance with one embodiment of the present invention, the region to be localized is defined by means of a cursor having a rectangular shape serving as the background for information which remains visible as either brighter or darker than normally presented information. The size of the rectangular cursor is controllable so that the cursor assumes the size of the rectangular surface to be located or the size of the character to be located. For the location of a point, the cursor pulsates, along with a step-by-step reduction of its surface area, moving toward the point to be located. 
     The present invention has the advantage that the cursor is suitable for the location of random regions on the display, including character of text or points, with picture surfaces which are to be localized being brightened or darkened in such a manner that the picture information remains visible. 
     These and other objects or advantages of the present invention will become manifest by an examination of the following description and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference will now be made to the accompanying drawings in which: 
     FIG. 1 is a schematic illustration of the rectangular cursor having a size corresponding to the surface of the display which is to be localized; 
     FIG. 2 is a schematic illustration of the cursor with an area corresponding to a text character to be localized; 
     FIG. 3 is a schematic diagram showing the principle by which the cursor pulsates, along with a step-by-step reduction of its size, moving toward a point which is to be located; and 
     FIG. 4 is a functional block diagram of an exemplary circuit arrangement for realizing the cursor of the present invention. 
     FIG. 5 is a timing diagram for the exemplary circuit arrangement. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The cursor of the present invention is illustrated in diagrammatic form in FIG. 1, where the cursor is illustrated as a shaded rectangle. The size and shape of the rectangle may be controlled so as to designate a particular localized area of the display. 
     In the case of a character being localized, the cursor assumes the form of a square surrounding the character, with the character being visible with the cursor serving as the background for the character. In FIG. 3, the cursor is illustrated at five successive moments, which illustrate the manner in which the cursor reduces its size in order to indicate a point, shown as the fourth time position of FIG. 3. In the fifth time position, the cursor resumes a large size, after which the reduction in size, during successive time intervals, is repeated. The cursor may pulse on and off, as it changes size, in order to be more noticeable to an operator. 
     In FIG. 4, a schematic diagram of apparatus for generating the cursor is illustrated. Four presettable digital counters Z 0  through Z 3  are incorporated, and each of the counters is periodically preset by signals Set 0-3. The counters Z 0  and Z 1  are preset at the beginning of each frame of the display caused by signal VSYNC and determine respectively the position and length of the cursor rectangle, measured in a direction perpendicular to the scanning line. The counters Z 2  and Z 3  are set at the beginning of each scan line caused by signal HSYNC and determine respectively the position and length of the cursor rectangle in the direction along the scan line. The counters are preset at the proper times according to FIG. 5 by means of logic 24 and a data bus 10 illustrated in shaded form and which is labeled &#34;PRESET DATA, SET 0-3&#34; in FIG. 4. The counter Z 0  is thereafter counted down by sync pulses on line 12, occurring at the beginning of each scanning line, and when the counter Z 0  reaches zero, it produces an output signal which sets the flip-flop FF 1 . Thereafter, sync pulses are supplied to the counter Z 1  through an AND-gate 14 and when the counter Z 1  is counted down to zero, the flip-flop FF 1  is reset. Accordingly, the Q output of the flip-flop FF 1  is high only during the period that the display screen is being scanned with lines passing through the rectangular cursor area. 
     The counter Z 2  is counted down with pulses from a pulse generator which are supplied to a line 16, there being a predetermined number of such pulses per line. When the counter Z 2  reaches zero, a flip-flop FF 2  is set, after which the counter Z 3  is counted down by pulses supplied through an AND-gate 18. When the counter Z 3  is counted to zero, the flip-flop FF 2  is reset. Accordingly, the Q output of the flip-flop FF 2  is high only during the period of each scanning line corresponding to the position of the cursor rectangle relative to its scanning lines. 
     An AND-gate 20 receives as inputs the Q outputs of both flip-flops, and the signal is supplied to a video mixer unit D/A which mixes the signal with a signal representative of picture information originating from the unit B. The output of the video mixer is applied to the video monitor M, so that the picture information and the rectangular cursor are additively displayed on the monitor. 
     It is apparent that the position of the cursor is dependent on the quantities preset into the counters Z 0  and Z 2 , and that the vertical and horizontal dimensions of the cursor are determined by the quantities preset into the counters Z 1  and Z 3 . The quantities can all be determined independently, so as to select any desired size and shape of the rectangle, and to position it anywhere in the display area. Its position and/or size can be varied during successive frames of the display, by changing the quantities which are preset into the counters Z 0  -Z 3  to achieve the desired effect. These quantities are stored in registers X-position, X-size, Y-position, and Y-size, controlled by computer output and a motor control unit 22, e.g. a joy stick. For example, the decreasing size of the cursor as shown in FIG. 3, is achieved by decreasing the quantity preset into the counters Z 1  and Z 3  during successive time periods. In order to achieve pulsing, one or both of the counters Z 0  and Z 2  is set to its maximum count during periods in which no cursor display is desired. Such settings are alternated with settings which correspond to the desired position of the pulsing cursor. In addition, the cursor can be illustrated as moving by periodically changing the quantities preset into the counters Z 0  and Z 2 , depending on whether a vertical or horizontal movement, or both, is desired. 
     It will be appreciated that the output level of the signal from the AND-gate 20 is selected to give the cursor a brightness level different from that of the characters of text which are to be located, so that the text characters are not obliterated and obscured. 
     Although in the above, the cursor is illustrated as being rectangular, it will be apparent that a different form of cursor may be generated such as a triangle or an arrow, for example, by changing the quantities which are preset into the counters Z 2  and Z 3  as required, at the beginning of each scan line of the display image. 
     In operation, the operator may define the size and position of the rectangular cursor by first using the point mode, and moving the point-indicating cursor to the point corresponding to the upper left-hand corner of the desired rectangular cursor. This movement may be carried out in the well-known manner, using a joy stick or other movement controls 22. This movement is effected by presetting counters Z 0  and Z 2  with progressively larger or smaller quantities, in dependence on the desired direction of movement left and right, and up and down, under control of the joy stick. When the point cursor reaches the position desired for the upper left-hand corner of the rectangular cursor, the operator operates a control (not shown) which fixes the quantities preset into the counters Z 0  and Z 2 . Thereafter, the joy stick controls the presetting of the counter Z 1  and Z 2 , with progressively larger (or smaller) quantities, in response to movement of the joy stick in the known manner, which establishes the size and shape of the rectangular cursor. The quantities derived in this way, for presetting the counters, may be stored for later use by a program control, which causes the cursor to appear at the selected location and with the selected size, when required. 
     Although the present invention has been described in the foregoing in terms of a display screen which employs a scanning mechanism for scanning plural parallel lines in succession, it will be apparent that the present invention may be employed in any display system. Various other modifications and additions may be made to the present invention without departing from the essential features of novelty thereof, which are intended to be defined and secured in the appended claims.