Technique for scaling characters in a stroke-vector display system

Abstract

A technique is disclosed for use in an electronic raster-scan display system, for generating characters of variable size using a stroke-vector technique. An incoming data signal defines the type of character to be displayed, the horizontal X and vertical Y character field dimensions, the character drawing point, and any character rotation or reflection. Using that part of the data signal that defines the character type as a memory address, a character microprogram is retrieved containing a stroke-vector character mask and a stroke resolution factor representing the number x of horizontal stroke-vectors in a straight line and the number y of vertical stroke-vectors in a straight line that are used by said character mask to represent said character within a normalized character field. To scale the size of the stroke-vectors the horizontal length stroke-vector attribute DX-LENGTH is forming by taking the quotient X/x, and the vertical length stroke-vector attribute DY-LENGTH is forming by taking the quotient Y/y. Then the DX-LENGTH attribute and the DY-LENGTH attribute are converted from the display screen coordinate system to a virtual screen coordinate system having a greater resolution than the physical screen coordinate system. One or both length attributes can be applied to each stroke-vector. At this point the character image having the proper size exists in the virtual screen coordinate system. To convert it back to the actual display screen coordinate system the size attributes DX-LENGTH and DY-LENGTH are divided down by the proper factor. Lastly a logical pel may be generated and added to the individual stroke-vectors before the connected stroke-vectors are projected onto the display screen at the character drawing point.