Dot matrix characters are rounded by interpolating quarter dots in the angles of diagonal strokes with the feature that the video signal is a line interlaced signal; the diagonals are detected as predetermined logical combinations of an undelayed signal, a dot-delayed signal, a line delayed signal and a line-plus-dot delayed signal; the quarter dots are interpolated in real time as the diagonals are detected but are interpolated in a first one of the said signals in first fields and in a second one of the said signals in the second, interlaced fields, the second signal being line-delayed relative to the first signal.
A line interlaced video signal having odd and even alternating fields produces an alphanumeric character display in the form of a dot matrix character, each matrix location comprising segments of two next adjacent lines in the display. To improve the resolution of the characters, diagonals are detected and partly filled to provide a rounded effect. Two parallel-in serial-out shift registers are used, one of the shift registers having an associated input buffer store. A binary word representing dot information for one row of a character is read out from a dot matrix character generator ROM and loaded into one of the shift registers. On even (odd) fields the ROM output for the previous (succeeding) row is read and loaded into the other shift register. The last two bits of the two shift registers are compared to detect diagonals in the character information and used to modify the video signal to lengthen the leading or trailing edge of the corresponding dot to produce the rounded character.
A system for expanding a dot-matrix for characters being displayed on a television raster scan display to improve the readability and resolution of displayed characters without a corresponding increase in the size of the Read-Only Memory (ROM) employed to generate the pattern of dots defining the characters. This result is accomplished by first displaying the identical dot-matrix stored in the ROM for each character in each row of characters to be displayed on the first pass of the raster scan. On the second pass of the raster scan, which is interlaced between the lines of the first pass of the raster scan, a new dot-matrix is inserted according to a predetermined logical real time comparison of the dot matrix of the adjacent rows of the dots produced during the first raster scan.
A 2-level quantized video signal, composed of background level and character-pattern delineating level time intervals in which transitions between levels only occur at an end of one or more elemental timing periods, is modified to a 3-level quantized video-signal in which the difference between the character-pattern delineating and background levels is increased for at least one of the first and last entire elemental timing periods of the duration of each occurring character-pattern delineating level interval.
A special slanted line pattern is detected using pattern data of eight picture elements S0-S3, S5-S8 which surround a current display picture element S4. A half-picture element pattern provided on the current display picture element S4 and having a specified positional relationship to the detected pattern is added to this detected pattern, is deleted from the detected pattern, or is added to the detected pattern and given the same color as the detected pattern.
A desired character mainly composed of standard width dots selected from a matrix of orthogonally disposed rows and columns is displayed on a screen during scanning of the screen in horizontal and vertical directions. The display is smoothed by a circuit responsive to data stored in a memory. The smoothing involves the selected addition or removal, to or from particular portions of the character, of a small dot having a width one-third of the standard dot width.
