Method and apparatus for constructing, storing and displaying characters

Claim 1

A computer system for displaying characters on a video screen, comprising: storage means for storing a character as coefficients for spline curves which are a function of the character edges forming a boundary of the character; a look-up table including an index of stored pixelmap colors for each combination of character color, background color, and gray scale value; conversion means for converting said coefficients to form a pixelmap of the character, said pixelmap including gray scale values corresponding to said coefficients for spline curves from full on to full off for boundary pixels at the character edges and for selectively scaling the coefficients for displaying the character at different sizes; display means for displaying the pixelmap of the character in a selected color against a background having a different selected color; and means including the table of stored pixelmap colors for mixing the character color and the background color for each boundary pixel in accordance with the gray scale value of the boundary pixel, the mixing means including, means for extracting color bits representing component intensity from each of the red, blue and green components of each of the background and character colors, means for subtracting the background color component bits from the character color component bits to provide a difference color component value, means for combining the difference color component value with the gray scale of boundary pixels to provide the index for the look-up table, means for referencing a corresponding pixelmap color component in the look-up table using the index, and means for adding the corresponding background color component bits to the referenced pixelmap color component.

Claim 4

A method of operating a computer system for displaying a character on a video screen, comprising the steps of: storing a character as coefficients for spline curves which are a function of the character edges forming a boundary of the character; providing, in a look-up table having an index, pixelmap colors for each combination of character color, background color, and gray scale values; using said stored pixelmap colors for each boundary pixel; converting said coefficients to form a pixelmap of the character, said pixelmap including gray scale values from full on to full off for boundary pixels at the character edges and for selectively scaling said coefficients for displaying the character at different sizes; displaying the pixelmap of the character in a selected color against a background having a different selected color; and mixing the character color and the background color in the look-up table for each boundary pixel in accordance with the gray scale value of the boundary pixel, the step of mixing including, extracting color bits representing component intensity from each of the red, blue and green components of each of the background and character colors, subtracting the background color component bits from the character color component bits to provide a difference color component value, combining the difference color component value with the gray scale value of boundary pixels to provide an index for the look-up table, referencing a corresponding pixelmap color components in the look-up table using the index, and adding the corresponding background color component bits to the referenced pixelmap color components.

Claim 5

A method of operating a computer system for displaying a character on a video screen, comprising the steps of: storing a character as coefficients for spline curves which are a function of the character edges forming a boundary of the character; providing, in a look-up table having an index, pixelmap colors for each combination of character color, background color, and gray scale values; using said stored pixelmap colors for each boundary pixel; converting said coefficients to form a pixelmap of the character, said pixelmap including gray scale values from full on to full off for boundary pixels at the character edges and for selectively scaling said coefficients for displaying the character at different sizes; displaying the pixelmap of the character in a selected color against a background having a different selected color; and mixing the character color and the background color in the look-up table for each boundary pixel in accordance with the gray scale value of the boundary pixel, the step of mixing including, extracting color bits representing component intensity from each of the red, blue and green components of each of the background and character colors, subtracting the background color component bits from the character color component bits to provide a difference color component value, combining the difference color component value with the gray scale value of boundary pixels to provide an index for the look-up table, referencing a corresponding pixelmap color components in the look-up table using the index, and adding the corresponding background color component bits to the referenced pixelmap color components.

Claim 10

A method of operating a computer system for displaying characters on a video screen, comprising the steps of: storing in a look-up table pixelmap colors corresponding to each combination of character colors, background colors, and gray scale values from full on to full off for boundary pixels at the character edges; displaying the pixelmap of a respective character in a selected color against a background having a different color; and mixing the character color and the background color for each boundary pixel in accordance with the gray scale value of the boundary pixel; the step of mixing including, extracting color bits representing component intensity from each of the red, blue and green components of each of the background and character colors, subtracting the background color component bits from the character color component bits to provide a difference color component value, combining the difference color component value with the gray scale value of boundary pixels to provide an index for the look-up table, referencing a corresponding pixelmap color component in the look-up table using the index, and adding the corresponding background color component bits to the referenced pixelmap color components.

Claim 11

A method of operating a computer system for displaying characters on a video screen, comprising the steps of: storing in a look-up table pixelmap colors corresponding to each combination of character colors, background colors, and gray scale values from full on to full off for boundary pixels at the character edges; displaying the pixelmap of a respective character in a selected color against a background having a different color; and mixing the character color and the background color for each boundary pixel in accordance with the gray scale value of the boundary pixel; the step of mixing including, extracting color bits representing component intensity from each of the red, blue and green components of each of the background and character colors, subtracting the background color component bits from the character color component bits to provide a difference color component value, combining the difference color component value with the gray scale value of boundary pixels to provide an index for the look-up table, referencing a corresponding pixelmap color component in the look-up table using the index, and adding the corresponding background color component bits to the referenced pixelmap color components.

Claim 18

A method of operating a computer system for constructing and displaying characters at a plurality of different degrees of resolution comprising the steps of: setting up a higher resolution grid as an array of a plurality of pixels for display of characters at a higher resolution; setting up one or more lower resolution grids, each as an array of a lesser number of pixels, for display of characters at lower resolutions; constructing a character at the higher resolution by switching pixels on and off to fit the higher resolution grid; displaying the said character at the or each lower resolution; monitoring the shape of the said character as displayed at the or each lower resolution; altering the shape of the character at the higher resolution by changing pixels of the higher resolution grid in response to the monitored shape of the said displayed character at the or each lower resolution; repeatedly displaying, and monitoring the shape of, said character at the or each lower resolution and subsequently further altering the altered character until the character shape is visually acceptable when displayed at the higher and at each lower resolution; and generating spline curve coefficients for determining boundaries of said altered character at the higher resolution; storing said spline curve coefficients of the character at the higher resolution to provide a set of stored spline curve coefficients; scaling selectively said stored spline curve coefficients to obtain scaled coefficients for generating pixelmaps in accordance with said scaled coefficients; generating a pixelmap from the scaled coefficients, said pixelmap having gray scale values for each boundary pixel at the character edges corresponding to the percentage of the boundary pixel within the boundary as determined by said spline curve coefficients; and displaying a pixelmap for the character in accordance with the scaled coefficients.

Claim 19

A method of operating a computer system for constructing and displaying characters at a plurality of different degrees of resolution comprising the steps of: setting up a higher resolution grid as an array of a plurality of pixels for display of characters at a higher resolution; setting up one or more lower resolution grids, each as an array of a lesser number of pixels, for display of characters at lower resolutions; constructing a character at the higher resolution by switching pixels on and off to fit the higher resolution grid; displaying the said character at the or each lower resolution; monitoring the shape of the said character as displayed at the or each lower resolution; altering the shape of the character at the higher resolution by changing pixels of the higher resolution grid in response to the monitored shape of the said displayed character at the or each lower resolution; repeatedly displaying, and monitoring the shape of, said character at the or each lower resolution and subsequently further altering the altered character until the character shape is visually acceptable when displayed at the higher and at each lower resolution; and generating spline curve coefficients for determining boundaries of said altered character at the higher resolution; storing said spline curve coefficients of the character at the higher resolution to provide a set of stored spline curve coefficients; scaling selectively said stored spline curve coefficients to obtain scaled coefficients for generating pixelmaps in accordance with said scaled coefficients; generating a pixelmap from the scaled coefficients, said pixelmap having gray scale values for each boundary pixel at the character edges corresponding to the percentage of the boundary pixel within the boundary as determined by said spline curve coefficients; and displaying a pixelmap for the character in accordance with the scaled coefficients.