Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Reexamination Certificate
1995-12-07
2001-06-19
Liang, Regina (Department: 2674)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
C345S182000
Reexamination Certificate
active
06249273
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of displaying characters with a border on a display device as a raster consisting of raster lines and raster columns, the character information being derived from a memory, as well as to a device for displaying characters with a border on a raster consisting of raster lines and raster columns, and comprising a data source for supplying the character information.
A method of this kind is known from U.S. Pat. No. 5,003,303. Therein, the character information for each raster point of the character contains a multidigit value. This value is transformed into a part of the overall value range, and in parallel therewith an expanded form of the character element is formed in the other part of the value range, for example in that for each raster field it is tested whether a character element is present within a matrix field of given size around the relevant raster field. After rotation or shifting of the character, if applicable, the two value ranges are separately backtransformed into the overall value range again, and a selectable colour is assigned to the border information. Finally, the overall character information with border is stored in an image memory wherefrom display takes place.
The image memory is necessary because the many processing steps required for each individual raster point of the character to be displayed cannot be executed at the display speed. Such an image memory, however, represents a substantial expenditure.
In order to save such a character memory, the image information of the characters to be displayed, for example letters or digits character-wise stored in a character memory and addressed by character codes, is read often in synchronism with the display on the display device, i.e. in synchronism with the deflection of the electron beam in the case of a picture tube. The characters are customarily reproduced in a selectable colour on a background which is also selectable. The background may also be transparent, for example when the characters are to be superposed on a television image in given positions. In case the colour of the image part on which the characters are to be superposed happens to be the same as the colour selected for the characters and the background of the characters is transparent, the characters displayed cannot be recognized.
One possibility of making the characters recognizable still on a background of arbitrary colour consists in providing the characters with a border on at least some sides; such a border is also referred to as a shade. This border is reproduced in a different colour, so that either the characters or the border can always be reliably recognized, regardless of the colour of the background. For other reasons, for example so as to achieve a more aesthetic display, it may also be desirable to display characters with a border. This border may be desired at one or two sides, for example at the top and at the right, so that it appears as a shade; however, it may also be desirable to provide a border at three or at all four sides.
Therefore, it is an object of the invention to provide a method of the kind set forth which enables the display of arbitrary characters with a minimum expenditure, notably without using an image memory, and with a border at arbitrarily selectable sides.
SUMMARY OF THE INVENTION
This object is achieved in accordance with the invention in that, in order to generate the border (shade) at selectable sides of the character, in synchronism with the raster points displayed a line signal is formed such that, for each raster line to be displayed, the character information of the relevant raster line is combined column by column with the character information of a first number of preceding and/or succeeding raster lines of the character in conformity with the sides selected for the border. Such line signal is column-wise delayed by up to twice a second number of columns. The first number denotes the height of the border in raster lines, and the second number denotes the width of the border in raster columns. There is also formed a character signal in which raster line information concerning the character to be displayed is delayed by said second number of columns. Finally, a shade signal is formed from the combination of differently delayed line signals in conformity with the sides selected for the border, the character signal then being suppressed from this combination and the shade signal generating a selectable colour at corresponding raster points of the raster line displayed.
Thus, the basic idea of the invention is to store only the basic shape of the characters and to add the border on-line during display; thus, in the case of periodic display such as on a picture tube the border is also generated periodically. First the information for an upper or lower edge is then generated, and therefrom the additional information for a left-hand or right-hand edge is formed. For the sake of simplicity, the border information is formed also for the raster point associated with the information of the basic character to be displayed, after which it is suppressed again by this character information. This results in a method which can be readily implemented to achieve selectable bordering of characters and which can also be used when the character information is pixel-wise stored, for example for an image part of a complete image.
It is often desired to display selectable characters with a different size, for example double the height, double the width or twice the overall size. For a better image presentation such characters are then displayed with a border which is wider than that of characters of normal size. Therefore, a version of the method in accordance with the invention is characterized in that, for the purpose of selection of different border widths, the first number corresponds to the selected border width and the second number corresponds to the maximum border width, and the delayed line signals are combined in conformity with the selected border width and the selected side for the border in order to form the shade signal. The border width is thus also variable within a line of characters or also within a raster line.
It is to be noted that for a border the number of lines for the upper or the lower edge may differ from the number of raster points for the side edges, i.e. the first and the second number are different.
A display device of comparatively simple construction suitable for carrying out the method in accordance with the invention by controlling the display of characters on a raster consisting of raster lines and raster columns, and comprising a data source for supplying the character information in synchronism with the raster points displayed, in accordance with the invention is characterized in that the following elements are provided for the display of characters with a border (shade) at selectable sides of the characters:
a) a control device which reads from the data source, for each raster line of a character to be displayed, also the information of a first number of preceding and/or succeeding raster lines of the character corresponding to the border width, in conformity with the sides selected for the border,
b) a combinatory device which combines the information of corresponding columns of the individually read raster lines of the character so as to form a line signal,
c) a first delay device which delays the information of the instantaneous raster line to be displayed by a second number of columns which corresponds to the border width and outputs it as a character signal,
d) a second delay device which delays the line signal by up to double the second number of columns and outputs it column-wise,
e) a combination device which combines the column-wise delayed line signals in conformity with the sides selected for the border,
f) a suppression device which suppresses the combined, delayed line signals upon occurrence of a character signal and which applies the non-suppressed signal as a shade signal to the display device in order
Liang Regina
Thorne Gregory L.
U.S. Philips Corp.
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