Virtual resolution displays

• US 4,720,705 A
• Filed: 09/13/1985
• Issued: 01/19/1988
• Est. Priority Date: 09/13/1985
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Lucas, Bruce D., Gupta, Satish
• Primary Examiner(s): Brigance, Gerald L.
• Assistant Examiner(s): Brier, Jeffery A.
• Application Number:
  US06/775,570
• Time in Patent Office: 858 Days
• Field of Search: 340/730, 340/724, 340/728, 340/731, 340/735, 340/744, 340/748, 340/790, 382/45, 382/47
• US Class Current: 345/20
• CPC Class Codes: G09G 1/002 Intensity circuits G09G1/06 - G09G1/28 take precedence
• CPC Class Codes: G09G 5/28 for enhancement of character form, e.g. smoothing

Abstract

A method for improving the viewing quality of a CRT display image without increasing resolution of the display. With the invention disclosed herein, characters are apparently positioned at sub-pixel locations to improve the viewing quality of a CRT display image. This apparent positioning is accomplished by changing intensity values assigned to pixels on a CRT display. In the preferred embodiment, the change in intensity values is effected by linear interpolation with intensity values of neighboring pixels to yield second intensity values. These second intensity values, then, improve the viewing quality of the CRT display image.

Claims

1. A method for improving the viewing quality of a CRT display image by apparently positioning a number of characters appearing therein at sub-pixel locations, which said number of characters are formed from a plurality of pixels and are actually positionable only at pixel locations, said number of characters being apparently positioned at sub-pixel locations by means of command signals containing sub-pixel address locations, which signals represent commands to position said number of characters at sub-pixel locations in the CRT display field in which the image is formed, the address locations being from file formats and corresponding to pixel locations in a given display field which has a higher resolution than the CRT display field in which the image appears, said method comprising the steps of:

(a) assigning respective intensity values to pixels, so that each pixel has, at any given time, only one intensity value, and so that, the intensity value of any given pixel of the CRT display, is proportional to the sum of weighted averages of bi-level intensity values of corresponding pixels of the given display field, the corresponding pixels being pixels which form a first area of the given display field corresponding to a second area on the CRT display, which second area contains the given pixel of the CRT display field, the bi-level intensity values of the pixels of the first area of the given display field being converted into a single multilevel intensity value to be assigned to the given pixel of the second area; and

(b) changing certain of the intensity values obtained in step (a), of the pixels forming the number of characters, to corresponding second intensity values by linear interpolation, the intensity value, assigned to CRT pixel whose intensity value is to be changed, being changed by linear interpolation, with an unchanged intensity value assigned to a pixel adjacent to the pixel whose intensity value is to be changed, each pixel still having only one intensity value assigned thereto, whereby the number of characters appear to be positioned at sub-pixel locations to improve the viewing quality of the CRT display image.

2. A method for improving viewing quality of a CRT display image by apparently positioning a number of characters of the image at sub-pixel locations in the CRT display field in which the image appears, which said number of characters are formed from a plurality of pixels and are actually positioned only at CRT pixel locations, said number of characters being apparently positioned at sub-pixel locations by means of command signals containing sub-pixel address locations, which signals represent commands to position said number of characters at sub-pixel locations, each pixel having at most one intensity value assigned thereto, the sub-pixel address locations being from file formats and identifying pixel locations in a given display field which has a higher resolution than the CRT display field, said method comprising the steps of:

(a) storing in a CRT display memory for the CRT display field at most one respective low resolution representation for each character of a font which provides characters for an image in the given display field;

(b) assigning first intensity values to CRT pixels of the CRT display field to correspond to the low resolution representations stored in step (a), the first intensity values also being assigned as if the number of characters were to be actually and apparently positioned at CRT pixel locations; and

(c) changing first intensity values, obtained in step (b) of certain of the pixels forming the number of characters to corresponding second intensity values by linear interpolation, a first intensity value (of the first intensity values), assigned to a CRT pixel whose first intensity value is to be changed, being changed by linear interpolation, with a first intensity value assigned to a pixel adjacent to the pixel whose first intensity value is to be changed, each pixel still having only one intensity value assigned thereto, whereby a number of the characters appear to be positioned at sub-pixel locations to improve the viewing quality of the CRT display image.

3. A method as recited in claim 2, wherein the linear interpolation comprises at most one linear interpolation for each CRT pixel forming the number of characters, the interpolation being only with intensity values assigned to two adjacent pixels in the same row or between one intensity value assigned to a pixel in the row and an intensity value assigned to a pixel horizontally adjacent to the row.

4. A method for improving the viewing quality of a CRT display image by apparently positioning characters appearing therein at sub-pixel locations, which characters are formed from a plurality of pixels and which are actually positionable only at pixel locations in a CRT display field, the characters being apparently positioned at sub-pixel locations by means of command signals containing sub-pixel address locations and first pixel intensity values, which signals represent commands to position the characters at sub-pixel locations, each pixel, at any given time, having assigned thereto a single first intensity value selectable from permissible values in a predefined range, said method comprising the step of changing the first pixel intensity values of certain of the pixels forming the characters to be apparently positioned at sub-pixel locations (but actually positioned at pixel locations) to second intensity values also selectable from the permissible values in the predefined range, the changing of the first intensity values being made by linear interpolation using pairs of first intensity values assigned to adjacent pixels of the CRT display, whereby the characters, actually positioned at pixel locations, appear to be positioned at sub-pixel locations to improve the viewing quality of the CRT display image.

5. A method for improving the viewing quality of a CRT display image, as recited in claim 4, wherein the sub-pixel address locations are from file formats which contain pixel address locations in a display field of higher resolution than that of the CRT display in which the image appears.

6. A method, for improving the viewing quality of a CRT display image as recited in claim 4, wherein intensity values, before being changed, are assigned to respective pixels in the CRT display, in which the image appears, so that the intensity value, of any given CRT pixel, is proportional to the sum of weighted averages of bi-level intensity values of corresponding pixels of the given display field, the corresponding pixels being pixels which form a first area corresponding to a second area on the CRT display, which second area contains the given pixel.