Method and apparatus for displaying a high resolution image on a low resolution CRT

• US 4,924,522 A
• Filed: 05/11/1989
• Issued: 05/08/1990
• Est. Priority Date: 08/26/1987
• Status: Expired due to Term

• Current Assignee: NCR Corporation (NCR Voyix Corporation)
• Original Assignee: NCR Corporation (NCR Voyix Corporation)
• Inventors: Poos, David, Bray, John E.
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Couso, Jose L.
• Application Number:
  US07/351,264
• Time in Patent Office: 362 Days
• Field of Search: 340/703, 340/723, 340/729, 340/730, 340/731, 340/750, 340/793, 340/814, 358/263, 358/287, 358/21 R, 358/433, 358/451, 364/521, 382/47, 382/50-53, 382/56
• US Class Current: 382/237
• CPC Class Codes: G06T 3/4023 based on decimating pixels or lines of pixels; based on inserting pixels or lines of pixels
• CPC Class Codes: H04N 5/00 Details of television systems scanning details or combination thereof with generation of supply voltages H04N3/00

Abstract

A method and apparatus for displaying a high resolution image on a low resolution CRT with a minimal loss of information. Even rows of a source or matrix of binary pixels are stored in an "even" video RAM and odd rows are stored in an "odd" video RAM at addresses corresponding to the locations of the binary pixels within the matrix. In a preferred embodiment, a group of four pixels corresponding to a portion of the image is converted to a single gray value which is used to control the intensity of the beam control within the CRT.

Claims

1. In a system in which image data for an image is provided in the form of a matrix of binary pixels of a first predetermined resolution, the method of displaying said image data onto a CRT having a resolution lower than said first predetermined resolution, comprising the steps:

(a) selecting a block of four of said pixels which represents a predetermined area of said image data;

(b) examining only the status of each pixel in said predetermined area to determine whether it is a binary one or a binary zero;

(c) assigning a predetermined value ranging from zero through three for the various combinations of binary ones and binary zeros which exist in said block of four pixels in said predetermined area, with said predetermined value representing said block of four pixels;

(d) using a said predetermined value to control a gray scale value ranging from completely white to completely black for displaying on said CRT said gray scale value as representing solely said predetermined area of said image, said displaying being effected on said CRT at a resolution which is lower than said first predetermined resolution;

(e) selecting in a predetermined order or examining pattern an adjacent and completely new block of four pixels which represents said predetermined area for said image; and

(f) repeating steps b, c, and d for said adjacent predetermined area and the remaining predetermined areas for the entire said image until the entire image is completely displayed.

2. The method as derived in claim 1 in which said selecting step e is effected by moving along rows of said matrix of binary pixels until the last column of pixels in said matrix is selected.

3. A system comprising:

a source of image data of a first predetermined resolution stored in the form of a matrix of rows and columns of binary pixels;

first means for storing even rows of said binary pixels in a first memory at addresses corresponding to their locations in said matrix;

second means for storing odd rows of said binary pixels in a second memory at addresses corresponding to their locations in said matrix;

means for selecting from said first and second means a group of four of said pixels corresponding to a predetermined area of said matrix of binary pixels;

representing means for representing said group of four binary pixels as a single gray scale value which is a function of the number of binary pixels of a first type within said group of four binary pixels corresponding to a predetermined area of said matrix of binary pixels, said gray scale value ranging from zero through three; and

display means for displaying said single gray scale value at a location corresponding to said predetermined area of said matrix of binary pixels;

said display means including a beam control and a CRT having a resolution which is less than said first predetermined resolution, with said gray scale value being used to control the intensity of said beam control.

4. The system as claimed in claim 3 in which said first and second means include first and second video memories, respectively.

5. The system as claimed in claim 3 in which said representing means includes a look-up table whose output is said gray scale value.

6. The system as claimed in claim 4 in which said first and second video memories include ports which are coupled to said look-up table to provide addresses thereto for determining a said gray scale value.