Method and apparatus for generating a character curve by dividing and developing a bezier curve

• US 5,309,521 A
• Filed: 06/19/1991
• Issued: 05/03/1994
• Est. Priority Date: 06/28/1990
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Jukogyo Kabushiki Kaisha (Mitsubishi Heavy Industries, Ltd.)
• Original Assignee: Mitsubishi Jukogyo Kabushiki Kaisha (Mitsubishi Heavy Industries, Ltd.)
• Inventors: Matsukawa, Tadahiro
• Primary Examiner(s): COUSO, YON JUNG
• Application Number:
  US07/717,819
• Time in Patent Office: 1,049 Days
• Field of Search: 382/47, 382/22, 382/23, 382/24, 382/25, 395/142, 395/141, 395/143, 340/728
• US Class Current: 345/469
• CPC Class Codes: G06T 11/203 Drawing of straight lines or curves

Abstract

A control computer, an error calculator, a Bezier curve divider and an output device are provided for generating a character curve. Coordinates of end points and control points of a Bezier curve are input to the control computer. The error calculator determines squares of distances of the input control points from a straight line connecting the end points as errors. If these errors exceed a tolerable range, the curve divider divides the curve into two parts, and new coordinates of new end points and control points of a divided Bezier curve are input to the error calculator. The curve division and error calculation are repeatedly carried out until the calculated errors fall within the tolerable range. The end points of the respective divided curves are connected by straight lines to develop the original curve.

Claims

1. An image processing method for a raster image processor in which character data indicative of display coordinates of a character curve is generated based on input data indicative of coordinates of a preset Bezier curve, said method comprising:

a first step of inputting the input data indicative of the coordinates of the preset Bezier curve into a control computer of the raster image processor, the coordinates of the input data including first and second end points of the preset Bezier curve and first and second control points defining the Bezier curve which are intermediate the first and second end points;

a second step of applying the input data from the control computer to an error calculator circuit which is configured to generate error data denoting respective distances from said first control point and said second control point to a straight line connecting said first and second end points of the preset Bezier curve;

a third step of inputting the error data generating by said error calculator circuit to said control computer and determining whether the respective distances from said first control point and said second control point to said straight line connecting said first and second end points of the preset Bezier curve fall within a preset tolerable range;

a fourth step of applying character data denoting the straight line connecting said first and second end points of the present Bezier curve from the control computer to an output display device when the respective distances denoted by the error data fall within the tolerable range;

a fifth step of applying the input data from the control computer to a curve divider circuit when the respective distances denoted by the error data fall outside the tolerable range, the curve divider circuit configured to generate divided curve data denoting coordinates of a first curve segment forming a Bezier curve having as end points said first end point and a common dividing point and having two intermediate control points defining the first curve segment and a second curve segment forming a Bezier curve having as end points said common dividing point and said second end point and having two intermediate control points defining the second curve segment;

a sixth step of repeatedly carrying out in succession said second through fifth steps with respect to each curve segment denoted by the divided curve data generated by said curve divider circuit until the respective distances denoted by error data corresponding to each curve segment fall within the tolerable range.

2. An image processing apparatus comprising:

a raster image processor in which character data indicative of display coordinates of a character curve is generated based on input data indicative of coordinates of a preset Bezier curve, the coordinates of the input data including first and second end points of the preset Bezier curve and first and second control points defining the Bezier curve which are intermediate the first and second end points; and

,

an output device, coupled to said raster image processor, for receiving the character data generated by said raster image processor;

said raster image processor comprising,

(a) a first dedicated circuit having plural inputs for receiving respective input data denoting coordinates of a first input curve defined by two end points and two control points intermediate the two end points and having a hardware configuration which generates error data denoting respective distances from said two control points to a straight line connecting said two end points of the first input curve,

(b) a second dedicated circuit having plural inputs for receiving respective input data denoting coordinates of a second input curve defined by two end points and two control points intermediate the two end points and having a hardware configuration which generates divided curve data denoting coordinates of a first curve segment forming a Bezier curve having as end points one of said two end points of said second input curve and a common dividing point and having intermediate two control points defining the first curve segment and a second curve segment forming a Bezier curve having as end points said common dividing point and the other of said two end points and having two intermediate control points defining the second curve segment, and,

(c) a control computer means, coupled to the output device and to the first and second dedicated circuits, for effecting a first processing of receiving the input data indicative of the coordinates of the preset Bezier curve, a second processing of applying the input data as the first input curve to the first dedicated circuit to obtain error data from said first dedicated circuit with respect to said preset Bezier curve, a third processing of determining based on the error data whether the respective distances from said first control point and said second control point to a straight line connecting said first and second end points of the preset Bezier curve fall within a preset tolerable range, a fourth processing of applying character data denoting the straight line to the output device when the respective distances denoted by the error data fall within the tolerable range, a fifth processing of applying the input data as the second input curve to the second dedicated circuit when the respective distances denoted by the error data fall outside the tolerable range to obtain divided curve data denoting coordinates of a first curve segment forming a Bezier curve having as end points said first end point and a common dividing point and having two intermediate control points defining the first curve segment and a second curve segment forming a Bezier curve having as end points said common dividing point and said second end point and having two intermediate control points defining the second curve segment, and a sixth processing of repeatedly carrying out in succession said second through fifth processings with respect to each curve segment denoted by the divided curve data generated by said second dedicated circuit until the respective distances denoted by error data corresponding to each curve segment fall within the tolerable range.

3. An image processing apparatus as recited in claim 2, wherein the output device includes at least one of a display monitor, a printer and a memory.