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.