function FlattenQSpline(const pts: TArrayOfPointD): TArrayOfPointD;
This function converts QSpline points into a flattened path. It loosely approximates the 'T' command inside the 'd' property of an SVG path. In essence, a QSpline 'pts' array represents a series of points that define a series of joined quadratic bezier curves.
The first three coordinates of the spline represent the starting point, control point, and end point of the first sub-curve (just like a quadratic bezier curve). Subsequent points represent the end points for following sub-curves. Control points for following sub-curves are derived from the very first control point; with each new control point being the control point of the preceding sub-curve reflected across its end point.
uses Image32, Image32_PNG, Image32_Vector, Image32_Draw; ... var img: TImage32; path: TArrayOfPointD; pts: TArrayOfPointD; ghostPt: TPointD; begin img := TImage32.Create(256,256); //create and draw a BLUE QSpine path pts := MakePathI([10,70, 25,20, 40,70, 70,70, 100,70, 130,70, 160,70, 190,70, 220,70, 250,70]); path := FlattenQSpline(pts); DrawLine(img, path, 8, clBlue32, esRound); //show where the 'pts' are too for i := 0 to high(pts) do DrawPoint(img, pts[i], 3, clRed32); //and show the derived control points ghostPt := pts; for i := 2 to high(pts) do begin ghostPt := ReflectPoint(ghostPt, pts[i]); DrawPoint(img, ghostPt, 3, clSilver32); end; //CODE FOR (RED) CSPLINE OMITTED img.SaveToFile('splines.png'); img.Free; end;
In the image below the blue curve is a QSpine. The red dots indicate the user defined control and end points, and the pale gray dots indicate virtual control points (ie derived from preceding control points).
Copyright ©2019 Angus Johnson - Image32 ver. 1.37 - Documentation last updated on 15-January-2020