[solved] Trouble with TLazCanvas.Arc

Forum > Graphics

(1/1)

Valdas:
Hello,

I' trying to adopt an example from the this post to produce an Arc.
Instead of

--- Code: Pascal [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---cnv.Ellipse(0, 0, BITMAP_SIZE, BITMAP_SIZE); I'm using

--- Code: Pascal [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---cnv.Arc(0, 0, 20, 20, 0, 180 * 16); But I'm not getting the Arc, only a green field.
Am I missing something?

wp:
Can you show your code so that I can reproduce it?

wp:
I see: TLazCanvas does not implement its Arc method, it inherites the one from TFpCustomCanvas, and this does - nothing...

Here is a quick-and-dirty procedure which you can call instead. It draws the arc as short line segments; their angular length is 5 degree - this is not optimized: for very small arcs you can increase the value because many points will be overlapping; and for large arcs you must decrease the value if you can distinguish the individual straight-line segments in the curve. (Ideally the procedure should be tuned to determine the correct value by itself).

--- Code: Pascal [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---uses Math;procedure Arc(ACanvas: TLazCanvas; ALeft, ATop, ARight, ABottom: Integer; AStartDeg, ASweepDeg: Double);var a, b: Double; phi, phi_end, dphi: Double; sinphi, cosphi: Double; x, y: Integer; Center: TPoint; done: Boolean = false;begin a := (ARight - ALeft) / 2; // major ellipse axis b := (ABottom - ATop) / 2; // minor ellipse axis Center := Point((ALeft + ARight) div 2, (ATop + ABottom) div 2); dphi := DegToRad(5); // 5-degree steps, not optimized if ASweepDeg < 0 then dphi := -dphi; phi := DegToRad(AStartDeg); phi_end := DegToRad(AStartDeg + ASweepDeg); sincos(phi, sinphi, cosphi); x := Center.X + round(cosphi * a); y := Center.Y - round(sinphi * b); ACanvas.MoveTo(x, y); repeat phi := phi + dphi; if ((ASweepDeg > 0) and (phi > phi_end)) or ((ASweepDeg < 0) and (phi < phi_end)) then begin phi := phi_end; done := true; end; sincos(phi, sinphi, cosphi); x := Center.X + round(cosphi * a); y := Center.Y - round(sinphi * b); ACanvas.LineTo(x, y); until done;end;
ALeft, ATop, ARight, ABottom define the rectangle enclosing the *full* ellipse from which the arc is cut. AStartDeg is the start angle of the arc, in degrees, measured from the x axis in counter-clockwise direction. ASweepDeg is the "length" of the arg given in degrees also. If positive the arc runs in counter-clockwise direction, otherwise in clockwise direction. The following sample draws a rounded rectangle:

--- Code: Pascal [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} --- Arc(cnv, 0, 0, 30, 30, 180, -90); cnv.Line(15, 0, img.Width-15, 0); Arc(cnv, img.Width-30, 0, img.Width-1, 30, 0, 90); cnv.Line(img.Width-1, 15, img.Width-1, img.Height-15); Arc(cnv, img.Width-30, img.Height-30, img.Width-1, img.Height-1, 0, -90); cnv.Line(img.Width-15, img.Height-1, 15, img.Height-1); Arc(cnv, 0, img.Height-30, 30, img.Height-1, -90, -90); cnv.Line(0, img.Height-15, 0, 15);

Valdas:
Thank you!

Navigation

[0] Message Index