Bitmaps: Rotate Bitmap any angle (slow)

// Make sure to add Math to your uses clause.

[code lang=”delphi”]procedure TForm1.bmp_rotate(src,dst:tbitmap;angle:extended);
var
c1x,c1y,c2x,c2y:integer;
p1x,p1y,p2x,p2y:integer;
radius,n:integer;
alpha:extended;
c0,c1,c2,c3:tcolor;
begin
//calculate the angle to pi-format
angle := (angle / 180) * pi;

// calculate the central points
c1x := src.width div 2;
c1y := src.height div 2;
c2x := dst.width div 2;
c2y := dst.height div 2;

// number of steps
if c2x < c2y then n := c2y else n := c2x; dec (n,1); // starting rotation for p2x := 0 to n do begin for p2y := 0 to n do begin if p2x = 0 then alpha:= pi/2 else alpha := arctan2(p2y,p2x); radius := round(sqrt((p2x*p2x)+(p2y*p2y))); p1x := round(radius * cos(angle+alpha)); p1y := round(radius * sin(angle+alpha)); c0 := src.canvas.pixels[c1x+p1x,c1y+p1y]; c1 := src.canvas.pixels[c1x-p1x,c1y-p1y]; c2 := src.canvas.pixels[c1x+p1y,c1y-p1x]; c3 := src.canvas.pixels[c1x-p1y,c1y+p1x]; dst.canvas.pixels[c2x+p2x,c2y+p2y]:=c0; dst.canvas.pixels[c2x-p2x,c2y-p2y]:=c1; dst.canvas.pixels[c2x+p2y,c2y-p2x]:=c2; dst.canvas.pixels[c2x-p2y,c2y+p2x]:=c3; end; application.processmessages end; end; // Here is how to call it procedure TForm1.bmpRotateClick(Sender: TObject); Var RAngle : Extended; begin RAngle := StrToFloat(Edit1.Text); bmp_rotate(Image1.Picture.Bitmap,Image2.Picture.Bitmap, RAngle); end; [/code] [tags]Delphi, Graphic[/tags]