Effectuer une rotation de n'importe quel angle sur un Bitmap

const PixelMax = 32768;
type
pPixelArray = ^TPixelArray;
TPixelArray = Array[0..PixelMax-1] Of TRGBTriple;

procedure RotateBitmap_ads(
SourceBitmap : TBitmap;
out DestBitmap : TBitmap;
Center : TPoint;
Angle : Double) ;
var
cosRadians : Double;
inX : Integer;
inXOriginal : Integer;
inXPrime : Integer;
inXPrimeRotated : Integer;
inY : Integer;
inYOriginal : Integer;
inYPrime : Integer;
inYPrimeRotated : Integer;
OriginalRow : pPixelArray;
Radians : Double;
RotatedRow : pPixelArray;
sinRadians : Double;
begin
DestBitmap.Width:=SourceBitmap.Width;
DestBitmap.Height := SourceBitmap.Height;
DestBitmap.PixelFormat := pf24bit;
Radians := -(Angle) * PI / 180;
sinRadians := Sin(Radians) ;
cosRadians := Cos(Radians) ;
for inX := DestBitmap.Height-1 downto 0 do
Begin
RotatedRow := DestBitmap.Scanline[inX];
inXPrime := 2*(inX - Center.y) + 1;
for inY := DestBitmap.Width-1 downto 0 do
begin
inYPrime := 2*(inY - Center.x) + 1;
inYPrimeRotated := Round(inYPrime * CosRadians - inXPrime * sinRadians) ;
inXPrimeRotated := Round(inYPrime * sinRadians + inXPrime * cosRadians) ;
inYOriginal := (inYPrimeRotated - 1) div 2 + Center.x;
inXOriginal := (inXPrimeRotated - 1) div 2 + Center.y;
if
(inYOriginal >= 0) and
(inYOriginal <= SourceBitmap.Width-1) and
(inXOriginal >= 0) and
(inXOriginal <= SourceBitmap.Height-1)
then
begin
OriginalRow:=SourceBitmap.Scanline[inXOriginal];
RotatedRow[inY] := OriginalRow[inYOriginal]
end
else
begin
RotatedRow[inY].rgbtBlue:=255;
RotatedRow[inY].rgbtGreen := 0;
RotatedRow[inY].rgbtRed := 0
end;
end;
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
Center : TPoint;
Bitmap : TBitmap;
Angle: Double;
begin
Angle := StrToFloat(Edit1.Text);

Bitmap := TBitmap.Create;
try
Center.y := (Image1.Height div 2)+20;
Center.x := (Image1.Width div 2)+0;
RotateBitmap_ads(
Image1.Picture.Bitmap,
Bitmap,
Center,
Angle) ;
Angle := Angle + 15;
Image2.Picture.Bitmap.Assign(Bitmap) ;
finally
Bitmap.Free;
end;
end;

end.