Rotate Bitmap at any angle, any center of rotation

Submitted by:David Villa

Date added:04 April, 2012

Category:Delphi

Delphi code example to rotate a TBitmap at any angle

Tags: rotate bitmap

Code Snippet:

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;

{Usage:}
procedure TForm1.Button1Click(Sender: TObject) ;
Var
Center : TPoint;
Bitmap : TBitmap;
begin
Bitmap := TBitmap.Create;
Try
Center.y := (Image.Height div 2)+20;
Center.x := (Image.Width div 2)+0;
RotateBitmap_ads(
Image.Picture.Bitmap,
Bitmap,
Center,
Angle) ;
Angle := Angle + 15;
Image2.Picture.Bitmap.Assign(Bitmap) ;
Finally
Bitmap.Free;
End;
end;
 
 

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