Mega Code Archive
Bitmap Rotation
<![CDATA[
Title: Bitmap Rotation
Question: I've been searching for a good and fast BitmapRotation function for some time now, and finally I found a function that did this really fast.
Unfortunatelly the source was written in some Delphi and some Assembler. The Assembler was quite easy to exchange with the Move() command, but I also needed it to rotate around the center of the bitmap.
After some changes I came up with this solution. It's actually pretty fast for being a Delphi only function, but not as fast as the original one.
The BackgroundColor parameter of RotateDraw24 specifies the background color to replace for smoothing the rotation a little bit.
Another idea might be to check if the NewColor = SrcBitmap.TransparentColor to make the rotation better for transparent rotation.
I don't know who the original author was since the zip file I downloaded didn't say anything about that. Credits go out to him!
Answer:
Unit Rotation;
Interface
Uses windows, Graphics;
Procedure RotateDraw24(Angle: Real; BackgroundColor: TColor; SrcBitmap, DstBitmap: tbitmap);
Implementation
Uses SysUtils;
Type
BScan = Array of PByteArray;//Pointer;
Function ScanBitmap(Bit1: TBitmap) : BScan;
Var
Y : Integer;
Begin
SetLength(result,bit1.height);
For Y := Bit1.Height-1 downto 0 do Result[Y] := Bit1.ScanLine[Y];
End;
Procedure RotateDraw24(Angle: Real; BackgroundColor: TColor; SrcBitmap, DstBitmap: tbitmap);
var
OnS,FrS : BScan;
cosr,sinr : Real;
x, y : Integer;
x2, y2 : Integer;
NewColor : Integer;
CurColor : Integer;
BackColor : Integer;
DstPos : Integer;
scx, scy : Integer; // Source
dcx, dcy : Integer; // Destination
Begin
Angle := Angle * pi / 180;
scx := (SrcBitmap.Width div 2);
scy := (SrcBitmap.Height div 2);
dcx := (DstBitmap.Width div 2);
dcy := (DstBitmap.Height div 2);
// Convert the RGB value specified by BackgroundColor to BGR used by the BMP format.
BackColor := Rgb(GetBValue(BackgroundColor), GetGValue(BackgroundColor), GetRValue(BackgroundColor));
// if the bitmaps are not in pf32bit, this may take a
// little while to convert the pixel formats
DstBitmap.pixelformat := pf24bit;
SrcBitmap.pixelformat := pf24bit;
OnS := ScanBitmap(DstBitmap);
FrS := ScanBitmap(SrcBitmap);
// get the sin and cos values in fixed format
cosr := Cos(Angle);
sinr := Sin(Angle);
For x:=SrcBitmap.Width-1 downto 0 do
Begin
For y := SrcBitmap.Height-1 downto 0 do
Begin
x2 := dcx + Round( (scx-x) * cosr - (scy-y) * sinr );
y2 := dcy + Round( (scx-x) * sinr + (scy-y) * cosr );
// x2 and y2 are now the coordinates of the destination pixel
IF x2 -1 Then
Begin
IF x2 Begin
IF y2 -1 Then
Begin
IF y2 Begin
// If x2,y2 is actually inside the rectangle of
// the destination bitmap then ...
Move(FrS[Y]^[x*3], NewColor, 3);
DstPos := x2*3;
Move(NewColor, OnS[y2]^[DstPos], 3);
IF (x2 0) Then
Begin
// If smoothing isn't wanted, remove the IF sentence below...
Move(OnS[y2]^[DstPos-3], CurColor, 3);
IF (CurColor = BackColor) Then Move(NewColor, OnS[y2]^[DstPos-3], 3);
End;
IF (x2 Begin
// If smoothing isn't wanted, remove the IF sentence below...
Move(OnS[y2]^[DstPos+3], CurColor, 3);
IF (CurColor = BackColor) Then Move(NewColor, OnS[y2]^[DstPos+3], 3);
End;
End;
End;
End;
End;
End;
End;
End;
End.
// ------------------------- END OF UNIT -------------------------
Var
SrcBitmap : TBitmap;
DstBitmap : TBitmap;
Begin
SrcBitmap := TBitmap.Create;
SrcBitmap.LoadFromFile('Coffee Bean.bmp');
DstBitmap := TBitmap.Create;
DstBitmap.Width := 200;
DstBitmap.Height := 200;
DstBitmap.Canvas.Brush.Color := clRed;
DstBitmap.Canvas.FillRect( Rect(0, 0, DstBitmap.Width, DstBitmap.Height) );
RotateDraw24(45, DstBitmap.Canvas.Brush.Color, SrcBitmap, DstBitmap);
Canvas.Draw(0, 0, DstBitmap);
DstBitmap.Free;
SrcBitmap.Free;
End;
]]>