How to "flush" changes to a bitmap's ScanLine - delphi

Question

I'm currently trying to add mirroring to our RotateBitmap routine (from http://www.efg2.com/Lab/ImageProcessing/RotateScanline.htm). This currently looks like this (BitMapRotated is a TBitmap) in pseudo-code:
var
RowRotatedQ: pRGBquadArray; //4 bytes
if must reflect then
begin
for each j do
begin
RowRotatedQ := BitmapRotated.Scanline[j];
manipulate RowRotatedQ
end;
end;
if must rotate then
begin
BitmapRotated.SetSize(NewWidth, NewHeight); //resize it for rotation
...
end;
This works if I either must rotate or reflect. If I do both then apparently the call to SetSize invalidates my previous changes via ScanLine. How can I "flush" or save my changes? I tried calling BitmapRotated.Handle, BitmapRotated.Dormant and setting BitmapRotated.Canvas.Pixels[0, 0] but without luck.
Edit: I found the real issue - I'm overwriting my changes with values from the original bitmap. Sorry for the effort.

Answer 1

Perhaps this is not really an answer, but this code works in both D2006 and XE3 and gives the expected result. There is no need to 'flush' anything.
procedure RotateBitmap(const BitMapRotated: TBitmap);
type
PRGBQuadArray = ^TRGBQuadArray;
TRGBQuadArray = array [Byte] of TRGBQuad;
var
RowRotatedQ: PRGBQuadArray;
t: TRGBQuad;
ix, iy: Integer;
begin
//first step
for iy := 0 to BitMapRotated.Height - 1 do begin
RowRotatedQ := BitMapRotated.Scanline[iy];
// make vertical mirror
for ix := 0 to BitMapRotated.Width div 2 - 1 do begin
t := RowRotatedQ[ix];
RowRotatedQ[ix] := RowRotatedQ[BitMapRotated.Width - ix - 1];
RowRotatedQ[BitMapRotated.Width - ix - 1] := t;
end;
end;
//second step
BitMapRotated.SetSize(BitMapRotated.Width + 50, BitMapRotated.Height + 50);
//some coloring instead of rotation
for iy := 0 to BitMapRotated.Height div 10 do begin
RowRotatedQ := BitMapRotated.Scanline[iy];
for ix := 0 to BitMapRotated.Width - 1 do
RowRotatedQ[ix].rgbRed := 0;
end;
end;
var
a, b: TBitmap;
begin
a := TBitmap.Create;
a.PixelFormat := pf32bit;
a.SetSize(100, 100);
a.Canvas.Brush.Color := clRed;
a.Canvas.FillRect(Rect(0, 0, 50, 50));
b := TBitmap.Create;
b.Assign(a);
RotateBitmap(b);
Canvas.Draw(0, 0, a);
Canvas.Draw(110, 0, b);