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The following code will rotate a Bitmap 90 degrees counter clockwise:
procedure TForm3.Rotate90(Bitmap:TBitmap);
type TRGBArray = array[0..0] of TRGBTriple;
pRGBArray = ^TRGBArray;
var oldRows,
oldColumns: integer;
rowIn,rowOut:
pRGBArray;
tmpBitmap: TBitmap;
begin
// Create tmp bitmap
tmpBitmap:=TBitmap.Create;
// Adjust tmp bitmap size and pixelformat (rotate 90 = W-> and H->W)
with tmpBitmap do
begin
tmpBitmap.Width:=Bitmap.Height;
tmpBitmap.Height:=Bitmap.Width;
tmpBitmap.PixelFormat:=Bitmap.PixelFormat;
end;
for oldColumns := 0 to Bitmap.Width - 1 do // oldColumns=newRows, oldRows=newColumns
begin
rowOut:=tmpBitmap.ScanLine[oldColumns];
// Fastest way is reading bit, so we work on one line in the new bitmap ata time
for oldRows:= 0 to Bitmap.Height - 1 do
begin
rowIn:=Bitmap.ScanLine[oldRows];
rowOut[oldRows]:=rowIn[Bitmap.Width - oldColumns -1];
end;
end;
// Copy bitmap to source and free tmp bitmap
bitmap.assign(tmpBitmap);
tmpBitmap.free;
end;
