Grenzen von PlgBlt

[Blup]

Hab mal schnell was geschrieben:

Delphi-Quellcode:

procedure Rotiere(ABitmap: TBitmap; ADirection: Integer);
{---}
const
  PIXELCOUNT = 8;
{---}
  function Rol(const AByte, APositions: Byte): Byte register; 
  asm
    mov cl, dl
    rol al, cl
  end;
{---}
  function Ror(const AByte, APositions: Byte): Byte register;
  asm
    mov cl, dl
    ror al, cl
  end;
{---}
  function CalcByteCount(AWidth: Integer): Integer;
  begin
    Result := AWidth div PIXELCOUNT;
    if (AWidth mod PIXELCOUNT) > 0 then
      Inc(Result);
  end;
{---}
var
  y, x1, x2, yMax, i, xCount, yCount: Integer;
  p1, p2, buffer: ^Byte;
  v, m: Byte;
begin
  {im Uhrzeigersinn drehen}
  if (ADirection = 90) or (ADirection = 180) or (ADirection = 270) then
  begin
    ABitmap.Pixelformat := pf1Bit;

    xCount := CalcByteCount(ABitmap.Width);
    yCount := CalcByteCount(ABitmap.Height);

    GetMem(buffer, xCount * yCount * PIXELCOUNT);
    try
      FillChar(buffer^, xCount * yCount * PIXELCOUNT, #0);

      yMax := ABitmap.Height - 1;

      if ADirection = 90 then
      begin
        m := 1 shl (PIXELCOUNT - 1);
        for y := yMax downto 0 do
        begin
          p1 := ABitmap.Scanline[y];
          p2 := buffer;
          Inc(p2, (yMax - y) div PIXELCOUNT);
          for x1 := 0 to xCount - 1 do
          begin
            v := p1^;
            for x2 := 0 to PIXELCOUNT - 1 do
            begin
              v := Rol(v, 1);
              if Odd(v) then
                p2^ := p2^ or m;
              Inc(p2, yCount);
            end;
            Inc(p1, 1);
          end;
          m := Ror(m, 1);
        end;
        ABitmap.SetSize(ABitmap.Height, ABitmap.Width);
        p2 := buffer;
      end
      else if ADirection = 270 then
      begin
        m := 1 shl (PIXELCOUNT - 1);
        for y := 0 to yMax do
        begin
          p1 := ABitmap.Scanline[y];
          Inc(P1, xCount - 1);
          p2 := buffer;
          Inc(p2, (y div PIXELCOUNT));
          for x1 := 0 to xCount - 1 do
          begin
            v := p1^;
            for x2 := 0 to PIXELCOUNT - 1 do
            begin
              if Odd(v) then
                p2^ := p2^ or m;
              v := Ror(v, 1);
              Inc(p2, yCount);
            end;
            Dec(p1, 1);
          end;
          m := Ror(m, 1);
        end;
        ABitmap.SetSize(ABitmap.Height, ABitmap.Width);
        p2 := buffer;
        {Leerzeilen überspringen}
        Inc(p2, yCount * ((xCount * PixelCount) - ABitmap.Height));
      end
      else if ADirection = 180 then
      begin
        p2 := buffer;
        i  := (ABitmap.Width mod PIXELCOUNT);
        for y := yMax downto 0 do
        begin
          p1 := ABitmap.Scanline[y];
          Inc(P1, xCount - 1);
          if i = 0 then
            v := 0
          else
          begin
            v := p1^;
            Dec(p1);
            v := Rol(v, i);
          end;
          for x1 := 0 to xCount - 1 do
          begin
            m := 0;
            for x2 := 0 to i - 1 do
            begin
              m := Rol(m, 1);
              if Odd(v) then
                m := m or 1;
              v := Ror(v, 1);
            end;
            if (i > 0) and (x1 = (xCount - 1)) then
              v := 0
            else
            begin
              v := p1^;
              Dec(P1);
            end;
            for x2 := i to PIXELCOUNT - 1 do
            begin
              m := Rol(m, 1);
              if Odd(v) then
                m := m or 1;
              v := Ror(v, 1);
            end;
            p2^ := m;
            Inc(p2);
          end;
        end;
        p2 := buffer;
      end
      else
        Exit;
      {Bitmap aus dem Buffer füllen}
      xCount := CalcByteCount(ABitmap.Width);
      for y := 0 to ABitmap.Height - 1 do
      begin
        p1 := ABitmap.Scanline[y];
        Move(p2^, p1^, xCount);
        Inc(p2, xCount);
      end;
    finally
      FreeMem(Buffer);
    end;
  end;
end;

Edit: Hoffe es ist einfach genug.