아래의 소스는 일반 Unit에서는 잘 동작을 합니다.
이걸 DLL로 만드니 에러가 발생하는데
메시지는 invalid pointer operation 입니다.
군데군데 메시지를 출력해보니
if lbl_Str.Canvas.Pixels[(iStep*8)+j-1,i-1] = clBlack then begin
부분에서 에러가 발생하는 것 같은데
Unit에서는 잘되는것이 왜 에러가 생기는지 알 수 가 없네요....

Function MakeHangul(sHanStr,sFontName:string; iX, iY, iSize, iType : integer) : String;
var
    iWidth, iHeight : integer;
    i,j,w,a,iStep,iPos : integer;
    sData,Str: string;
    Form1 : TForm;
    lbl_Str : TLabel;
begin
    Form1 := TForm.Create(Application);
    lbl_Str := TLabel.Create(Form1);

    if sHanStr = '' then exit;
    lbl_Str.Font.Name := sFontName;
    lbl_Str.Font.Size := iSize;
    lbl_Str.Font.Color := clBlack;

    if iType = 1 then
        lbl_Str.Font.Style := [fsBold]
    else
        lbl_Str.Font.Style := [];


    iWidth  := lbl_Str.Width;
    iHeight := lbl_Str.Height;

    iStep := 0;
    iPos :=  0;

    while iWidth > 0 do
    begin
        if (iWidth - 8) > 0 then  begin
            w := 8;
            iWidth := iWidth - 8;
        end else begin
            w := iWidth;
            iWidth := 0;
        end;

        sData := '';

        for i := 1 to iHeight do begin
            a := $00;
            for j := 1 to w do begin
                if lbl_Str.Canvas.Pixels[(iStep*8)+j-1,i-1] = clBlack then begin
                    case j of
                      1 : a := a OR $80;
                      2 : a := a OR $40;
                      3 : a := a OR $20;
                      4 : a := a OR $10;
                      5 : a := a OR $08;
                      6 : a := a OR $04;
                      7 : a := a OR $02;
                      8 : a := a OR $01;
                    end;
                end;
            end;
            sData := sData + IntToHex(a,2);
        end;

        Str := str + '~DGimg'+IntToStr(iImgCount)+','+IntToStr(iHeight)+',1,'+sData;
        Str := str + '^FO'+IntToStr(iPos+iX)+','+IntToStr(iY);
        Str := str + '^XGimg'+IntToStr(iImgCount)+',1,1^FS';
        inc(iStep);
        iPos := iPos + 8;
        inc(iImgCount);
    end;
    Result := str;
    Form1.Free;
    lbl_str.Free;
end;

Exports
   MakeHangul;