function hIconToFile(FileName: String; hIcon1: Cardinal; 
                     iconBitCount: TBitCount): Integer;

function autoIconToFile(FileName: String; hIcon1: Cardinal): Integer;

  TMutiIcon = Record
    hIcon: Cardinal;
    BitCount: TBitCount;
    end;

function IconsToStream(Stream: TStream; aryMutiIcon: Array of TMutiIcon;
                       NumIcons: Byte = 1): Integer;

function TestMultiIcons(aryMutiIcon: Array of TMutiIcon; 
                         NumIcons: Byte): Cardinal;

function Icon32To24File(FileName: String; hIcon: Cardinal): Integer;

The Get48hIcon function looks like this -

function Get48hIcon(FileName: String; icoIndex: Integer = 0): Integer;

Get48hIcon function Result - The Result of this Get48hIcon function is an Integer value, which will be a system Icon Handle if the function is successful. If the function Fails, the Result is Zero. You should ALWAYS test for failure (result is equal to zero) of this function.

If there is at least ONE Icon bitmap of any size in the file, this function will get a system generated 48x48 icon handle, even if the file does NOT have a 48x48 icon bitmap in it.

procedure TForm1.autoIconToFileClick(Sender: TObject);
begin
if autoIconToFile('E:\aTest Icon.ico', Application.Icon.Handle) < 0 then
ShowMessage('ERROR - autoIconToFile was NOT able to Write the Icon to disk file');
end;

procedure TForm1.Icon2FileClick(Sender: TObject);
var
ShInfo1: TSHFILEINFO;
hIcon1: Cardinal;
Return: Integer;
ReStr: String;
begin
Return := hIconToFile('E:\aTest1.ico', Application.Icon.Handle, BitC24);
if Return < 0 then
  begin
  if Return = -1 then
    ReStr := 'ERROR - File name has less than 4 charaters'
  else
  if Return = -2 then
    ReStr := 'ERROR - hIcon is NOT a valid handle for an Icon'
  else
  if Return = -3 then
    ReStr := 'ERROR - could not get Icon''s Bitmap stuctures from the operating system'
  else
  if Return = -4 then
    ReStr := 'ERROR - Icon''s Bitmap pixel definition are Invalid'
  else
  if Return = -5 then
    ReStr := 'ERROR - Could not retrive system Bitmap Data'
  else
  if Return = -6 then
    ReStr := 'ERROR - Could not Create a file with the Path and file name'
  else
  if Return = -7 then
    ReStr := 'ERROR - Could not Write to disk, disk space unavailable or disk IO error'
  else
    ReStr := 'ERROR - Undetermined Error';
  ShowMessage(ReStr);
  end else
  ShowMessage(IntToStr(Return));

{the next two hIconToFile show how to get and use system HICON with
the hIconToFile function}
SHGetFileInfo('C:\Windows\NotePad.exe', 0, ShInfo1, SizeOf(TSHFILEINFO),
             SHGFI_ICON);
ShowMessage(IntToStr(hIconToFile('E:\New1.ico', ShInfo1.hIcon, BitC24)));

if OpenPicDlg1.Execute then
  if UpperCase(ExtractFileExt(OpenPicDlg1.Filename)) = '.ICO' then
    begin
    hIcon1 := ExtractIcon(hInstance, PChar(OpenPicDlg1.Filename), 0);
    if hIcon1 > 0 then
    ShowMessage(IntToStr(hIconToFile('E:\Icon 8bit.ico', hIcon1, BitC8)));
    end;
end;

procedure TMainForm1.sbut_MultiIconClick(Sender: TObject);
var
aryMulIco: Array[0..0] of TMutiIcon;
Return: Integer;
FileStream1: TFileStream;
begin
aryMulIco[0].hIcon := Application.Icon.Handle;
AryMulIco[0].BitCount := BitC4;
FileStream1 := TFileStream.Create('E:\Multi Icon.ico', 
                                  fmCreate or fmOpenWrite or fmShareDenyWrite);
try
  Return := IconsToStream(FileStream1, aryMulIco);
  finally
  FileStream1.Free;
  end;
ShowMessage('The Result of IconsToStream is '+IntToStr(Return));
end;

procedure TMainForm1.sbut_MultiIconClick(Sender: TObject);
var
aryMulIco: Array[0..3] of TMutiIcon;
ShInfo1: TSHFILEINFO;
Return: Integer;
MemStream1: TMemoryStream;
begin
aryMulIco[0].hIcon := Application.Icon.Handle;
aryMulIco[0].BitCount := BitC4;

SHGetFileInfo(PChar(ParamStr(0)), 0, ShInfo1, SizeOf(TSHFILEINFO),
             SHGFI_ICON or SHGFI_SMALLICON);
{the SHGetFileInfo fuction with the SHGFI_SMALLICON flag set will get
the handle of the Small Icon, 16x16}
aryMulIco[1].hIcon := ShInfo1.hIcon;
aryMulIco[1].BitCount := BitC4;

aryMulIco[2].hIcon := Application.Icon.Handle;
aryMulIco[2].BitCount := BitC8;

aryMulIco[3].hIcon := ShInfo1.hIcon;
aryMulIco[3].BitCount := BitC8;
Return := 123;
MemStream1 := TMemoryStream.Create;
try
  MemStream1.Write(Return, SizeOf(Integer));
  Return := IconsToStream(MemStream1, aryMulIco, 4);
  ShowMessage('MemStream size '+IntToStr(MemStream1.Size)+' Return '+IntToStr(Return));
  finally
  MemStream1.Free;
  end;
end;

procedure TMainForm1.sbut_Icon32to24Click(Sender: TObject);
var
ShInfo1: TSHFILEINFO;
begin
SHGetFileInfo('C:\Program Files\Internet Explorer\IExplore.exe', 0, 
               ShInfo1, SizeOf(TSHFILEINFO), SHGFI_ICON);
ShowMessage(IntToStr(Icon32To24File('E:\Icon 32 to 24.ico', ShInfo1.hIcon)));
end;

procedure TMainForm1.sbut_Icon2File2Click(Sender: TObject);
var
hIcon1: Cardinal;
AryMulIco: Array[0..9] of TMutiIcon;
ShInfo1: TSHFILEINFO;
Return: Cardinal;
Str1: String;
begin
hIcon1 := Application.Icon.Handle;
AryMulIco[0].hIcon := hIcon1;
AryMulIco[0].BitCount := BitC8;
AryMulIco[2].hIcon := hIcon1;
//AryMulIco[2].BitCount := BitC4;
AryMulIco[2].BitCount := BitC8;
AryMulIco[4].hIcon := hIcon1;
AryMulIco[4].BitCount := BitC1;
AryMulIco[6].hIcon := hIcon1;
AryMulIco[6].BitCount := BitC24;
//AryMulIco[6].BitCount := BitC8;
SHGetFileInfo(PChar(ParamStr(0)), 0, ShInfo1, SizeOf(TSHFILEINFO),
             SHGFI_ICON or SHGFI_SMALLICON);
AryMulIco[1].hIcon := ShInfo1.hIcon;
//AryMulIco[1].hIcon := hIcon1;
AryMulIco[1].BitCount := BitC8;
AryMulIco[3].hIcon := ShInfo1.hIcon;
//AryMulIco[3].hIcon := 22;
AryMulIco[3].BitCount := BitC4;
AryMulIco[5].hIcon := ShInfo1.hIcon;
AryMulIco[5].BitCount := BitC1;
AryMulIco[7].hIcon := ShInfo1.hIcon;
AryMulIco[7].BitCount := BitC4;
//AryMulIco[7].BitCount := BitC24;
Return := TestMultiIcons(AryMulIco, 8);
if Return > 100000 then
  begin
  if Return < 900000000 then
    Str1 := 'ERROR - Undetermined Error'
  else
  if Return = 900000000 then
    Str1 := 'ERROR - the NumIcons is zero or above 15'
  else
  if Return = 900000001 then
    Str1 := 'ERROR - the NumIcons is higher than the number of elements in the MutiIcon Array'
  else
  if Return < 1000000100 then
    Str1 := 'ERROR - the Icon index '+IntToStr(Return - 1000000000)+
                                    ', hIcon is NOT an ICON Handle'
  else
  if Return < 1000000200 then
    Str1 := 'ERROR - the Icon index '+IntToStr(Return - 1000000100)+
                                     ', is a Two Color Icon without a bits Bitmap structure'
  else
  if Return < 1000000300 then
    Str1 := 'ERROR - the Icon index '+IntToStr(Return - 1000000200)+
                     ', the hIcon Bitmap will not get system Object information from GetObject( )'
  else
  if Return <  2000000100 then
  Str1 := 'ERROR - the Width and Height of Icon is Incorrect for a standard Icon, for icon index '+
              IntToStr(Return - 2000000000)
  else
  Str1 :='ERROR - Undetermined Error';
  end else // Return > 100000
if Return <> 0 then
begin
{you can use the test for a bit in the Result with a
if Return and 2 <> 0 then
The first bit will never be set, since there are no Icons before it}
Str1 := 'Duplicate Icon Indexes are ';
if Return and 2 <> 0 then
Str1 := Str1+'1, ';
if Return or 4 = Return then
Str1 := Str1+'2, ';
if Return or 8 = Return then
Str1 := Str1+'3, ';
if Return or 16 = Return then
Str1 := Str1+'4, ';
if Return or 32 = Return then
Str1 := Str1+'5, ';
if Return or 64 = Return then
Str1 := Str1+'6, ';
if Return or 128 = Return then
Str1 := Str1+'7, ';
if Return or 256 = Return then
Str1 := Str1+'8, ';
if Return or 512 = Return then
Str1 := Str1+'9, ';
if Return or 1024 = Return then
Str1 := Str1+'10, ';
if Return or 2048 = Return then
Str1 := Str1+'11, ';
if Return or 4096 = Return then
Str1 := Str1+'12, ';
if Return or 8192 = Return then
Str1 := Str1+'13, ';
if Return or 16384 = Return then
Str1 := Str1+'14, ';
if Return or 32768 = Return then
Str1 := Str1+'15';
end else
Str1 := 'All Icons are GOOD';
ShowMessage(Str1+' | '+IntToStr(Return));
end;

procedure TMainForm1.sbut_Get48hIconClick(Sender: TObject);
var
Filename: String;
hIcon48: Integer;
begin
FileName := 'C:\Icons\My Icon.ico';
hIcon48 := Get48hIcon(FileName);
if hIcon48 <> 0 then
    DrawIconEx(Canvas.Handle,60,48, hIcon48, 0, 0, 0, 0, DI_NORMAL) else
      ShowMessage('FAILURE - Get48hIcon');
DestroyIcon(hIcon48);
end;

procedure TMainForm1.sbut_Get48hIconClick(Sender: TObject);
var
Filename: String;
hIcon48: Integer;
begin
FileName := 'C:\Windows\Notepad.exe';
hIcon48 := Get48hIcon(FileName, 1);
if hIcon48 <> 0 then
    DrawIconEx(Canvas.Handle,60,48, hIcon48, 0, 0, 0, 0, DI_NORMAL) else
      ShowMessage('FAILURE - Get48hIcon');
DestroyIcon(hIcon48);
end;