Function GetDocsCount(Dir: String; count: integer): integer;
Var
 SearchRec: TSearchRec;
begin
//добавляем все найденные файлы в таблицу
 try
   if Dir <> '' then Dir := IncludeTrailingPathDelimiter(Dir);
   if FindFirst(Dir + '*.*', faAnyFile, SearchRec) = 0 then
     repeat
       if (SearchRec.name='.') or
          (SearchRec.name='..') or
          (AnsiUpperCase(SearchRec.name) = AnsiUpperCase(sThumbnailFileName)) or
          (SearchRec.Name = '') then continue;
       if ((SearchRec.Attr and faDirectory) <> 0) then
         count := GetDocsCount(Dir + SearchRec.name, count) //we found Directory: "Dir+SearchRec.name"
       else
         begin
           Inc(count);
           
         end;

     until FindNext(SearchRec) <> 0;

 finally
   FindClose(SearchRec);
 end;
 result := count;
end;

Function GetDocsCount(Dir: String): integer;
begin
  result := Length(TDirectory.GetFiles(dir, '.', TSearchOption.soAllDirectories));
end;

GetFiles(dir, '*.JPEG *.BMP *.PNG *.GIF', TSearchOption.soAllDirectories)

uses System.IOUtils, System.Types;
....

const cFileMaskImages = '*.JPG;*.JPEG;*.BMP;*.PNG;*.GIF';


....
implementation

uses
  System.SysUtils, System.Masks, System.StrUtils;

function GetListDocs(Dir: String): TStringDynArray;
var
 Predicate: TDirectory.TFilterPredicate;
 MaskArray: TStringDynArray;
begin
  MaskArray := SplitString(cFileMaskImages, ';');

  Predicate :=
    function(const Path: string; const SearchRec: TSearchRec): Boolean
    var
      Mask: string;
    begin
      for Mask in MaskArray do
        if MatchesMask(SearchRec.Name, Mask) then
          exit(True);
      exit(False);
    end;


  result := TDirectory.GetFiles(dir, '*', TSearchOption.soAllDirectories, Predicate);
end;

function GetFileSize(const FileName: String): Int64;
var
  f: file of Byte;
begin
  try
    AssignFile(f, FileName);
    Reset(f);
    result := FileSize(f);
  finally
    CloseFile(f);
  end;
end;