Как узнать размер картинки для JPG, GIF и PNG файлов?

unit ImgSize;

interface

uses Classes;

procedure GetJPGSize(const sFile: string; var wWidth, wHeight: Word);
procedure GetPNGSize(const sFile: string; var wWidth, wHeight: Word);
procedure GetGIFSize(const sGIFFile: string; var wWidth, wHeight: Word);

implementation

uses SysUtils;

function ReadMWord(f: TFileStream): Word;
type
  TMotorolaWord = record
    case Byte of
      0: (Value: Word);
      1: (Byte1, Byte2: Byte);
  end;
var
  MW: TMotorolaWord;
begin
  { It would probably be better to just read these two bytes in normally }
  { and then do a small ASM routine to swap them.  But we aren't talking }
  { about reading entire files, so I doubt the performance gain would be }
  { worth the trouble. }
  f.Read(MW.Byte2, SizeOf(Byte));
  f.Read(MW.Byte1, SizeOf(Byte));
  Result := MW.Value;
end;

procedure GetJPGSize(const sFile: string; var wWidth, wHeight: Word);
const
  ValidSig: array[0..1] of Byte = ($FF, $D8);
  Parameterless = [$01, $D0, $D1, $D2, $D3, $D4, $D5, $D6, $D7];
var
  Sig: array[0..1] of Byte;
  f: TFileStream;
  x: Integer;
  Seg: Byte;
  Dummy: array[0..15] of Byte;
  Len: Word;
  ReadLen: LongInt;
begin
  FillChar(Sig, SizeOf(Sig), #0);
  f := TFileStream.Create(sFile, fmOpenRead);
  try
    ReadLen := f.Read(Sig[0], SizeOf(Sig));

    for x := Low(Sig) to High(Sig) do
      if Sig[x] <> ValidSig[x] then ReadLen := 0;

    if ReadLen > 0 then
    begin
      ReadLen := f.Read(Seg, 1);
      while (Seg = $FF) and (ReadLen > 0) do
      begin
        ReadLen := f.Read(Seg, 1);
        if Seg <> $FF then
        begin
          if (Seg = $C0) or (Seg = $C1) then
          begin
            ReadLen := f.Read(Dummy[0], 3); { don't need these bytes }
            wHeight := ReadMWord(f);
            wWidth  := ReadMWord(f);
          end
          else
          begin
            if not (Seg in Parameterless) then
            begin
              Len := ReadMWord(f);
              f.Seek(Len - 2, 1);
              f.read(Seg, 1);
            end
            else
              Seg := $FF; { Fake it to keep looping. }
          end;
        end;
      end;
    end;
  finally
    f.Free;
  end;
end;

procedure GetPNGSize(const sFile: string; var wWidth, wHeight: Word);
type
  TPNGSig = array[0..7] of Byte;
const
  ValidSig: TPNGSig = (137,80,78,71,13,10,26,10);
var
  Sig: TPNGSig;
  f: TFileStream;
  x: Integer;
begin
  FillChar(Sig, SizeOf(Sig), #0);
  f := TFileStream.Create(sFile, fmOpenRead);
  try
    f.Read(Sig[0], SizeOf(Sig));
    for x := Low(Sig) to High(Sig) do
      if Sig[x] <> ValidSig[x] then Exit;
    f.Seek(18, 0);
    wWidth := ReadMWord(f);
    f.Seek(22, 0);
    wHeight := ReadMWord(f);
  finally
    f.Free;
  end;
end;


procedure GetGIFSize(const sGIFFile: string; var wWidth, wHeight: Word);
type
  TGIFHeader = record
    Sig: array[0..5] of Char;
    ScreenWidth, ScreenHeight: Word;
    Flags, Background, Aspect: Byte;
  end;

  TGIFImageBlock = record
    Left, Top, Width, Height: Word;
    Flags: Byte;
  end;
var
  f: file;
  Header: TGifHeader;
  ImageBlock: TGifImageBlock;
  nResult: Integer;
  x: Integer;
  c: Char;
  DimensionsFound: Boolean;
begin
  wWidth  := 0;
  wHeight := 0;

  if sGifFile = '' then
    Exit;

  {$I-}
  FileMode := 0;   { read-only }
  AssignFile(f, sGifFile);
  Reset(f, 1);
  if IOResult <> 0 then
    { Could not open file }
    Exit;

  { Read header and ensure valid file. }
  BlockRead(f, Header, SizeOf(TGifHeader), nResult);
  if (nResult <> SizeOf(TGifHeader)) or (IOResult <> 0) or
    (StrLComp('GIF', Header.Sig, 3) <> 0) then
  begin
    { Image file invalid }
    Close(f);
    Exit;
  end;

  { Skip color map, if there is one }
  if (Header.Flags and $80) > 0 then
  begin
    x := 3 * (1 shl ((Header.Flags and 7) + 1));
    Seek(f, x);
    if IOResult <> 0 then
    begin
      { Color map thrashed }
      Close(f);
      Exit;
    end;
  end;

  DimensionsFound := False;
  FillChar(ImageBlock, SizeOf(TGIFImageBlock), #0);
  { Step through blocks. }
  BlockRead(f, c, 1, nResult);
  while (not EOF(f)) and (not DimensionsFound) do
  begin
    case c of
      ',': { Found image }
        begin
          BlockRead(f, ImageBlock, SizeOf(TGIFImageBlock), nResult);
          if nResult <> SizeOf(TGIFImageBlock) then
          begin
            { Invalid image block encountered }
            Close(f);
            Exit;
          end;
          wWidth := ImageBlock.Width;
          wHeight := ImageBlock.Height;
          DimensionsFound := True;
        end;
      'y': { Skip }
        begin
          { NOP }
        end;
      { nothing else.  just ignore }
    end;
    BlockRead(f, c, 1, nResult);
  end;
  Close(f);
  {$I+}
end;

end.

Source: http://www.swissdelphicenter.ch/en/tipsindex.php
ID: 04301

---

Размер Gif файла:

type
  TImageSize = record
    Width: Integer;
    Height: Integer;
  end;

function ReadGIFSize(Stream: TStream): TImageSize;
type
  TGifHeader = record
    Signature: array [0..5] of Char;
    Width, Height: Word;
  end;
var
  Header: TGifHeader;
begin
  FillChar(Header, SizeOf(TGifHeader), #0);
  Result.Width := -1;
  Result.Height := -1;
  with Stream do
  begin
    Seek(0, soFromBeginning);
    ReadBuffer(Header, SizeOf(TGifHeader));
  end;
  if (AnsiUpperCase(Header.Signature) = 'GIF89A') or
    (AnsiUpperCase(Header.Signature) = 'GIF87A') then
  begin
    Result.Width  := Header.Width;
    Result.Height := Header.Height;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
const
  FileName = 'D:\test.gif';
var
  fs: TFileStream;
  gifsize: TImageSize;
begin
  fs := TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);
  try
    gifsize := ReadGIFSize(fs);
    ShowMessage(Format('Breite %d Hohe %d', [gifsize.Width, gifsize.Height]));
  finally
    fs.Free;
  end;
end;

Source: http://www.swissdelphicenter.ch/en/tipsindex.php
ID: 04302