Delphi: Быстрое (де)кодирование JPEG с помощью libjpeg-turbo

unit suJpegTurboUnit;
 
interface
 
uses
  Windows, SysUtils,
 
  FastDIB;
 
type
  //Обработчик события которое возникает когда получен буфер с JPEG файлом
  TOnEncodedJpegBuffer = reference to procedure(ABuffer: Pointer; ABufferSize: LongWord);
 
  //Декодирование JPEG файла из буфера
  function DecodeJpegTurbo(ABuffer: Pointer; ABufferLen: Integer; HQ: Boolean = True): TFastDIB;
 
  //Кодирование JPEG
  procedure EncodeJpegTurbo(Source: TFastDIB; Quality: Integer; OnEncodedBuffer: TOnEncodedJpegBuffer);
 
implementation
 
uses
  suJpegTurboHeadersUnit,
  suJpegTurboMemDestUnit;
 
var
  _LibInitialized: LongBool = False;
 
//Обработчик критической ошибки
procedure ErrorExit(cinfo: j_common_ptr); cdecl;
var
  Msg: AnsiString;
begin
  //Получаем текст ошибки
  SetLength(Msg, JMSG_LENGTH_MAX);
  cinfo^.err^.format_message(cinfo, PAnsiChar(Msg));
 
  //Что бы обрезать мусор после #0 передаем Msg как PAnsiChar
  raise Exception.CreateFmt('JPEG error #%d (%s)',
    [cinfo^.err^.msg_code, PAnsiChar(Msg)]);
end;
 
//Обработчик вывода текста ошибки на экран
procedure OutputMessage(cinfo: j_common_ptr); cdecl;
begin
end;
 
//Инициализация библиотеки LibJpeg-Turbo
procedure InitLib;
begin
  if _LibInitialized then
    Exit;
 
  //Пробуем инициалировать
  if not init_libJPEG then
    raise Exception.Create('initialization of libJPEG failed.');
 
  //Запишем флаг что библиотека инициализированна
  if InterlockedCompareExchange(Integer(_LibInitialized), Integer(True), Integer(False)) = Integer(True) then
    //Если там уже записан этот флаг, значит другой поток инициализировал библиотеку
    //выгрузим свой экземпляр
    quit_libJPEG;
end;
 
//Декодирование
function DecodeJpegTurbo(ABuffer: pointer; ABufferLen: Integer; HQ: Boolean): TFastDIB;
var
  Loop: Integer;
  JpegErr: jpeg_error_mgr;
  Jpeg: jpeg_decompress_struct;
begin
  //Инициализация библиотеки
  InitLib;
 
  FillChar(Jpeg, SizeOf(Jpeg), 0);
  FillChar(JpegErr, SizeOf(JpegErr), 0);
 
  //Создаем структуру декомпрессора
  jpeg_create_decompress(@Jpeg);
  try
    //Назначим дефолтный обработчик ошибок
    Jpeg.err := jpeg_std_error(@JpegErr);
 
    //Переопределим методы дефолтного обработчика. По умолчанию, при возникновении
    //любой ошибки в LibJPEG происходит закрытие приложения, и вывод ошибки в MessageBox
    JpegErr.error_exit := ErrorExit;
    JpegErr.output_message := OutputMessage;
 
    jpeg_mem_src(@Jpeg, ABuffer, ABufferLen);
 
    //Прочитаем хидеры, дабы знать высоту и ширину картинки
    jpeg_read_header(@jpeg, False);
 
    //На выходе нужно получать пиксели BGR
    jpeg.out_color_space := JCS_EXT_BGR;
 
    //Настроим масштабирование - 1:1
    jpeg.scale_num := 1;
    jpeg.scale_denom := 1;
 
    //Скорость или хорошее качество
    If HQ then
    begin
      jpeg.do_block_smoothing := 1;
      jpeg.do_fancy_upsampling := 1;
      jpeg.dct_method := JDCT_ISLOW
    end
    else
    begin
      jpeg.do_block_smoothing := 0;
      jpeg.do_fancy_upsampling := 0;
      jpeg.dct_method := JDCT_IFAST;
    end;
 
    //Декодируем изображение
    jpeg_start_decompress(@Jpeg);
    try
      Result := TFastDIB.Create(jpeg.output_width, jpeg.output_height, 24);
      try
        //Читаем строки
        for Loop := 0 to jpeg.output_height - 1 do
          jpeg_read_scanlines(@jpeg, @Result.Scanlines[Result.Height - 1 - Loop], 1);
      except
        FreeAndNil(Result);
        raise;
      end;
    finally
      //Заканчиваем декодирование
      jpeg_finish_decompress(@Jpeg);
    end;
  finally
    //Уничтожаем ненужные объекты
    jpeg_destroy_decompress(@Jpeg);
  end;
end;
 
 
//Кодирование изображения
procedure EncodeJpegTurbo(Source: TFastDIB; Quality: Integer; OnEncodedBuffer: TOnEncodedJpegBuffer);
var
  ScanLine: JSAMPROW;
  CompressedBuff: Pointer;
  CompressedSize: LongWord;
  JpegErr: jpeg_error_mgr;
  Jpeg: jpeg_compress_struct;
begin
  //Инициализация библиотеки
  InitLib;
 
  FillChar(Jpeg, SizeOf(Jpeg), 0);
  FillChar(JpegErr, SizeOf(JpegErr), 0);
 
  //Создаем структуру компрессора
  jpeg_create_compress(@Jpeg);
  try
    //Назначим дефолтный обработчик ошибок
    Jpeg.err := jpeg_std_error(@JpegErr);
 
    //Переопределим методы дефолтного обработчика. По умолчанию, при возникновении
    //любой ошибки в LibJPEG происходит закрытие приложения, и вывод ошибки в MessageBox
    JpegErr.error_exit := ErrorExit;
    JpegErr.output_message := OutputMessage;
 
    CompressedSize := 0;
    CompressedBuff := nil;
 
    //Используем свою реализацию jpeg_mem_dest из-за утечек памяти в стандартной.
    suJpegTurboMemDestUnit.jpeg_mem_dest(@Jpeg, @CompressedBuff, @CompressedSize);
    try
      jpeg.image_width := Source.Width;
      jpeg.image_height := Source.Height;
      jpeg.input_components := Source.Info.Header.BitCount div 8;
      jpeg.in_color_space := JCS_EXT_BGR;
 
      //Setting defaults
      jpeg_set_defaults(@Jpeg);
 
      //Качество сжатия
      jpeg_set_quality(@Jpeg, Quality, True);
 
      //Декодируем изображение
      jpeg_start_compress(@Jpeg, True);
      try
        while Jpeg.next_scanline < Jpeg.image_height do
        begin
          ScanLine := JSAMPROW(Source.Scanlines[Jpeg.image_height - Jpeg.next_scanline - 1]);
          jpeg_write_scanlines(@Jpeg, @ScanLine, 1);
        end;
      finally
        //Заканчиваем кодирование
        jpeg_finish_compress(@Jpeg);
      end;
 
      //Передаем буфер вызывающей процедуре
      if Assigned(OnEncodedBuffer) then
        OnEncodedBuffer(CompressedBuff, CompressedSize);
    finally
      //Освободим память
      FreeMemory(CompressedBuff);
    end;
  finally
    //Уничтожаем ненужные объекты
    jpeg_destroy_compress(@Jpeg);
  end;
end;
 
initialization
 
finalization
  //Выгружаем если была загружена
  if _LibInitialized then
    quit_libJPEG;
end.

{
  Реализация аналога jpeg_mem_dest из JpegTurbo.
 
  Так как стандартная реализация требует после кодирования изображения освободить
  память RTL функцией Free (которая не экспортируется), к которой у нас нет доступа,
  пришлось написать аналог, который выделяет/освобождает память с помощью
  GetMemory/FreeMemory.
 
  Соответвенно, используя jpeg_mem_dest из данного модуля освобождать память с
  картинкой нужно стандартной FreeMemory.
 
  Код портирован на Delphi из jdatadst.c
}
unit suJpegTurboMemDestUnit;
 
interface
 
uses
  suJpegTurboHeadersUnit;
 
  procedure jpeg_mem_dest(cinfo: j_compress_ptr; outbuffer: PPointer; outsize: PLongWord);
 
implementation
 
const
  OUTPUT_BUF_SIZE  = 4096; //choose an efficiently fwrite'able size
 
type
  my_mem_destination_mgr = record
    pub: jpeg_destination_mgr;  //public fields
    outbuffer: PPointer; //target buffer
    outsize: PLongWord;
    newbuffer: Pointer;   //newly allocated buffer
    buffer: JOCTET_ptr; //start of buffer
    bufsize: LongWord;
  end;
  my_mem_dest_ptr = ^my_mem_destination_mgr;
 
//Initialize destination --- called by jpeg_start_compress
//before any data is actually written.
procedure init_mem_destination(cinfo: j_compress_ptr); cdecl;
begin
  //no work necessary here
end;
 
{
 Empty the output buffer --- called whenever buffer fills up.
 
 In typical applications, this should write the entire output buffer
 (ignoring the current state of next_output_byte & free_in_buffer),
 reset the pointer & count to the start of the buffer, and return TRUE
 indicating that the buffer has been dumped.
 
 In applications that need to be able to suspend compression due to output
 overrun, a FALSE return indicates that the buffer cannot be emptied now.
 In this situation, the compressor will return to its caller (possibly with
 an indication that it has not accepted all the supplied scanlines).  The
 application should resume compression after it has made more room in the
 output buffer.  Note that there are substantial restrictions on the use of
 suspension --- see the documentation.
 
 When suspending, the compressor will back up to a convenient restart point
 (typically the start of the current MCU). next_output_byte & free_in_buffer
 indicate where the restart point will be if the current call returns FALSE.
 Data beyond this point will be regenerated after resumption, so do not
 write it out when emptying the buffer externally.
}
function empty_mem_output_buffer(cinfo: j_compress_ptr): Boolean; cdecl;
var
  nextsize: LongWord;
  dest: my_mem_dest_ptr;
  nextbuffer: JOCTET_ptr;
begin
  dest := my_mem_dest_ptr(cinfo^.dest);
 
  //Try to allocate new buffer with double size
  nextsize := dest^.bufsize * 2;
  nextbuffer := GetMemory(nextsize);
 
  if nextbuffer = nil then
    ERREXIT1(j_common_ptr(cinfo), JERR_OUT_OF_MEMORY, 10);
 
  Move(dest^.buffer^, nextbuffer^, dest^.bufsize);
 
  if dest^.newbuffer <> nil then
    FreeMemory(dest^.newbuffer);
 
  dest^.newbuffer := nextbuffer;
 
  dest^.pub.next_output_byte := JOCTET_ptr(PByte(nextbuffer) + dest^.bufsize);
  dest^.pub.free_in_buffer := dest^.bufsize;
 
  dest^.buffer := nextbuffer;
  dest^.bufsize := nextsize;
 
  Result := True;
end;
 
procedure term_mem_destination(cinfo: j_compress_ptr); cdecl;
var
  dest: my_mem_dest_ptr;
begin
  dest := my_mem_dest_ptr(cinfo^.dest);
  dest^.outbuffer^ := dest^.buffer;
  dest^.outsize^ := dest^.bufsize - dest^.pub.free_in_buffer;
end;
 
{
  Prepare for output to a memory buffer.
  The caller may supply an own initial buffer with appropriate size.
  Otherwise, or when the actual data output exceeds the given size,
  the library adapts the buffer size as necessary.
  The standard library functions GetMemory/FreeMemory are used for allocating
  larger memory, so the buffer is available to the application after
  finishing compression, and then the application is responsible for
  freeing the requested memory.
}
procedure jpeg_mem_dest(cinfo: j_compress_ptr; outbuffer: PPointer; outsize: PLongWord);
var
  dest: my_mem_dest_ptr;
begin
  if (outbuffer = nil) or (outsize = nil) then
    ERREXIT(j_common_ptr(cinfo), JERR_BUFFER_SIZE);
 
  if (cinfo^.dest = nil) then //first time for this JPEG object?
    cinfo^.dest := cinfo^.mem.alloc_small(j_common_ptr(cinfo), JPOOL_PERMANENT,
      SizeOf(my_mem_destination_mgr));
 
  dest := my_mem_dest_ptr(cinfo^.dest);
  dest^.pub.init_destination := init_mem_destination;
  dest^.pub.empty_output_buffer := empty_mem_output_buffer;
  dest^.pub.term_destination := term_mem_destination;
  dest^.outbuffer := outbuffer;
  dest^.outsize := outsize;
  dest^.newbuffer := nil;
 
  if (outbuffer^ = nil) or (outsize^ = 0) then
  begin
    //Allocate initial buffer
    outbuffer^ := GetMemory(OUTPUT_BUF_SIZE);
 
    dest^.newbuffer := outbuffer^;
 
    if dest^.newbuffer = nil then
      ERREXIT1(j_common_ptr(cinfo), JERR_OUT_OF_MEMORY, 10);
 
    outsize^ := OUTPUT_BUF_SIZE;
  end;
 
  dest^.buffer := outbuffer^;
  dest^.pub.next_output_byte := dest^.buffer;
 
  dest^.bufsize := outsize^;
  dest^.pub.free_in_buffer := dest^.bufsize;
end;
 
end.

{ Known color spaces. }
 J_COLOR_SPACE = (
   JCS_UNKNOWN, { error/unspecified }
  JCS_GRAYSCALE,  //* monochrome */
  JCS_RGB,  //* red/green/blue as specified by the RGB_RED, RGB_GREEN,
      //RGB_BLUE, and RGB_PIXELSIZE macros */
  JCS_YCbCr,  //* Y/Cb/Cr (also known as YUV) */
  JCS_CMYK,  //* C/M/Y/K */
  JCS_YCCK,  //* Y/Cb/Cr/K */
  JCS_EXT_RGB,  //* red/green/blue */
  JCS_EXT_RGBX,  //* red/green/blue/x */
  JCS_EXT_BGR,  //* blue/green/red */
  JCS_EXT_BGRX,  //* blue/green/red/x */
  JCS_EXT_XBGR,  //* x/blue/green/red */
  JCS_EXT_XRGB,  //* x/red/green/blue */
//  When out_color_space it set to JCS_EXT_RGBX, JCS_EXT_BGRX,
//    JCS_EXT_XBGR, or JCS_EXT_XRGB during decompression, the X byte is
//    undefined, and in order to ensure the best performance,
//    libjpeg-turbo can set that byte to whatever value it wishes.  Use
//    the following colorspace constants to ensure that the X byte is set
//    to 0xFF, so that it can be interpreted as an opaque alpha
//    channel.
  JCS_EXT_RGBA,  ///* red/green/blue/alpha */
  JCS_EXT_BGRA,  //* blue/green/red/alpha */
  JCS_EXT_ABGR,  //* alpha/blue/green/red */
  JCS_EXT_ARGB  //* alpha/red/green/blue */
   );
 
...
 
 { Standard data source and destination managers: stdio streams. }
 { Caller is responsible for opening the file before and closing after. }
 // jpeg_stdio_dest: procedure(cinfo: j_compress_ptr; FILE * outfile); cdecl;
 // jpeg_stdio_src: procedure(cinfo: j_decompress_ptr; FILE * infile); cdecl;
 
 jpeg_mem_src: procedure(cinfo: j_decompress_ptr; inbuffer: Pointer; insize: LongWord); cdecl;
 jpeg_mem_dest: procedure(cinfo: j_decompress_ptr; outbuffer: Pointer; outsize: PLongWord); cdecl;
 
...
Function init_libJPEG(): boolean;
...
     @jpeg_mem_src := GetProcAddress(libJPEG_Handle, 'jpeg_mem_src');
     @jpeg_mem_dest := GetProcAddress(libJPEG_Handle, 'jpeg_mem_dest');
 
...
 {$DEFINE JPEG_LIB_VERSION = 62} //Version 6b
type
 J_MESSAGE_CODE = (
   JMSG_NOMESSAGE,
   {$IF Declared(JPEG_LIB_VERSION) and (JPEG_LIB_VERSION < 70)}
   JERR_ARITH_NOTIMPL,
   {$IFEND}
   JERR_BAD_ALIGN_TYPE,
   JERR_BAD_ALLOC_CHUNK,
   JERR_BAD_BUFFER_MODE,
   JERR_BAD_COMPONENT_ID,
   {$IF Declared(JPEG_LIB_VERSION) and (JPEG_LIB_VERSION >= 70)}
   JERR_BAD_CROP_SPEC,
   {$IFEND}
   JERR_BAD_DCT_COEF,
   JERR_BAD_DCTSIZE,
   {$IF Declared(JPEG_LIB_VERSION) and (JPEG_LIB_VERSION >= 70)}
   JERR_BAD_DROP_SAMPLING,
   {$IFEND}
   JERR_BAD_HUFF_TABLE,
   JERR_BAD_IN_COLORSPACE,
   JERR_BAD_J_COLORSPACE,
   JERR_BAD_LENGTH,
   JERR_BAD_LIB_VERSION,
   JERR_BAD_MCU_SIZE,
   JERR_BAD_POOL_ID,
   JERR_BAD_PRECISION,
   JERR_BAD_PROGRESSION,
   JERR_BAD_PROG_SCRIPT,
   JERR_BAD_SAMPLING,
   JERR_BAD_SCAN_SCRIPT,
   JERR_BAD_STATE,
   JERR_BAD_STRUCT_SIZE,
   JERR_BAD_VIRTUAL_ACCESS,
   JERR_BUFFER_SIZE,
   JERR_CANT_SUSPEND,
   JERR_CCIR601_NOTIMPL,
   JERR_COMPONENT_COUNT,
   JERR_CONVERSION_NOTIMPL,
   JERR_DAC_INDEX,
   JERR_DAC_VALUE,
   JERR_DHT_INDEX,
   JERR_DQT_INDEX,
   JERR_EMPTY_IMAGE,
   JERR_EMS_READ,
   JERR_EMS_WRITE,
   JERR_EOI_EXPECTED,
   JERR_FILE_READ,
   JERR_FILE_WRITE,
   JERR_FRACT_SAMPLE_NOTIMPL,
   JERR_HUFF_CLEN_OVERFLOW,
   JERR_HUFF_MISSING_CODE,
   JERR_IMAGE_TOO_BIG,
   JERR_INPUT_EMPTY,
   JERR_INPUT_EOF,
   JERR_MISMATCHED_QUANT_TABLE,
   JERR_MISSING_DATA,
   JERR_MODE_CHANGE,
   JERR_NOTIMPL,
   JERR_NOT_COMPILED,
   {$IF Declared(JPEG_LIB_VERSION) and (JPEG_LIB_VERSION >= 70)}
   JERR_NO_ARITH_TABLE,
   {$IFEND}
   JERR_NO_BACKING_STORE,
   JERR_NO_HUFF_TABLE,
   JERR_NO_IMAGE,
   JERR_NO_QUANT_TABLE,
   JERR_NO_SOI,
   JERR_OUT_OF_MEMORY,
   JERR_QUANT_COMPONENTS,
   JERR_QUANT_FEW_COLORS,
   JERR_QUANT_MANY_COLORS,
   JERR_SOF_DUPLICATE,
   JERR_SOF_NO_SOS,
   JERR_SOF_UNSUPPORTED,
   JERR_SOI_DUPLICATE,
   JERR_SOS_NO_SOF,
   JERR_TFILE_CREATE,
   JERR_TFILE_READ,
   JERR_TFILE_SEEK,
   JERR_TFILE_WRITE,
   JERR_TOO_LITTLE_DATA,
   JERR_UNKNOWN_MARKER,
   JERR_VIRTUAL_BUG,
   JERR_WIDTH_OVERFLOW,
   JERR_XMS_READ,
   JERR_XMS_WRITE
 );
 
procedure ERREXIT(cinfo: j_common_ptr; code: J_MESSAGE_CODE);
procedure ERREXIT1(cinfo: j_common_ptr; code: J_MESSAGE_CODE; p1: Integer);
 
...
 
//Макрос из jerror.h
//Fatal errors (print message and exit)
procedure ERREXIT(cinfo: j_common_ptr; code: J_MESSAGE_CODE);
begin
 cinfo^.err^.msg_code := Ord(code);
 cinfo^.err^.error_exit(j_common_ptr(cinfo));
end;
 
procedure ERREXIT1(cinfo: j_common_ptr; code: J_MESSAGE_CODE; p1: Integer);
begin
 cinfo^.err^.msg_code := Ord(code);
 cinfo^.err^.msg_parm.i[0] := p1;
 cinfo^.err^.error_exit(j_common_ptr(cinfo));
end;