Il backend Flate zlib-ng e coperto dalle suite di regressione automatiche Delphi e C++Builder. Il set di validazione corrente passa 20 test Delphi DUnitX su Win32 e 20 su Win64, piu 17 test C++Builder GoogleTest su Win32 e 17 su Win64x. Anche le ricompilazioni degli oggetti nativi passano da output puliti: 206 oggetti Win32, 205 oggetti Win64x e 206 oggetti MSVC Win64. I workflow coperti includono compressione page-stream, compressione font incorporati e ToUnicode CMap, stream immagine Flate, posizionamento immagini JPEG standard, import TIFF, output con molti barcode, scenari copy/merge/edit e PDF generati dalle demo

Compression Levels

• Z_NO_COMPRESSION (0): No compression
• Z_BEST_SPEED (1): Fastest compression
• Z_BEST_COMPRESSION (9): Maximum compression
• Z_DEFAULT_COMPRESSION (-1): Default balance of speed and compression

Usage Examples

Basic String Compression/Decompression

// Delphi example - Basic string inflation
function DecompressString(const CompressedData: AnsiString): AnsiString;
begin
  // Simple decompression
  Result := InflateStr(CompressedData);

  // With debug output enabled
  Result := InflateStr(CompressedData, True);
end;
        

Stream-based Compression

// Delphi example - Stream-based decompression
procedure DecompressStream(InStream, OutStream: TStream);
begin
  // Decompress from input stream to output stream
  PLZDecompressStream(InStream, OutStream);

  // For raw deflate data (without ZLib headers)
  PLZDecompressStreamRaw(InStream, OutStream);
end;
        

PDF FlateDecode with Parameters

// Delphi example - PDF FlateDecode with parameters
function DecompressPDFStream(const CompressedData: AnsiString;
  Predictor, Colors, BitsPerComponent, Columns: Integer): AnsiString;
var
  Parms: TPDFFlateParms;
begin
  // Configure PDF parameters
  Parms.Predictor := Predictor;
  Parms.Colors := Colors;
  Parms.BitsPerComponent := BitsPerComponent;
  Parms.Columns := Columns;
  Parms.ExpandedTo8Bit := True;
  Parms.ColorSpace := 'DeviceRGB';

  // Decompress with PDF parameters
  Result := InflateStrParms(CompressedData, Parms);
end;
        

Low-level ZLib Operations

// Delphi example - Low-level ZLib operations
procedure CompressData;
var
  strm: z_stream;
  ret: Integer;
  input: AnsiString;
  output: AnsiString;
begin
  input := 'Data to compress';
  SetLength(output, Length(input) * 2);

  // Initialize stream
  FillChar(strm, SizeOf(strm), 0);
  ret := deflateInit(strm, Z_DEFAULT_COMPRESSION);

  if ret = Z_OK then
  try
    // Set input
    strm.next_in := PByte(PAnsiChar(input));
    strm.avail_in := Length(input);

    // Set output
    strm.next_out := PByte(PAnsiChar(output));
    strm.avail_out := Length(output);

    // Compress
    ret := deflate(strm, Z_FINISH);

    if ret = Z_STREAM_END then
    begin
      // Compression successful
      SetLength(output, Length(output) - strm.avail_out);
    end;
  finally
    deflateEnd(strm);
  end;
end;
        

PDF FlateDecode Parameters

TPDFFlateParms Structure

• Predictor: Predictor function (1=no prediction, 2=TIFF, 10-15=PNG)
• Colors: Number of color components
• BitsPerComponent: Bits per color component
• Columns: Number of samples per row
• ExpandedTo8Bit: Whether to expand to 8-bit components
• ColorSpace: Color space identifier

Enhanced Features

• Memory Management: Optimized memory allocation and deallocation
• Error Handling: Comprehensive error checking and reporting
• Debug Support: Optional debug output for troubleshooting
• Performance Optimization: Highly optimized compression algorithms
• Stream Integration: Seamless integration with Delphi stream classes

Performance Benefits

• Fast compression and decompression speeds
• Excellent compression ratios for text and simple graphics
• Low memory footprint during processing
• Optimized for PDF content streams
• Minimal CPU overhead

Standards Compliance

• RFC 1950 (ZLib format specification)
• RFC 1951 (Deflate compression algorithm)
• PDF FlateDecode filter specification
• PNG predictor algorithm support
• TIFF predictor algorithm support

Error Codes and Handling

• Z_OK (0): Success
• Z_STREAM_END (1): End of stream reached
• Z_NEED_DICT (2): Dictionary required
• Z_ERRNO (-1): File error
• Z_STREAM_ERROR (-2): Stream state error
• Z_DATA_ERROR (-3): Data integrity error
• Z_MEM_ERROR (-4): Memory allocation error
• Z_BUF_ERROR (-5): Buffer size error

Vedi anche

• Supporto compressione LZW
• JBIG2 Compression
• THotPDF.Compression Property
• Compression Panoramica