/// <inheritdoc/> protected override void Dispose(bool disposing) { if (this.isDisposed) { return; } if (disposing) { // dispose managed resources this.deflateStream.Dispose(); // Add the crc uint crc = this.adler; this.rawStream.WriteByte((byte)((crc >> 24) & 0xFF)); this.rawStream.WriteByte((byte)((crc >> 16) & 0xFF)); this.rawStream.WriteByte((byte)((crc >> 8) & 0xFF)); this.rawStream.WriteByte((byte)(crc & 0xFF)); } this.deflateStream = null; base.Dispose(disposing); this.isDisposed = true; }
/// <summary> /// Initializes a new instance of the <see cref="ZlibDeflateStream"/> class. /// </summary> /// <param name="memoryAllocator">The memory allocator to use for buffer allocations.</param> /// <param name="stream">The stream to compress.</param> /// <param name="level">The compression level.</param> public ZlibDeflateStream(MemoryAllocator memoryAllocator, Stream stream, PngCompressionLevel level) { int compressionLevel = (int)level; this.rawStream = stream; // Write the zlib header : http://tools.ietf.org/html/rfc1950 // CMF(Compression Method and flags) // This byte is divided into a 4 - bit compression method and a // 4-bit information field depending on the compression method. // bits 0 to 3 CM Compression method // bits 4 to 7 CINFO Compression info // // 0 1 // +---+---+ // |CMF|FLG| // +---+---+ const int Cmf = 0x78; int flg = 218; // http://stackoverflow.com/a/2331025/277304 if (compressionLevel >= 5 && compressionLevel <= 6) { flg = 156; } else if (compressionLevel >= 3 && compressionLevel <= 4) { flg = 94; } else if (compressionLevel <= 2) { flg = 1; } // Just in case flg -= ((Cmf * 256) + flg) % 31; if (flg < 0) { flg += 31; } this.rawStream.WriteByte(Cmf); this.rawStream.WriteByte((byte)flg); this.deflateStream = new DeflaterOutputStream(memoryAllocator, this.rawStream, compressionLevel); }