public static double[,] UncompressWithDCT(this CompressedImage image, int DCTSize)
        {
            var result = new double[image.Height, image.Width];

            var freqNum = 0;

            for (var y = 0; y < image.Height; y += DCTSize)
            {
                for (var x = 0; x < image.Width; x += DCTSize)
                {
                    var channelFreqs = new double[DCTSize, DCTSize];
                    for (var i = 0; i < DCTSize; i++)
                    {
                        for (var j = 0; j < DCTSize; j++)
                        {
                            if (i + j < image.CompressionLevel)
                            {
                                channelFreqs[i, j] = image.Frequences[freqNum++];
                            }
                        }
                    }
                    var processedSubmatrix = DCTTransformer.IDCT2D(channelFreqs);
                    processedSubmatrix.ShiftMatrixValues(128);
                    result.SetSubmatrix(processedSubmatrix, y, x);
                }
            }
            return(result);
        }
        public static double[,] ParallelUncompressWithDCT(this CompressedImage image, Options options)
        {
            const int DCTSize     = 8;
            var       result      = new double[image.Height, image.Width];
            var       blocksCount = image.Width * image.Height / (DCTSize * DCTSize);
            var       freqsCount  = Enumerable.Range(1, image.CompressionLevel).Sum();

            Parallel.For(0, blocksCount, new ParallelOptions {
                MaxDegreeOfParallelism = options.Threads
            },
                         blockIndex =>
            {
                var y            = blockIndex / (image.Width / DCTSize);
                var x            = blockIndex % (image.Width / DCTSize);
                var channelFreqs = new double[DCTSize, DCTSize];
                var freqNum      = blockIndex * freqsCount;

                for (var i = 0; i < DCTSize; i++)
                {
                    for (var j = 0; j < DCTSize; j++)
                    {
                        if (i + j < image.CompressionLevel)
                        {
                            channelFreqs[i, j] = image.Frequences[freqNum++];
                        }
                    }
                }
                var processedSubmatrix = DCTTransformer.IDCT2D(channelFreqs);
                processedSubmatrix.ShiftMatrixValues(128);
                result.SetSubmatrix(processedSubmatrix, y * DCTSize, x * DCTSize);
            });
            return(result);
        }